ALBERT

Description: Digital computing techniques have been used in special computing applications in underwater acoustics at WHOI for many years, but recently we have commenced intensive application of digital data handling and computing facilities to a variety of computing, data storage, and data handling problems. Progress in these applications is described under Acoustic Instrumentation below. Some bathymetric studies carried out recently under another contract have shown that even very narrow-beam, single-beam echo sounders simply cannot provide reliable depth sounding information where the topography is complex. In this work we have been experimenting with the inverted echo sounder, discussed below, originally developed to measure depth of the sound velocimeter. The inverted echo sounder is lowered to a position within a few feet of the bottom. The total acoustic travel time from surface to bottom may be read as the sum of the travel times from the instrument to the bottom and surface . True depth is then computed in the usual way with appropriate s cnmd velocity data. In its present form the inverted echo sounder is suitable for mapping ~mall areas~ a few square miles, provided there is a suitable means of positioning the instrument. We have experimented with radio-acoustic navigation, and intend to experiment with vertical triangulation from the suspending ship as well. Steady demands for new, modified, and improved instrumentation have been responded to in echo sounding, seismic profiling, and spectrum analysis, as detailed below.

Description: Undersea Warfare Branch Office of Naval Research Under Contracts Nonr-1367(00)NR261-102 and Nonr-2129(00)NR261-104

Description: This i s a status report for the period 1 May 1966 to 31 October 1966 for Contract Nonr - 4029 with the Office of Naval Research. Subjects of this contract are in Oceanic Acoustics, Physical Oceanography, Sea Floor Properties and Advisory Activities. Preliminary results of a cruise by CHAIN to the Mediterranean and the Red Sea during the summer of 1966 are given. Sound-velocity and temperature structure south of Bermuda as observed from ATLANTIS II (June, July 1966) are described. Continuing analysis of acoustical and geophysical data is discussed. Papers, reports, and technical memoranda written during this period are listed.

Description: The Undersea Warfare Branch., Office of Naval Research., under Contract.Nonr-4029(00) NR 260-101.

Description: This is a report of the research program under contracts Nonr-4029 (1 May - 31 October 1963), and Nonr-3243 (1 May - 31 October 1963} . Both contracts are with the Office of Naval Research, Code 466. Contract Nonr-4029 is a continuation of Contract Nonr-1367. Under Contract Nonr-4029, ATLANTIS· II and CHAIN, in May and August, were employed in searching for the sunken submarine THRESHER by various means. Under the same contract, activities were devoted also to the development of systems or components of systems for search and for navigational control required in such operations. One system of submerged navigation was employed for locating suspended instruments by acoustic ranging from the ship. A second navigation system was also tested which depends on acoustic ranging either from the ship or from the suspended instrument to a hydrophone buoyed near the bottom. This hydrophone is connected to a radio link in a surface buoy. This system will be useful not only for navigation but also for bottom reflection studies. A program has been started to print and mount all photos taken by WHOI on the THRESHER search; it will be coordinated with other similar efforts in the continuing investigation of the disaster. Under Contracts Nonr-4029 and Nonr-3243 considerable progress has been made in other research, which is described in this report .

Description: Submitted to Under sea Warfare Branch Office of Naval Research Under· Contracts Nonr- 4029(00)NR261-10 2 and Nonr- 3243(00) NR261-136

Description: This is a report of activities supported under Contract NObsr-72521 for the period 1 January through 31 March 1961. It also contains mention of other reports, papers, and undertakings of the submarine geophysics group (listed under "Personnel") which are believed to be of interest to the Bureau of Ships. During this period no cruises have been supported directly under this contract. Eight members of the group under the leadership of Dr. Voorhis have participated in a cruise of CHAIN to the Romanche Trench. Their principal objective was to determine the sill depth which controls the exchange of deep, cold water ,between the western and eastern sides of the Atlantic Ocean. This sill was previously identified from hydrographic evidence to lie somewhat east of the Romanche Trench. A second objective was to continue the observations of temperature structure near the sea's surface with the thermistor chain. Another group, under Mr. Baxter's leadership, continued a sound transmission study in the Bermuda area in support of Project ARTEMIS. A third group, under Dr. Hays's direction, commenced a finely detailed bathymetric survey of an area of special interest to Project ARTEMIS. In all three of these studies we are making use of one or more experimental techniques in the use of sonobuoys, underwater acoustic navigation for submerged instruments, and sound coherence studies which are planned for use eventually in sound transmission and bottom reflection research under this contract.

Description: Bureau of Ships Under Contract NObsr-72521

Description: Research at sea during this three month period, supported by Contract NObsr-72521, was carried out mostly during the latter portion of the CHAIN Cruise 21 to the eastern Mediterranean. Near-surface sound transmission runs were made with the aid of two foreign ships in the eastern Mediterranean and Tyrrhenian Sea. Sound velocity measurements were made there also. Reverberation and back-scatter measurements using half pound explosives as sound sources were recorded on magnetic tape for future analysis. Further, at several places during the cruise acoustic reflectivity of the sea-floor was measured by means of a semi-automatic system employing the Precision Graphic Recorder and the Edo UQN Echo Sounder. Research other than that on CHAIN Cruise 21, included ambient noise studies of recorded signals from finback whales, and analysis of data from previous observations at sea.

Description: The Bureau of Ships Under Contract NObsr - 72521

Description: Geophysical investigations were carried out aboard R /V CHAIN in the Indian Ocean, the Mediterranean Sea, and the North Atlantic Ocean. Observations underway were continuous seismic profiling, gravity, magnetic, and echo sounding measurements. At stations rocks were dredged, cores were taken (about 10 meters long, photographic montages of the sea floor were made, and the sound velocity of the water was measured as a function of depth. Progress is being made in filtering and correlation techniques for seismic profiling, while seismic receiving arrays were improved to make them quieter. The analysis of internal wave data is continuing, but further observations at sea will be required in order to fully understand the mechanism of propagation. Seven papers were published during this period and thirteen were submitted for publication. These papers are concerned with seismic profiling, seismic refraction profiles, sediment ponding, sound transmission, thermal fronts, and biological papers dealing with sound production by marine mammals and deep-sea fish natural history gained from bottom photographs. A new thermistor string intended to replace and improve upon the original thermistor chain was the principal new instrumental development.

Description: Undersea Warfare Branch Office of Naval Research under Contracts Nonr-4029(00)NR260-101 and Nonr-3243(00)NR260-108

Description: Experiments are described to demonstrate a new method of sonic signalling at extremely long ranges in the oceans, utilizing the natural sound channel. Signals were made by causing a four pound charge of TNT to explode at about 4000 feet depth. These signals have the following qualities: (a) Extremely long range transmission (probably 10,000 miles). (b) Signal is positively identifiable. (c) Abrupt termination of the signal allows the arrival time to be read with an accuracy better than l/20th second. This permits location of source to better than a mile, if the signal is received at three suitably located stations. (d) The signal duration is related in such a way to the distance that the distance may be estimated to 30 miles in 1000 from reception at a single station. The limitations are: (a) It is required that the great circle path which the sound follows between source and receiver lie entirely in deep water (probably at least 1000 fathoms). (b) Sound travels in water at a speed of roughly 1 mile per second so that the interval between the origin of the signal and its reception becomes sufficiently great to be a handicap for some uses, particularly with aircraft. The signals were received to distances up to 900 miles. Two receiving arrangements have been used, a hydrophone hung 4000 feet over the side of a ship which was hove to, and a shore connected. hydrophone which lay on bottom 4000 feet deep. Extrapolation of the results indicate a range of at least 10,000 miles from this size charge. Recommendation is made to utilize a network of monitoring stations to locate planes, ships, and life rafts in distress on the open oceans. Three or more stations receiving a signal could locate the source better than one mile.

Description: Con tract NObs - 2083, Formerly OEM: sr - 31

Description: This is a progress report of the Institution's research between April and 30 June 1961 supported under Contract NObsr-72521 with the Bureau of Ships, Navy Department. The program consists of studies of compressional wave transmission (sound and seismic waves) through sea water and the underlying earth's crust, the ambient noise of the ocean, and the scattering of sound in the sea and beneath the ocean floor. During the present reporting period sound transmission studies have included laboratory analysis of data taken previously in a continuing program directed toward describing near-surface transmission into the shadow zone, and toward accounting for the variability of near-surface . transmission under nominally "good" sonar conditions . Seismic studies consisted of analysis of seismic refraction data taken two years ago in: the Mediterranean, completion of a report of a seismic reflection study of the southern part of Narragansett Bay, extension of this latter study into Rhode Island Sound, and a series of new measurements of the apparent reflectivity of the bottom at 12 kcps. In the sound-scattering program we accepted delivery of a small towed fish containing sound gear for scattering experiments over near-horizontal paths. This instrument was taken to sea on CHAIN for initial testing and self-noise measurements. A series of tests of new sound sources, supported under Contract Nonr-1367, have demonstrated that seismic reflection observations can be made in deep ocean basins from a ship underway slowly using only such electrically-powered sources as Thumper or Sparker. Sub-bottom structures have been mapped in fine detail experimentally in water over 2600 fathoms deep. This work was done with a Thumper having a 5000-joule electrical input . Plans have been made for increasing the electrical input of Thumper to about 13, 000 joules and Sparker to 25, 000 joules. We plan to use these new sound sources in sound transmission experiments this summer and fall in the Mediterranean Sea. As an extra-curricular hobby Miss Broughton, a technical assistant at the Institution, made interesting magnetic tape recordings of the sounds of a small pilot whale stranded on a local beach. She held microphones on the whale's head near the blow hole. The recorded sounds are rather different from those heard through the water near pilot whales. These and other parts of our work are detailed below.

Description: Bureau of Ships Under Contract NObsr-72521

Description: This is a status report for the six-month's period indicated. It includes the closing phase of a long cruise of CHAIN to the Mediterranean Sea during which circulation of the waters of the eastern Mediterranean were studied and sound transmission, seismic reflection, and shallow thermal structure measurements were made at various places in the Mediterranean and the North Atlantic. During the remainder of the period various geophysical, geological, and hydroacoustical analyses were conducted at Woods Hole and preparations for the summer cruising season were made.

Description: The Undersea Warfare Branch Office of Naval Research Under Contracts Nonr - 1367 (OO)NR261-102 and Nonr-2129(00)NR261-104

Description: Research during this six month period was performed during cruises of the CHAIN to the Romanche Trench, to the Puerto Rico Trench, and to the Mediterranean Sea, and during a cruise of the BEAR to the Gulf of Maine. New instrumentation aboard the CHAIN included the 12, 000 joule Boomer and a 25, 000 joule Sparker for continuous Seismic reflection profiles and other research in hydroacoustics. A semiautomatic data recording system for shipboard use was in.stalled and operated by IBM and, to facilitate launching and retrieving deep gear, a closed circuit television system was used . Also the navigational system, GEON, was installed and tested. Prior to the cruises of the summer and fall redesign and refinement of the instrumentation and equipment entailed overhaul of the thermistor chain and contouring temperature recorder, modification of the heat probe for thermal gradient measurements to lessen lowering time, and improvement of the inverted echo-sounding equipment. Research at sea included collecting samples of rock and sediment and photographing the ocean floor in support of research into the structure and dynamics of the Romanche and Puerto Rico Trenches and the Mid-Atlantic Ridge , observing internal waves in the North Atlantic studying water circulation in the Mediterranean, the dynamics of flow through the Strait of Gibraltar (concentrating this year on internal waves there), observing the behavior and measuring the sound scattering properties of deep scattering layers in the Mediterranean, measuring heat flow from the inner Earth across the Mid-Atlantic Ridge and in the western Mediterranean, and studying the relationship between sound transmission and the physical properties of the water and sea floor in the eastern Mediterranean. At Woods Hole various analysis programs progressed. Several of these used programs of digital computing which have been prepared lately at Woods Hole. The precision time source for remote control reported earlier was improved and tested ashore. A tape recording system for Scuba divers was devised and tested satisfactorily in thirty feet of water.

Description: Undersea Warfare Branch Office of Naval Research Contracts Nonr-1367(00)NR 261-102 and Nonr-2129(00)NR 261-104

Description: Measurements of the acoustic pressure of spark discharges were made at a shallow depth (10 feet) for various voltages, stored energies, inductances and capacitances of the system, and electrode areas. The voltages ranged from 1500 V to 11 KV, and the energy storing capacitances from 8 to 800 ufd. In this range the peak pressure observed was proportional to peak current and the decay constant of the pressure-time curve was essentially the same as the electrical discharge decay constant.

Description: Office of Naval Research under Contract Nonr 1 367(00) NR 261-103

Description: This progress report contains findings in 1) physical oceanography, 2) marine biology, 3) geology and geophysics, and 4) hydroacoustics. 1) Long-period internal waves are deduced from sound-velocity data between Bermuda and the Antilles . The region of the thermal front (usually found near 30°N) was thought on one occasion to be a generator of internal waves. 2) Midwater fishes were four times more abundant north of the front than south and midwater reverberation levels varied similarly. 3) Evidence obtained southeast of Charleston, S.C. shows that the continental shelf has been building out over the Blake Plateau. The gravity characteristics of many major rifts of the world reveal that as the width of the rift increases, the Bouguer anomalies become increasingly positive. 4) Observations support the hypothesis that diffraction effects are required to explain the sound propagation in convergence zones in the Mediterranean. A major engineering accomplishment was the installation and use of Sea Spider on the Blake Plateau. Sea Spider is a near motionless platform for scientific measurements in the deep ocean. The development of an automatic digital depth-reading system for use with echo sounders on ships were successfully completed, improvements in seismic profiling techniques were made, and special coherency studies of towed hydrophone array noise have progressed.

Description: Undersea Warfare Branch Office of Naval Re search under Contract Nonr-4029(00) NR 260-101

Description: In the fall of 1967 an extended program of tests was begun to evaluate several types of acoustic anchor release devices available on the market. This program was.prompted by a.need to isolate and correct problems which came to light after, several years of use of the O.R.E. system. Two other systems, one made by Raytheon and the other by American Machine and Foundry Co., were tested. This report deals with previous use of O.R.E.'s system by the W.H.O.I. Buoy Project and the testing program in 1968 and with the Raytheon and A.M.F. test series. Detailed description of these systems and their operation will not be undertaken in this report. Reference is made to data published by the respective manufacturers.

Description: Submitted to the Office of Naval Research under Contract N00014-66-C0241, NR 083-004.