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  • ENVIRONMENT POLLUTION  (11)
  • Biochemistry and Biotechnology  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The motion of algae in turbulent flow (1965)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 295-308 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Large cultures of microscopic, unicellular algae have been proposed as a means of maintaining a life-supporting atmosphere in a closed, manned system. To achieve vigorous growth of the algal culture it is necessary to subject individual algae alternately to short periods of high intensity light and darkness. One of the means suggested for obtaining a favorable light-dark sequence for photosynthesis is to cause turbulence in a closed channel on which light is incident. Since light is rapidly attenuated in a dense suspension, there will be illuminated regions adjacent to the channel walls and a dark central core. The random motions of turbulence normal to the direction of flow would move the algae alternately from the illuminated regions to the dark region and back again. This paper indicates a method for analyzing the motion of algae into and out of the illuminated region of a channel formed by flat, parallel, transparent plates, with light incident on the plates. Matching of a probability model with a diffusion model makes it possible to estimate the light-dark sequence which could be achieved by turbulence. The results indicate that favorable sequences by this mechanism are unlikely.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260070209
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Judgments of aircraft noise in a traffic noise background (1975)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: An investigation was conducted to determine subjective response to aircraft noise in different road traffic backgrounds. In addition, two laboratory techniques for presenting the aircraft noise with the background noise were evaluated. For one technique, the background noise was continuous over an entire test session; for the other, the background noise level was changed with each aircraft noise during a session. Subjective response to aircraft noise was found to decrease with increasing background noise level, for a range of typical indoor noise levels. Subjective response was found to be highly correlated with the Noise Pollution Level (NPL) measurement scale.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Sound and Vibration; 38; Jan. 8
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Effects of conversation interference on annoyance due to aircraft noise (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The annoyance and interference effects of aircraft flyover noise on face to face conversation were investigated. Twenty 5 minute sessions, each composed of three flyovers, were presented to each of 20 pairs of female subjects in a simulated living room. Flyovers varied in peak noise level (55-79 dB, A-weighted) and spectrum (low or high frequency components). Subjects engaged in conversation for 10 sessions and in reverie for the other 10 sessions, and completed subjective ratings following every session. Annoyance was affected by noise level, but was not significantly different for the two activities of reverie and conversation. A noise level of 77 db was found unacceptable for conversation by 50 percent of the subjects. Conversation interference was assessed by incidence of increased vocal effort and/or interruption of conversation during flyovers. Although conversation interference increased with noise level, the conversation interference measures did not improve prediction of individual annoyance judgments.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-TP-1712 , L-13709
    Format: application/pdf
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  • 4
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    Annoyance due to multiple airplane noise exposure (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A laboratory study was conducted to investigate the annoyance effects of multiple aircraft noise exposure in which 250 subjects judged the annoyance of half-hour periods of airplane noise simulative of typical indoor home exposures. The variables of the aircraft noise exposure were the peak noise level of flyovers, which was constant within each period, and the number of flyovers. Each subject judged 5 of the possible 25 factorial combinations of level and number. Other variables investigated included the experience of the test subjects in making annoyance judgments and their home exposure to airplane noise. The annoyance judgments increased with both noise level and number of flyovers. The increased annoyance produced by doubling the number of flyovers was found to be the equivalent of a 4 to 6 db increase in noise level. The sensitivity of the subjects to changes in both noise level and number of flyovers increased with laboratory experience. Although the means of the annoyance judgments made in the laboratory were found to decrease with the subjects' home exposure to aircraft noise, the subjects' sensitivities to changes in both level and number were unaffected by their home exposure.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-TP-1706 , L-13710
    Format: application/pdf
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  • 5
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    A subjective field study of helicopter blade-slap noise (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effects of impulsiveness on the noisiness of helicopters are examined by varying the main rotor speed while maintaining a constant airspeed. This resulted in other characteristics of the noise being held relatively constant. Other controlled variables included altitude, side line distance, descent operations, and level flyovers. A description is provided of the concept, experimental design and procedures along with results based on partial analyses of acoustic and subjective response data. No significant improvement in the noisiness predictive ability of EPNL was provided by either proposed or an A-weighted crest factor correction for impulsiveness.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-TM-78758
    Format: application/pdf
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  • 6
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    Effects of repetition rate and impulsiveness of simulated helicopter rotor noise on annoyance (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Annoyance judgements were obtained for computer generated stimuli simulative of helicopter impulsive rotor noise to investigate effects of repetition rate and impulsiveness. Each of the 82 different stimuli was judged at 3 sound pressure levels by 48 subjects. Impulse repetition rates covered a range from 10 Hz to 115 Hz; crest factors covered a range from 3.2 dB to 19.3 dB. Increases in annoyance with increases in repetition rate were found which were not predicted by common loudness or annoyance metrics and which were independent of noise level. The ability to predict effects of impulsiveness varied between the noise metrics and was found to be dependent on noise level. The ability to predict the effects of impulsiveness was not generally improved by any of several proposed impulsiveness corrections. Instead, the effects of impulsiveness were found to be systematically related to the frequency content of the stimuli. A modified frequency weighting was developed which offers improved annoyance prediction.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-TP-1969 , L-14936
    Format: application/pdf
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  • 7
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    Effects of activity interference on annoyance due to aircraft noise (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effects of aircraft flyover noise on annoyance were compared for face to face conversation, reverie, and television viewing. Eighteen 5 minute sessions, each composed of three flyovers, were presented on each of 2 days to subjects in a simulated living room. Twelve pairs of females and 12 pairs of males were tested, once before and once after work. Flyovers varied in peak noise level from 53 to 83 dB, A weighted. On each day, subjects engaged in 18 sessions, six of conversation, six of television viewing, and six of reverie. The subjects completed subjective ratings of annoyance and acceptability following every session. Annoyance and unacceptability rating scores were significantly higher for the activity of television viewing compared to conversation or reverie. There was no difference between judgments during the latter two activities. No differences were found in the judgments when compared on the basis of "fatigue" (before/after work) or sex of the subject.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-TP-1938 , L-14808
    Format: application/pdf
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  • 8
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    Multiple-event airplane noise annoyance (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The annoyance of sessions of airplane noise which contained different noise levels and numbers of flyovers was investigated. The time of occurrence of the high noise level flyovers in the sessions did not significantly affect annoyance, but annoyance increased with the number of such flyovers. Annoyance decreased with test session duration but increased with the total number of flyovers in the test sessions. It is found that the results support an average energy model better than a total energy model, the annoyance decay model, or the dB(A) peak concept.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-TP-2101 , L-15517 , NAS 1.60:2101
    Format: application/pdf
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  • 9
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    A summation and inhibition model of annoyance response to multiple community noise sources (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A model of annoyance due to combined noise sources was developed. The model provides for the summation of the subjective magnitudes of annoyance due to the separate noise sources and for the inhibition of the subjective magnitudes of each source by the presence of the other noise sources. The inhibition process is assumed to mathematically obey a power-group transformation. The results of an experiment in which subjects judged the annoyance of 15 minute sessions of combined aircraft and with several other models of combined source annoyance. These comparisons indicated that the model developed herein provides better qualitative and quantitative agreement with experimental responses than the other models. The application of the model to multiple community noises is discussed.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-TP-1479 , L-12978
    Format: application/pdf
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  • 10
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    Laboratory study of annoyance to combined airplane and road-traffic noise (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The annoyance of noise, which consisted of both separate and combined airplane and road-traffic noises, was studied. The subjects judged each session as to how annoyed they were in the simulated living room laboratory environment and as to how annoyed they were if they heard the noise in their home during day, evening, and night periods. The airplane noises, for equal session levels were judged significantly more annoying than the road traffic noises for the separate sessions. For the combined sessions, an interaction was found between the airplane noise and traffic noise levels, which was not adequately assessed by the total energy concept. Significant differences were found between the projected home responses for the day, evening, and night periods.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-TP-1478 , L-12977
    Format: application/pdf
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