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Summary PageThe ProblemTo improve the real-time auditory detection and aural analysis capability of passive broadband sonar systems. The FindingsThe most blatant source of acoustic signal degradation on auditory sonar systems is in the acoustic performance of headsets. Recent detection performance data have shown the need for upgrading sonar headsets to reproduce electrical energy accurately over a wider bandwidth. Headphone measurement data on commercially available headphones have shown that headphones of more appropriate bandwidth and frequency-response accuracy have not been of sealedcircumaural design. Headphones designed to completely seal around the listener's ear exhibit low-finequency variations with placement on the head and with deterioration of ear-cushion as a result of a less than perfect seal. Unfortunately, current noise levels preclude use of the more accurate, less variable, open-air types. Reduction of noise levels in sonar spaces to permit use of better headphone designs is a highly desu^ble solution. Recent developments in active noise canceling headsets show promise as an interim solution. A commercial model having adequately flat frequency response has been found and improved through active equalization. A prototype version of this improved headset has been evaluated. ApplicationAdvanced auditory sonar system design. Aural analysis and tactical sonar headphone requirements.Administrative Information This research was carried out under Naval Medical Research and Development Command Work Unit 65856N-M0100.(X)1-5001. It was approved for publication on 27 Jun 95, and designated as NSMRL Report 1197. u Abstract Real-time auditory detection and aural analysis capability of passive broadband sonar systems needs improvement. A weak link in these systems is the use of communicationsbandwidth low-fidelity headsets. Unfortunately, no procedure for headphone (earphone element inside headshell) frequency response measurement exists in military headset specifications. An accurate technique for headphone calibration was devised which provides the earphone element with an acoustic load similar to the one provided by a human wearer. Using this technique, headphone measurement data on commercially available headphones was collected and compared to the current sonar headsets. The advantages and disadvantages of open and sealed circumaural headsets and recent developments in noise canceling headsets are discussed, along with the possibility of reducing noise levels in sonar spaces to permit use of higher fidelity headphone designs.

Theoretical speculations concerning the presence or absence of intermanual transfer under differing conditions of sensorimotor adaptation have assumed that the adaptation produced by them are essentially equivalent. The possibility remains that sensorimotor changes generated by these different exposure conditions may be dissimilar. In order to resolve this, it is necessary to obtain relevant information from exposure conditions that provide adequate controls. Auditory rearrangement produced by functional rotation of the interaural axis by pseudophones (a binaural microphone/earphone array worn on the head), represents an exposure condition with suitable controls. Intermanual transfer of adaptation to rearranged ear-hand coordination produced after exposure to a 30° shift of the interaural axis was therefore investigated. FINDINGS Except for one exposure condition, changes in ear-hand coordination that occur to compensate the distortion induced by the pseudophones, fail to transfer intermanually. Such results suggest a differential representation of the sensorimotor function between the hemispheres. APPLICATION These findings are useful in design of auditory passive detection systems employing auditory tracking. They are for use of systems designers and human factors applications where sensorimotor tasks under conditions of perceptual rearrangement are anticipated. This information is of definite value to Naval medical officers in ear, nose, and throat specialities, and to audiologists.

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In a black-white successive discrimination, rats received a large reward (500 mg) in one alley, and a smaller reward (250 mg) in an alley of a different brightness. Results indicated nondifferential responding in the start segment, but superior performance to the stimulus associated with the smaller reward in the running and goal measures.Numerous investigations (e .g., Bower ,1961;Goldstein & Spence, 1963;Porter, 1964;Ludvigson & Gay, 1966) have shown that rats can readily learn to respond "appropriately" in a successive discrimination based on different reward magnitudes. Moreover, with the exception of the experiment by Goldstein & Spence (1963), these studies clearly indicate that performance to a given reward magnitude is influenced by the reward associated with the comparison discriminandum.In a recent magnitude discrimination experiment (MacKinnon, 1967), performance to one stimulus (81) was examined as a function of the reward magnitude coupled with the other stimulus (~) in the discrimination. 81:~ reward magnitudes (in mg) were500:500, 500:250, 500:90, 500:37, 500:0. The results clearly supported a "reward context" interpretation. That is, performance to ~ was not independent of the reward magnitude associated with 82' Of particular interest was the overall runway performance of 8s in the 500:250 group. Although start speed curves indicated only a slight tendency towards "appropriate" differential responding, there was a significant performance superiority to the small reward stimulus in the final two runway segments (running and goal measures).The present study constitutes a replication of the 500:250 condition in the MacKinnon (1967) experiment and was designed to further investigate this paradoxical finding of higher running and goal speeds to the stimulus signalling lesser reward. Subjects Ss were 10 naive, male albino rats of the Wistar strain, approximately 110 days old at the start of the experiment. ApparatusThe apparatus consisted of two parallel straight alleys, one of which was painted flat black and the other flat white. A Sliding, neutral gray, prestart box (PSB) and start box (SB) section could be moved into alignment with either alley. The PSB (11 in.) and SB (10-1/2 in.) were separated by a gray metal guillotine-type door. the SB from the alley proper. The length of each alley, from start door to food cup, located on the end wall of the goal box (GB). was 39 in. The length of the GB section was 13 in. Inside dimensions of each alley were 3-3/4 in. x 3 in. Response times, over three successive I-ft. segments of the alley, were recorded by means of 1/100 sec. clocks activated by a photoelectric system. Procedure 8s were maintained on a 23-hr. deprivation schedule for a 20-day period prior to the beginning of training. The Ss received a daily ration of 10 gm Purina checkers, which during the experiment proper, included the weight of pellets given as reward.DifferentIal magnitude discrimination training involved 144 trials (72 trials to each alley brightness). The reward magnitude associate...

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) 23-10-20012. REPORT TYPE technical 3. DATES COVERED (From -To) SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)Naval Submarine Medical Resea NSMRL rch Laboratory Naval Submarine Base New SPONSOR/MONITOR'S REPORTGroton, CT 06349-5900 NUMBER(S) 1221 DISTRIBUTION / AVAILABILITY STATEMENT AApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTESThis investigation was conducted for NAVSEA PMS 450T2 under Naval Sea Systems Command Task Statement 64559.50006. ABSTRACTThe current research evaluated various headsets for use on C3I (Command, Control, Communication and Intelligence workstation) consoles installed in Virginia Class submarine. Of particular importance is their intended application in accurately presenting not only communications but also passive acoustic sonar data and other future advanced auditory displays that may use spatial coding. Of these applications accurate representation of broadband sonar data be-comes the most challenging immediate task.Headset evaluation of commercial off-the-shelf products confirmed our decision to press for development of high fidelity ANC sensor operator headsets. This study reports evaluation of a prototype ANC high fidelity headset developed to our specification for use in critical listening in a moderately noisy environment. With renewed interest in presenting relevant acoustic information to the 3CI (Command, Control Communication and Intelligence workstation console) sensor operator including the broadband-search sonar operator, headset selection continues to present a problem due to the degree of noise in the room and its spectral content. FindingsConventional noise-occluding (closed shell) headsets were designed for communication and are appropriately band-limited in frequency response to optimize speech intelligibility. Closed-shell earpieces confound accurate sound reproduction due to cavity resonance and interaction between frequency response and seal against the head. High-fidelity headsets, which extend frequency-response accuracy to well beyond the speech range, avoid using nois...

The extent to which simultaneous inputs in a three-dimensional (3D) auditory display mask one another was studied in a simulated sonar task. The minimum signal-to-noise ratio (SNR) required to detect an amplitude-modulated 500-Hz tone in a background of broadband noise was measured using a loudspeaker array in a free field. Three aspects of the 3D array were varied: angular separation of the sources, degree of correlation of the background noises, and listener head movement. Masking was substantially reduced when the sources were uncorrelated. The SNR needed for detection decreased with source separation, and the rate of decrease was significantly greater with uncorrelated sources than with partially or fully correlated sources. Head movement had no effect on the SNR required for detection. Implications for the design and application of 3D auditory displays are discussed.