ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Publication Date: 2017-04-04
    Description: In recent years, an increasing number of surveys have definitively confirmed the seasonal presence of fin whales (Balaenoptera physalus) in highly productive regions of the Mediterranean Sea. Despite this, very little is yet known about the routes that the species seasonally follows within the Mediterranean basin and, particularly, in the Ionian area. The present study assesses for the first time fin whale acoustic presence offshore Eastern Sicily (Ionian Sea), throughout the processing of about 10 months of continuous acoustic monitoring. The recording of fin whale vocalizations was made possible by the cabled deep-sea multidisciplinary observatory, “NEMO-SN1”, deployed 25 km off the Catania harbor at a depth of about 2,100 meters. NEMO-SN1 is an operational node of the European Multidisciplinary Seafloor and water-column Observatory (EMSO) Research Infrastructure. The observatory was equipped with a low-frequency hydrophone (bandwidth: 0.05 Hz–1 kHz, sampling rate: 2 kHz) which continuously acquired data from July 2012 to May 2013. About 7,200 hours of acoustic data were analyzed by means of spectrogram display. Calls with the typical structure and patterns associated to the Mediterranean fin whale population were identified and monitored in the area for the first time. Furthermore, a background noise analysis within the fin whale communication frequency band (17.9–22.5 Hz) was conducted to investigate possible detection-masking effects. The study confirms the hypothesis that fin whales are present in the Ionian Sea throughout all seasons, with peaks in call detection rate during spring and summer months. The analysis also demonstrates that calls were more frequently detected in low background noise conditions. Further analysis will be performed to understand whether observed levels of noise limit the acoustic detection of the fin whales vocalizations, or whether the animals vocalize less in the presence of high background noise.
    Description: Published
    Description: e0141838
    Description: 3A. Ambiente Marino
    Description: JCR Journal
    Description: open
    Keywords: Whales ; Bioacoustics ; Background noise (acoustics) ; Acoustic signals ; Sperm whales ; Vocalization ; Acoustics ; Data acquisition ; 03. Hydrosphere::03.01. General::03.01.08. Instruments and techniques ; 03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring ; 03. Hydrosphere::03.02. Hydrology::03.02.07. Instruments and techniques ; 03. Hydrosphere::03.04. Chemical and biological::03.04.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2016-03-05
    Description: Observing marine mammal (MM) populations continuously in time and space over the immense ocean areas they inhabit is challenging but essential for gathering an unambiguous record of their distribution, as well as understanding their behaviour and interaction with prey species. Here we use passive ocean acoustic waveguide remote sensing (POAWRS) in an important North Atlantic feeding ground to instantaneously detect, localize and classify MM vocalizations from diverse species over an approximately 100,000 km(2) region. More than eight species of vocal MMs are found to spatially converge on fish spawning areas containing massive densely populated herring shoals at night-time and diffuse herring distributions during daytime. We find the vocal MMs divide the enormous fish prey field into species-specific foraging areas with varying degrees of spatial overlap, maintained for at least two weeks of the herring spawning period. The recorded vocalization rates are diel (24 h)-dependent for all MM species, with some significantly more vocal at night and others more vocal during the day. The four key baleen whale species of the region: fin, humpback, blue and minke have vocalization rate trends that are highly correlated to trends in fish shoaling density and to each other over the diel cycle. These results reveal the temporospatial dynamics of combined multi-species MM foraging activities in the vicinity of an extensive fish prey field that forms a massive ecological hotspot, and would be unattainable with conventional methodologies. Understanding MM behaviour and distributions is essential for management of marine ecosystems and for accessing anthropogenic impacts on these protected marine species.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wang, Delin -- Garcia, Heriberto -- Huang, Wei -- Tran, Duong D -- Jain, Ankita D -- Yi, Dong Hoon -- Gong, Zheng -- Jech, J Michael -- Godo, Olav Rune -- Makris, Nicholas C -- Ratilal, Purnima -- England -- Nature. 2016 Mar 17;531(7594):366-70. doi: 10.1038/nature16960. Epub 2016 Mar 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory for Ocean Acoustics and Ecosystem Sensing, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, USA. ; Laboratory for Undersea Remote Sensing, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA. ; Northeast Fisheries Science Center, 166 Water Street, Woods Hole, Massachusetts 02543, USA. ; Institute of Marine Research, Post Office Box 1870, Nordnes, N-5817 Bergen, Norway.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26934221" target="_blank"〉PubMed〈/a〉
    Keywords: Acoustics ; Animals ; Aquatic Organisms/*physiology ; Atlantic Ocean ; Diet/veterinary ; Ecosystem ; *Feeding Behavior ; Fishes/*physiology ; Male ; Mammals/*physiology ; *Predatory Behavior ; Time Factors ; *Vocalization, Animal ; Whales/physiology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2019-07-19
    Description: The current vibro-acoustic analysis tools require specific spatial correlation parameters as input to define the liftoff acoustic environment experienced by the launch vehicle. Until recently these parameters have not been very well defined. A comprehensive set of spatial correlation data were obtained during a scale model acoustic test conducted in 2014. From these spatial correlation data, several parameters were calculated: the decay coefficient, the diffuse to propagating ratio, and the angle of incidence. Spatial correlation data were also collected on the EFT-1 flight of the Delta IV vehicle which launched on December 5th, 2014. A comparison of the spatial correlation parameters from full scale and model scale data will be presented.
    Keywords: Acoustics
    Type: M16-5412 , Acoustical Society of America; Nov 28, 2016 - Dec 02, 2016; Honolulu, HI; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Acoustics
    Type: JSC-CN-37440 , International Association for the Advancement of Space Safety; Sep 02, 2016; Noordwijk; Netherlands
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2019-07-13
    Description: The effect of finite span on the jet-surface interaction noise source and the jet mixing noise shielding and reflection effects is considered using recently acquired experimental data. First, the experimental setup and resulting data are presented with particular attention to the role of surface span on far-field noise. These effects are then included in existing empirical models that have previously assumed that all surfaces are semi-infinite. This extended abstract briefly describes the experimental setup and data leaving the empirical modeling aspects for the final paper.
    Keywords: Acoustics
    Type: GRC-E-DAA-TN28948 , SciTech 2016 Conference; Jan 04, 2016 - Jan 08, 2016; San Diego, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2019-07-13
    Description: Proposed uses of small unmanned aerial vehicles (UAVs), including home package delivery, have the potential to expose large portions of communities to a new noise source. This paper discusses results of flyover noise measurements of four small UAVs, including an internal combustion-powered model airplane and three battery-powered multicopters. Basic noise characteristics of these vehicles are discussed, including spectral properties and sound level metrics such as sound pressure level, effective perceived noise level, and sound exposure level. The size and aerodynamic characteristics of the multicopters in particular make their flight path susceptible to atmospheric disturbances such as wind gusts. These gusts, coupled with a flight control system that varies rotor speed to maintain vehicle stability, create an unsteady acoustic signature. The spectral variations resulting from this unsteadiness are explored, in both hover and flyover conditions for the multicopters. The time varying noise, which differs from the relatively steady noise generated by large transport aircraft, may complicate the prediction of human annoyance using conventional sound level metrics.
    Keywords: Acoustics
    Type: nc16-102 , NF1676L-23558 , NOISE-CON 2016; Jun 13, 2016 - Jun 15, 2016; Providence, RI; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2019-07-13
    Description: The effect of finite span on the jet-surface interaction noise source and the jet mixing noise shielding and reflection effects is considered using recently acquired experimental data. First, the experimental setup and resulting data are presented with particular attention to the role of surface span on far-field noise. These effects are then included in existing empirical models that have previously assumed that all surfaces are semi-infinite. This extended abstract briefly describes the experimental setup and data leaving the empirical modeling aspects for the final paper.
    Keywords: Acoustics
    Type: NASA/TM-2016-219096 , AIAA Paper 2016-0006 , E-19225 , GRC-E-DAA-TN30559 , Scitech 2016; Jan 04, 2016 - Jan 08, 2016; San Diego, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2019-07-12
    Description: The present technology is directed to methods of soft tissue emulsification using a mechanism of ultrasonic atomization inside gas or vapor cavities, and associated systems and devices. In several embodiments, for example, a method of non-invasively treating tissue includes pulsing ultrasound energy from the ultrasound source toward the target site in tissue. The ultrasound source is configured to emit high intensity focused ultrasound (HIFU) waves. The target site comprises a pressure-release interface of a gas or vapor cavity located within the tissue. The method continues by generating shock waves in the tissue to induce a lesion in the tissue at the target site. The method additionally includes characterizing the lesion based on a degree of at least one of a mechanical or thermal ablation of the tissue.
    Keywords: Acoustics
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2019-07-12
    Description: This report summarizes results of the Hybrid Wing Body (HWB) N2A-EXTE model aeroacoustic test. The N2A-EXTE model was tested in the NASA Langley 14- by 22-Foot Subsonic Tunnel (14x22 Tunnel) from September 12, 2012 until January 28, 2013 and was designated as test T598. This document contains the following main sections: Section 1 - Introduction, Section 2 - Main Personnel, Section 3 - Test Equipment, Section 4 - Data Acquisition Systems, Section 5 - Instrumentation and Calibration, Section 6 - Test Matrix, Section 7 - Data Processing, and Section 8 - Summary. Due to the amount of material to be documented, this HWB test documentation report does not cover analysis of acquired data, which is to be presented separately by the principal investigators. Also, no attempt was made to include preliminary risk reduction tests (such as Broadband Engine Noise Simulator and Compact Jet Engine Simulator characterization tests, shielding measurement technique studies, and speaker calibration method studies), which were performed in support of this HWB test. Separate reports containing these preliminary tests are referenced where applicable.
    Keywords: Acoustics
    Type: NASA/TM-2016-219185 , L-20425 , NF1676L-19028
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2019-07-12
    Description: Dr. Fereidoun 'Feri' Farassat was a theoretical aero-acoustician at the National Aeronautics and Space Administration (NASA) Langley Research Center. This book contains technical derivations, notes, and classes that Dr. Farassat produced during his professional career. The layout of the book has been carefully crafted so that foundational ideas through advanced theories, which altered the technical discipline of aeroacoustics, build upon one another. The book can be used to understand the theories of acoustics and learn one contemporary aeroacoustic prediction approach made popular by Dr. Farassat. Most importantly, this book gives the general reader insight into how one of NASA's best aeroacoustics theoreticians thought, constructed, and solved problems throughout his career.
    Keywords: Acoustics
    Type: NASA/TM-2016-219179 , L-20663 , NF1676L-23594
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    Publication Date: 2019-07-12
    Description: A cooperative flight test campaign between NASA and the U.S. Army was performed from September 2014 to February 2015. The purposes of the testing were to: investigate the effects of altitude variation on noise generation, investigate the effects of gross weight variation on noise generation, establish the statistical variability in acoustic flight testing of helicopters, and characterize the effects of transient maneuvers on radiated noise for a medium-lift utility helicopter. This test was performed at three test sites (0, 4000, and 7000 feet above mean sea level) with two aircraft (AS350 SD1 and EH-60L) tested at each site. This report provides an overview of the test, documents the data acquired and describes the formats of the stored data.
    Keywords: Acoustics
    Type: NASA/TM-2016-219354 , L-20729 , NF1676L-24899
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Publication Date: 2019-07-12
    Description: This report documents acoustic testing of tuned chamber core panels, which can be used to supplement the low-frequency performance of conventional acoustic treatment. The tuned chamber core concept incorporates low-frequency noise control directly within the primary structure and is applicable to sandwich constructions with a directional core, including corrugated-, truss-, and fluted-core designs. These types of sandwich structures have long, hollow channels (or chambers) in the core. By adding small holes through one of the facesheets, the hollow chambers can be utilized as an array of low-frequency acoustic resonators. These resonators can then be used to attenuate low-frequency noise (below 400 Hz) inside a vehicle compartment without increasing the weight or size of the structure. The results of this test program demonstrate that the tuned chamber core concept is effective when used in isolation or combined with acoustic foam treatments. Specifically, an array of acoustic resonators integrated within the core of the panels was shown to improve both the low-frequency absorption and transmission loss of the structure in targeted one-third octave bands.
    Keywords: Acoustics
    Type: NASA/TM-2016-219338 , L-20748 , NF1676L-25375
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Publication Date: 2019-08-24
    Description: An apparatus and method for vibration suppression using a granular particle chain. The granular particle chain is statically compressed and the end particles of the chain are attached to a payload and vibration source. The properties of the granular particles along with the amount of static compression are chosen to provide desired filtering of vibrations.
    Keywords: Acoustics
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Publication Date: 2019-08-24
    Description: A surface acoustic wave (SAW)-based coherence multiplexing system includes SAW tags each including a SAW transducer, a first SAW reflector positioned a first distance from the SAW transducer and a second SAW reflector positioned a second distance from the SAW transducer. A transceiver including a wireless transmitter has a signal source providing a source signal and circuitry for transmitting interrogation pulses including a first and a second interrogation pulse toward the SAW tags, and a wireless receiver for receiving and processing response signals from the SAW tags. The receiver receives scrambled signals including a convolution of the wideband interrogation pulses with response signals from the SAW tags and includes a computing device which implements an algorithm that correlates the interrogation pulses or the source signal before transmitting against the scrambled signals to generate tag responses for each of the SAW tags.
    Keywords: Acoustics
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Publication Date: 2019-08-28
    Description: An interactive liner design and impedance modeling tool comprises software utilized to design acoustic liners for use in constrained spaces, both regularly and irregularly shaped. A graphical user interface allows the acoustic channel geometry to be drawn in a liner volume while the surface impedance calculations are updated and displayed in real-time. A one-dimensional transmission line model may be used as the basis for the impedance calculations.
    Keywords: Acoustics
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Publication Date: 2019-08-28
    Description: A slat cove filler is utilized to reduce airframe noise resulting from deployment of a leading edge slat of an aircraft wing. The slat cove filler is preferably made of a super elastic shape memory alloy, and the slat cove filler shifts between stowed and deployed shapes as the slat is deployed. The slat cove filler may be configured such that a separate powered actuator is not required to change the shape of the slat cove filler from its deployed shape to its stowed shape and vice-versa. The outer contour of the slat cove filler preferably follows a profile designed to maintain accelerating flow in the gap between the slat cove filler and wing leading edge to provide for noise reduction.
    Keywords: Acoustics
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Publication Date: 2020-01-08
    Description: No abstract available
    Keywords: Acoustics
    Type: JPL-CL-16-3683 , SPIE Optics and Photonics; Aug 01, 2016 - Sep 01, 2016; San Diego, CA; United States
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Publication Date: 2020-01-07
    Description: No abstract available
    Keywords: Acoustics
    Type: JPL-CL-16-2580 , Spacecraft and Launch Vehicle Workshop; Jun 21, 2016 - Jun 23, 2016; El Segundo, CA; United States
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Publication Date: 2019-07-13
    Description: Light diffraction from ultrasound, which can be used to investigate nonlinear acoustic phenomena in liquids, is reported for wave amplitudes larger than that typically reported in the literature. Large amplitude waves result in waveform distortion due to the nonlinearity of the medium that generates harmonics and produces asymmetries in the light diffraction pattern. For standing waves with amplitudes above a threshold value, subharmonics are generated in addition to the harmonics and produce additional diffraction orders of the incident light. With increasing drive amplitude above the threshold a cascade of period-doubling subharmonics are generated, terminating in a region characterized by a random, incoherent (chaotic) diffraction pattern. To explain the experimental results a toy model is introduced, which is derived from traveling wave solutions of the nonlinear wave equation corresponding to the fundamental and second harmonic standing waves. The toy model reduces the nonlinear partial differential equation to a mathematically more tractable nonlinear ordinary differential equation. The model predicts the experimentally observed cascade of period-doubling subharmonics terminating in chaos that occurs with increasing drive amplitudes above the threshold value. The calculated threshold amplitude is consistent with the value estimated from the experimental data.
    Keywords: Acoustics
    Type: NF1676L-23450 , International Congress on Acoustics; Sep 05, 2016 - Sep 09, 2016; Buenos Aires; Argentina
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Publication Date: 2019-07-13
    Description: Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.
    Keywords: Acoustics
    Type: NF1676L-23461 , 2016 IEEE International Conference on Prognostics and Health Management; Jun 20, 2016 - Jun 22, 2016; Ottawa, Ontario; Canada
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    Publication Date: 2019-07-13
    Description: Several approaches to active noise control using virtual sensors are evaluated for eventual use in an active headrest. Specifically, adaptive feedforward, feedback, and hybrid control structures are compared. Each controller incorporates the traditional filtered-x least mean squares algorithm. The feedback controller is arranged in an internal model configuration to draw comparisons with standard feedforward control theory results. Simulation and experimental results are presented that illustrate each controllers ability to minimize the pressure at both physical and virtual microphone locations. The remote microphone technique is used to obtain pressure estimates at the virtual locations. It is shown that a hybrid controller offers performance benefits over the traditional feedforward and feedback controllers. Stability issues associated with feedback and hybrid controllers are also addressed. Experimental results show that 15-20 dB reduction in broadband disturbances can be achieved by minimizing the measured pressure, whereas 10-15 dB reduction is obtained when minimizing the estimated pressure at a virtual location.
    Keywords: Acoustics
    Type: NF1676L-23534 , NOISE-CON 2016; Jun 13, 2016 - Jun 15, 2016; Providence, RI; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    Publication Date: 2019-07-13
    Description: Aircraft system noise is predicted for a portfolio of NASA advanced concepts with 2025 entry-into-service technology assumptions. The subsonic transport concepts include tube-and-wing configurations with engines mounted under the wing, over the wing nacelle integration, and a double deck fuselage with engines at a mid-fuselage location. Also included are hybrid wing body aircraft with engines upstream of the fuselage trailing edge. Both advanced direct drive engines and geared turbofan engines are modeled. Recent acoustic experimental information was utilized in the prediction for several key technologies. The 301-passenger class hybrid wing body with geared ultra high bypass engines is assessed at 40.3 EPNLdB cumulative below the Stage 4 certification level. Other hybrid wing body and unconventional tube-and-wing configurations reach levels of 33 EPNLdB or more below the certification level. Many factors contribute to the system level result; however, the hybrid wing body in the 301-passenger class, as compared to a tubeand- wing with conventional engine under wing installation, has 11.9 EPNLdB of noise reduction due to replacing reflection with acoustic shielding of engine noise sources. Therefore, the propulsion airframe aeroacoustic interaction effects clearly differentiate the unconventional configurations that approach levels close to or exceed the 42 EPNLdB goal.
    Keywords: Acoustics
    Type: NF1676L-21515 , AIAA SciTech Conference; Jan 04, 2016 - Jan 08, 2016; San Diego, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Publication Date: 2019-07-13
    Description: The effect of finite span on the jet-surface interaction noise source and the jet mixing noise shielding and reflection effects is considered using recently acquired experimental data. First, the experimental setup and resulting data are presented with particular attention to the role of surface span on far-field noise. These effects are then included in existing empirical models that have previously assumed that all surfaces are semi-infinite. This extended abstract briefly describes the experimental setup and data leaving the empirical modeling aspects for the final paper.
    Keywords: Acoustics
    Type: GRC-E-DAA-TN28447 , SciTech 2016 Conference; Jan 04, 2016 - Jan 08, 2016; San Diego, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    Publication Date: 2019-07-13
    Description: Velocimetry measurements were obtained in three-stream jets at the NASA Glenn Research Center Nozzle Acoustics Test Rig using the time-resolved Doppler global velocimetry technique. These measurements afford exceptional frequency response, to 125 kHz bandwidth, in order to study the detailed dynamics of turbulence in developing shear flows. Mean stream-wise velocity is compared to measurements acquired using particle image velocimetry for validation. Detailed results for convective velocity distributions throughout an axisymmetric plume and the thick side of a plume with an offset third-stream duct are provided. The convective velocity results exhibit that, as expected, the eddy speeds are reduced on the thick side of the plume compared to the axisymmetric case. The results indicate that the time-resolved Doppler global velocimetry method holds promise for obtaining results valuable to the implementation and refinement of jet noise prediction methods being developed for three-stream jets.
    Keywords: Acoustics
    Type: GRC-E-DAA-TN29011 , AIAA Science and Technology Forum and Exposition (AIAA SciTech); Jan 04, 2016 - Jan 08, 2016; San Diego, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    Publication Date: 2019-07-13
    Description: Results of a psychoacoustic test performed to understand the relative annoyance to noise produced by several configurations of a distributed electric propulsion high lift system are given. It is found that the number of propellers in the system is a major factor in annoyance perception. This is an intuitive result as annoyance increases, in general, with frequency, and, the blade passage frequency of the propellers increases with the number of propellers. Additionally, the data indicate that having some variation in the blade passage frequency from propeller-to-propeller is beneficial as it reduces the high tonality generated when all the propellers are spinning in synchrony at the same speed. The propellers can be set to spin at different speeds, but it was found that allowing the motor controllers to drift within 1% of nominal settings produced the best results (lowest overall annoyance). The methodology employed has been demonstrated to be effective in providing timely feedback to designers in the early stages of design development.
    Keywords: Acoustics
    Type: NF1676L-22771 , AIAA Aviation 2016; Jun 13, 2016 - Jun 17, 2016; Washington, DC; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Acoustics
    Type: NF1676L-23507 , Acoustical Society of America Spring 2016 Meeting; May 23, 2016 - May 27, 2016; Salt Lake City, UT; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    Publication Date: 2019-07-13
    Description: Commercial supersonic flight is currently forbidden over land because sonic booms have historically caused unacceptable annoyance levels in overflown communities. NASA is providing data and expertise to noise regulators as they consider relaxing the ban for future quiet supersonic aircraft. One key objective is a predictive model for indoor annoyance based on factors such as noise and indoor vibration levels. The current study quantified the increment in indoor sonic boom annoyance when sonic booms can be felt directly through structural vibrations in addition to being heard. A shaker mounted below each chair in the sonic boom simulator emulated vibrations transmitting through the structure to that chair. The vibration amplitudes were determined from numeric models of a large range of residential structures excited by the same sonic boom waveforms used in the experiment. The analysis yielded vibration penalties, which are the increments in sound level needed to increase annoyance as much as the vibration does. For sonic booms at acoustic levels from 75 to 84 dB Perceived Level, vibration signals with lower amplitudes (+1 sigma) yielded penalties from 0 to 5 dB, and vibration signals with higher amplitudes (+3 sigma) yielded penalties from 6 to 10 dB.
    Keywords: Acoustics
    Type: NF1676L-23460 , Spring 2016 Meeting Acoustical Society of America; May 23, 2016 - May 27, 2016; Salt Lake City, UT; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    Publication Date: 2019-07-13
    Description: Aircraft system noise predictions have been performed for NASA modeled hybrid wing body aircraft advanced concepts with 2025 entry-into-service technology assumptions. The system noise predictions developed over a period from 2009 to 2016 as a result of improved modeling of the aircraft concepts, design changes, technology development, flight path modeling, and the use of extensive integrated system level experimental data. In addition, the system noise prediction models and process have been improved in many ways. An additional process is developed here for quantifying the uncertainty with a 95% confidence level. This uncertainty applies only to the aircraft system noise prediction process. For three points in time during this period, the vehicle designs, technologies, and noise prediction process are documented. For each of the three predictions, and with the information available at each of those points in time, the uncertainty is quantified using the direct Monte Carlo method with 10,000 simulations. For the prediction of cumulative noise of an advanced aircraft at the conceptual level of design, the total uncertainty band has been reduced from 12.2 to 9.6 EPNL dB. A value of 3.6 EPNL dB is proposed as the lower limit of uncertainty possible for the cumulative system noise prediction of an advanced aircraft concept.
    Keywords: Acoustics
    Type: NF1676L-22657 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    Publication Date: 2019-07-13
    Description: The potential of significantly reducing aircraft landing gear noise is explored for aircraft configurations with engines installed above the wings or the fuselage. An innovative concept is studied that does not alter the main gear assembly itself but does shorten the main strut and integrates the gear in pods whose interior surfaces are treated with acoustic liner. The concept is meant to achieve maximum noise reduction so that main landing gears can be eliminated as a major source of airframe noise. By applying this concept to an aircraft configuration with 2025 entry-into-service technology levels, it is shown that compared to noise levels of current technology, the main gear noise can be reduced by 10 EPNL dB, bringing the main gear noise close to a floor established by other components such as the nose gear. The assessment of the noise reduction potential accounts for design features for the advanced aircraft configuration and includes the effects of local flow velocity in and around the pods, gear noise reflection from the airframe, and reflection and attenuation from acoustic liner treatment on pod surfaces and doors. A technical roadmap for maturing this concept is discussed, and the possible drag increase at cruise due to the addition of the pods is identified as a challenge, which needs to be quantified and minimized possibly with the combination of detailed design and application of drag reduction technologies.
    Keywords: Acoustics
    Type: NF1676L-22681 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    Publication Date: 2019-07-13
    Description: This paper presents the development of a noise prediction model for aircraft Krueger flap devices that are considered as alternatives to leading edge slotted slats. The prediction model decomposes the total Krueger noise into four components, generated by the unsteady flows, respectively, in the cove under the pressure side surface of the Krueger, in the gap between the Krueger trailing edge and the main wing, around the brackets supporting the Krueger device, and around the cavity on the lower side of the main wing. For each noise component, the modeling follows a physics-based approach that aims at capturing the dominant noise-generating features in the flow and developing correlations between the noise and the flow parameters that control the noise generation processes. The far field noise is modeled using each of the four noise component's respective spectral functions, far field directivities, Mach number dependencies, component amplitudes, and other parametric trends. Preliminary validations are carried out by using small scale experimental data, and two applications are discussed; one for conventional aircraft and the other for advanced configurations. The former focuses on the parametric trends of Krueger noise on design parameters, while the latter reveals its importance in relation to other airframe noise components.
    Keywords: Acoustics
    Type: NF1676L-22682 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    Publication Date: 2019-07-13
    Description: A method for educing the locally-reacting acoustic impedance of a test sample mounted in a 3-D normal incidence impedance tube is presented and validated. The unique feature of the method is that the excitation frequency (or duct geometry) may be such that high-order duct modes may exist. The method educes the impedance, iteratively, by minimizing an objective function consisting of the difference between the measured and numerically computed acoustic pressure at preselected measurement points in the duct. The method is validated on planar and high-order mode sources with data synthesized from exact mode theory. These data are then subjected to random jitter to simulate the effects of measurement uncertainties on the educed impedance spectrum. The primary conclusions of the study are 1) Without random jitter the method is in excellent agreement with that for known impedance samples, and 2) Random jitter that is compatible to that found in a typical experiment has minimal impact on the accuracy of the educed impedance.
    Keywords: Acoustics
    Type: NF1676L-22697 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    Publication Date: 2019-07-13
    Description: A high fidelity aeroacoustic test was conducted in the NASA Langley 14- by 22-Foot Subsonic Tunnel to establish a detailed database of component noise for a 5.8% scale HWB aircraft configuration. The model has a modular design, which includes a drooped and a stowed wing leading edge, deflectable elevons, twin verticals, and a landing gear system with geometrically scaled wheel-wells. The model is mounted inverted in the test section and noise measurements are acquired at different streamwise stations from an overhead microphone phased array and from overhead and sideline microphones. Noise source distribution maps and component noise spectra are presented for airframe configurations representing two different approach flight conditions. Array measurements performed along the aircraft flyover line show the main landing gear to be the dominant contributor to the total airframe noise, followed by the nose gear, the inboard side-edges of the LE droop, the wing tip/LE droop outboard side-edges, and the side-edges of deployed elevons. Velocity dependence and flyover directivity are presented for the main noise components. Decorrelation effects from turbulence scattering on spectral levels measured with the microphone phased array are discussed. Finally, noise directivity maps obtained from the overhead and sideline microphone measurements for the landing gear system are provided for a broad range of observer locations.
    Keywords: Acoustics
    Type: NF1676L-22760 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Acoustics
    Type: AIAA Paper 2016-3041 , NF1676L-22789 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    Publication Date: 2019-07-13
    Description: This study explores the effects of liner length and attenuation on the CHE (convected Helmholtz equation) impedance eduction method, in which the surface impedance of an acoustic liner is inferred through an iterative process based on repeated solutions to the convected Helmholtz equation. Wire mesh-over-honeycomb and perforate-over-honeycomb acoustic liners are tested in the NASA Langley Grazing Flow Impedance Tube, and the resultant data are processed using two impedance eduction methods. The first is the CHE method, and the second is a direct method (labeled the KT method) that uses the Kumaresan and Tufts algorithm to compute the impedance directly. The CHE method has been extensively used for acoustic liner evaluation, but experiences anomalous behavior under some test conditions. It is postulated that the anomalies are related to the liner length and/or attenuation. Since the KT method only employs data measured over the length of the liner, it is expected to be unaffected by liner length. A comparison of results achieved with the two impedance eduction methods is used to explore the interactive effects of liner length and attenuation on the CHE impedance eduction method.
    Keywords: Acoustics
    Type: AIAA Paper 2016-2782 , NF1676L-22804 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    Publication Date: 2019-07-13
    Description: Auralization of aircraft flyover noise provides an auditory experience that complements integrated metrics obtained from system noise predictions. Recent efforts have focused on auralization methods development, specifically the process by which source noise information obtained from semi-empirical models, computational aeroacoustic analyses, and wind tunnel and flight test data, are used for simulated flyover noise at a receiver on the ground. The primary focus of this work, however, is to develop full vehicle auralizations in order to explore the distinguishing features of NASA's N+2 aircraft vis--vis current fleet reference vehicles for single-aisle and large twin-aisle classes. Some features can be seen in metric time histories associated with aircraft noise certification, e.g., tone-corrected perceived noise level used in the calculation of effective perceived noise level. Other features can be observed in sound quality metrics, e.g., loudness, sharpness, roughness, fluctuation strength and tone-to-noise ratio. A psychoacoustic annoyance model is employed to establish the relationship between sound quality metrics and noise certification metrics. Finally, the auralizations will serve as the basis for a separate psychoacoustic study aimed at assessing how well aircraft noise certification metrics predict human annoyance for these advanced vehicle concepts.
    Keywords: Acoustics
    Type: NF1676L-22859 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    Publication Date: 2019-07-13
    Description: This paper presents a review of four novel liner concepts: soft vanes, over-the-rotor liners, external liners, and flap side-edge liners. A number of similarities in the design and evaluation of these concepts emerged during these investigations. Since these were the first attempts to study these particular liner concepts, there was limited information to guide the design process. In all cases, the target frequencies (or frequency range) were known, but the optimum acoustic impedance and optimum liner placement were typically not known. For these cases, the maximum available surface was used and a c-impedance was targeted based on the assumption the sound field impinges on the surface at normal incidence. This choice proved fruitful for every application. An impedance prediction model was used to design variable-depth liner configurations, and a graphical design code (ILIAD) was developed to aid in this process. The ability to build increasingly complex liner configurations via additive manufacturing was key, such that multiple designs could quickly be tested in a normal incidence impedance tube. The Two-Thickness Method was used to evaluate available bulk materials, such that bulk liners could also be considered for each application. These novel liner concepts provide sufficient noise reduction to warrant further investigations.
    Keywords: Acoustics
    Type: NF1676L-22808 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    Publication Date: 2019-07-13
    Description: The utilization of advanced fan designs (including higher bypass ratios) and shorter engine nacelles has highlighted a need for increased fan noise reduction over a broader frequency range. Thus, improved broadband liner designs must account for these constraints and, where applicable, take advantage of advanced manufacturing techniques that have opened new possibilities for novel configurations. This work focuses on the use of an established broadband acoustic liner optimization process to design a variable-depth, multi-degree of freedom liner for a high speed fan. Specifically, in-duct attenuation predictions with a statistical source model are used to obtain optimum impedance spectra over the conditions of interest. The predicted optimum impedance information is then used with acoustic liner modeling tools to design a liner aimed at producing impedance spectra that most closely match the predicted optimum values. The multi-degree of freedom design is carried through design, fabrication, and testing. In-duct attenuation predictions compare well with measured data and the multi-degree of freedom liner is shown to outperform a more conventional liner over a range of flow conditions. These promising results provide further confidence in the design tool, as well as the enhancements made to the overall design process.
    Keywords: Acoustics
    Type: NF1676L-22922 , AIAA/CEAS Aeroacoustis Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Publication Date: 2019-07-13
    Description: A new aeroacoustic measurement capability has been developed consisting of a large channelcount, field-deployable microphone phased array suitable for airframe noise flyover measurements for a range of aircraft types and scales. The array incorporates up to 185 hardened, weather-resistant sensors suitable for outdoor use. A custom 4-mA current loop receiver circuit with temperature compensation was developed to power the sensors over extended cable lengths with minimal degradation of the signal to noise ratio and frequency response. Extensive laboratory calibrations and environmental testing of the sensors were conducted to verify the design's performance specifications. A compact data system combining sensor power, signal conditioning, and digitization was assembled for use with the array. Complementing the data system is a robust analysis system capable of near real-time presentation of beamformed and deconvolved contour plots and integrated spectra obtained from array data acquired during flyover passes. Additional instrumentation systems needed to process the array data were also assembled. These include a commercial weather station and a video monitoring / recording system. A detailed mock-up of the instrumentation suite (phased array, weather station, and data processor) was performed in the NASA Langley Acoustic Development Laboratory to vet the system performance. The first deployment of the system occurred at Finnegan Airfield at Fort A.P. Hill where the array was utilized to measure the vehicle noise from a number of sUAS (small Unmanned Aerial System) aircraft. A unique in-situ calibration method for the array microphones using a hovering aerial sound source was attempted for the first time during the deployment.
    Keywords: Acoustics
    Type: NF1676L-23031 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    Publication Date: 2019-07-13
    Description: Microphone phased array acoustic measurements of a 26 percent-scale, Boeing 777-200 main landing gear model with and without noise reduction fairings installed were obtained in the anechoic configuration of the Virginia Tech Stability Tunnel. Data were acquired at Mach numbers of 0.12, 0.15, and 0.17 with the latter speed used as the nominal test condition. The fully and partially dressed gear with the truck angle set at 13 degrees toe-up landing configuration were the two most extensively tested configurations, serving as the baselines for comparison purposes. Acoustic measurements were also acquired for the same two baseline configurations with the truck angle set at 0 degrees. In addition, a previously tested noise reducing, toboggan-shaped fairing was re-evaluated extensively to address some of the lingering questions regarding the extent of acoustic benefit achievable with this device. The integrated spectra generated from the acoustic source maps reconfirm, in general terms, the previously reported noise reduction performance of the toboggan fairing as installed on an isolated gear. With the recent improvements to the Virginia Tech tunnel acoustic quality and microphone array capabilities, the present measurements provide an additional, higher quality database to the acoustic information available for this gear model.
    Keywords: Acoustics
    Type: AIAA Paper 2016-2091 , NF1676L-23033 , AIAA/CEAS Aeroacoustics Conference; May 30, 2016 - Jun 01, 2016; Lyon; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    Publication Date: 2019-07-13
    Description: This paper presents an overview of a flight test campaign performed at different test sites whose altitudes ranged from 0 to 7000 feet above mean sea level (AMSL) between September 2014 and February 2015. The purposes of this campaign were to: investigate the effects of altitude variation on noise generation, investigate the effects of gross weight variation on noise generation, establish the statistical variability in acoustic flight testing of helicopters, and characterize the effects of transient maneuvers on radiated noise for a medium-lift utility helicopter. In addition to describing the test campaign, results of the acoustic effects of altitude variation for the AS350 SD1 and EH-60L aircraft are presented. Large changes in acoustic amplitudes were observed in response to changes in ambient conditions when the helicopter was flown at constant indicated airspeed and gross weight at the three test sites. However, acoustic amplitudes were found to scale with ambient pressure when flight conditions were defined in terms of the non-dimensional parameters, such as the weight coefficient and effective hover tip Mach number.
    Keywords: Acoustics
    Type: NF1676L-22567 , American Helicopter Society (AHS) Annual Forum; May 17, 2016 - May 19, 2016; West Palm Beach, FL; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    Publication Date: 2019-07-13
    Description: In an effort to mitigate next-generation fuel efficiency and environmental impact concerns for aviation, open rotor propulsion systems have received renewed interest. However, maintaining the high propulsive efficiency while simultaneously meeting noise goals has been one of the challenges in making open rotor propulsion a viable option. Improvements in prediction tools and design methodologies have opened the design space for next generation open rotor designs that satisfy these challenging objectives. As such, validation of aerodynamic and acoustic prediction tools has been an important aspect of open rotor research efforts. This paper describes validation efforts of a combined computational fluid dynamics and Ffowcs Williams and Hawkings equation methodology for open rotor aeroacoustic modeling. Performance and acoustic predictions were made for a benchmark open rotor blade set and compared with measurements over a range of rotor speeds and observer angles. Overall, the results indicate that the computational approach is acceptable for assessing low-noise open rotor designs. Additionally, this approach may be used to provide realistic incident source fields for acoustic shielding/scattering studies on various aircraft configurations.
    Keywords: Acoustics
    Type: NF1676L-21693 , AIAA Aerospace Sciences Meeting; Jan 04, 2016 - Jan 08, 2016; San Diego, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    Publication Date: 2019-07-13
    Description: Detailed acoustic measurements of the noise from the leading-edge Krueger flap of a 5.75 percent Hybrid Wing Body (HWB) aircraft model were recently acquired with a traversing phased microphone array in the AEDC NFAC (Arnold Engineering Development Complex, National Full Scale Aerodynamics Complex) 40- by 80-Foot Wind Tunnel at NASA Ames Research Center. The spatial resolution of the array was sufficient to distinguish between individual support brackets over the full-scale frequency range of 100 to 2875 Hertz. For conditions representative of landing and take-off configuration, the noise from the brackets dominated other sources near the leading edge. Inclusion of flight-like brackets for select conditions highlights the importance of including the correct number of leading-edge high-lift device brackets with sufficient scale and fidelity. These measurements will support the development of new predictive models.
    Keywords: Acoustics
    Type: ARC-E-DAA-TN28059 , AIAA SciTech 2016; Jan 04, 2016 - Jan 08, 2016; San Diego, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    Publication Date: 2019-07-13
    Description: This paper focuses on the adaptation mechanisms in adaptive hybrid controllers. Most adaptive hybrid controllers update two filters individually according to the filtered-reference least mean squares (FxLMS) algorithm. Because this algorithm was derived for feedforward control, it does not take into account the presence of a feedback loop in the gradient calculation. This paper provides a derivation of the proper weight vector gradient for hybrid (or feedback) controllers that takes into account the presence of feedback. In this formulation, a single weight vector is updated rather than two individually. An internal model structure is assumed for the feedback part of the controller. The full gradient is equivalent to that used in the standard FxLMS algorithm with the addition of a recursive term that is a function of the modeling error. Some simulations are provided to highlight the advantages of using the full gradient in the weight vector update rather than the approximation.
    Keywords: Acoustics
    Type: Paper 5pNSa7 , NF1676L-26473 , Proceedings of Meetings on Acoustics; 29|Joint Meeting of the Acoustical Society of America and Acoustical Society of Japan; Nov 28, 2016 - Dec 02, 2016; Honolulu, HI; United States|Meeting of the Acoustical Society of America. Design of Noise Control Materials; Nov 28, 2016 - Dec 02, 2016; Honolulu, HI; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    Publication Date: 2019-07-13
    Description: The Jet-Surface Interaction High Aspect Ratio Nozzle Test was conducted in the Aero-Acoustic Propulsion Laboratory at the NASA Glenn Research Center in the fall of 2015. There were four primary goals specified for this test: (1) extend the current noise database for rectangular nozzles to higher aspect ratios, (2) verify data previously acquired at small-scale with data from a larger model, (3) acquired jet-surface interaction noise data suitable for creating verifying empirical noise models and (4) investigate the effect of nozzle septa on the jet-mixing and jet-surface interaction noise. These slides give a summary of the test with representative results for each goal.
    Keywords: Acoustics
    Type: GRC-E-DAA-TN31570 , Acoustics Technical Working Group Meeting; Apr 19, 2016 - Apr 20, 2016; Hampton, VA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-07-12
    Description: This manual documents the Aircraft NOise Prediction Program 2 (ANOPP2). ANOPP2 is a toolkit that includes a framework, noise prediction methods, and peripheral software to aid a user in predicting and understanding aircraft noise. This manual includes an explanation of the overall design and structure of ANOPP2, including a brief introduction to aircraft noise prediction and the ANOPP2 background, philosophy, and architecture. The concept of nested acoustic data surfaces and its application to a mixed-fidelity noise prediction are presented. The structure and usage of ANOPP2, which includes the communication between the user, the ANOPP2 framework, and noise prediction methods, are presented for two scenarios: wind-tunnel and flight. These scenarios serve to provide the user with guidance and documentation references for performing a noise prediction using ANOPP2.
    Keywords: Acoustics
    Type: NASA/TM-2016-219342 , L-20692 , NF1676L-24083
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    Publication Date: 2019-07-12
    Description: This Technical Publication summarizes the work focused on the testing and analysis of sensor ports. The tasks under this contract were divided into three areas: (1) Development of an Analytical Model, (2) Conducting a Set of Experiments, and (3) Obtaining Computational Solutions. Results from the experiment using both short and long sensor ports were obtained using harmonic, random, and frequency sweep plane acoustic waves. An amplification factor of the pressure signal between the port inlet and the back of the port is obtained and compared to models. Comparisons of model and experimental results showed very good agreement.
    Keywords: Acoustics
    Type: NASA/TP-2016-218222 , M-1412 , M16-5288
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    Publication Date: 2019-07-12
    Description: In support of the ongoing effort by the National Aeronautics and Space Administration (NASA) to bring supersonic commercial travel to the public, the NASA Armstrong Flight Research Center (AFRC) and the NASA Langley Research Center (LaRC), in partnership with other industry organizations and academia, conducted a flight research experiment to analyze acoustic propagation at the lateral edge of the sonic boom carpet. The name of the effort was the Farfield Investigation of No-boom Thresholds (FaINT). The test helped to build a dataset that will go toward further understanding of the unique acoustic propagation characteristics near the sonic boom carpet extremity. The FaINT was an effort that collected finely-space sonic boom data across the entire lateral cutoff transition region. A major objective of the effort was to investigate the acoustic phenomena that occur at the audible edge of a sonic boom carpet, including the transition and shadow zones. A NASA F-18B aircraft made supersonic passes such that its sonic boom carpet transition zone would intersect a linear 60-microphone, 7500-ft long array. A TG-14 motor glider equipped with a microphone on its wing also attempted to capture the same sonic boom rays that were measured on the ground, at altitudes of 3000 - 6000 ft above ground level. This paper determined an appropriate metric for sonic boom waveforms in the transition and shadow zones called Perceived Sound Exposure Level, and established a value of 65 dB as a limit for the acoustic levels defining the lateral extent of a sonic boom's noise region; analyzed the change in sonic boom levels as a function of distance from flight path both on the ground and 4500 ft above the ground; and compared between sonic boom measurements and numerical predictions.
    Keywords: Acoustics
    Type: NASA/TM-2016-218850 , DFRC-E-DAA-TN25061
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    facet.materialart.
    Unknown
    In:  Journ. Acoust. Soc. Am., Tokyo, Terra Scientific Publishing Company, vol. 17, no. 1, pp. 109, pp. B03312, (ISBN: 0534351875, 2nd edition)
    Publication Date: 1945
    Keywords: Instruments ; Filter- ; Acoustics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...