bluuebunny/crossref_metadata_2025 huggingface dataset:
Description of the Acoustical Laboratory at the University of California, Berkeley
Authors: Wilson George P.
Published: September 2005

The laboratory facilities are described from a design, construction, and acoustical point of view. The main part of this teaching and research facility consists of two reinforced-concrete reverberation rooms, located side by side. Details of the isolation against airborne noise and mechanical vibration are presented, along with discussion of the geometry of the rooms and the opening between the rooms. The interior-wall treatment resulted in reverberation times in excess of 10 sec; this treatment is described in detail. Results obtained for the upper limit of sound-transmission-loss measurements, ambient-noise levels, and reverberation times are presented. The instrumentation and methods used in the measurements are discussed.
Measurements of Noise Damage to Community Buildings near Launch Sites
Authors: Peverley Richard W.
Published: September 2005

An experimental study was initiated to determine damage thresholds of community buildings exposed to intense low-frequency rocket-engine noise. Acoustic tests were conducted on abandoned stores and homes at the John F. Kennedy Space Center. Fifteen buildings were exposed to sinusoidal sound-pressure levels of 135 dB in a frequency range of 20–600 cps. A series of laboratory tests was also conducted on a wall panel, using both sinusoidal and random noise. Five window panels were tested to destruction. Acceleration and strain data were acquired from window and wall panels during all of the tests. Thus, it was possible to determine acceleration response, stress response, and fragility levels. Data from other sources were combined with data from this program, and a generalized damage criteria was formulated. A survey was made to evaluate a cross section of a number of buildings in communities near the Kennedy Space Center. Structures were divided into categories according to materials, type of construction, etc. Thus, it was possible to compare the generalized damage criteria with predicted booster-engine noise levels to assess the noise damage probability. Test data and analysis techniques are presented and problems associated with developing community rocket-engine noise-damage criteria discussed. [Work supported by the John F. Kennedy Space Center, National Aeronautics and Space Administration.]
Hydroelastic Effects in Ship Slamming
Authors: Meyerhoff W. Kay
Published: September 2005

A theoretical investigation is presented on hydroelastic effects during the hydrodynamic impact of an idealized structure model of a ship. This is a summary of the author's paper, that will be published soon in Schiffstechnik. Based on H. Wagner's theory of hydrodynamic impact, the equations are formulated for the impact, including elastic deformations of the structure and their influence on the pressure field. This formulation holds for the 2-dimensional, vertical, symmetric impact of a structural model of small but nonzero deadrise angle. Compressibility effects are neglected. The general equations are then specified and evaluated numerically for a certain type of model. A normal-mode series expansion is used to calculate the motions of the bottom plates loaded by transient hydrodynamic pressures. The normal modes are those of the plates in vacuum. In order to obtain the pressures. the influence of deformations as well as of velocities and accelerations is considered. The pressures are obtained from a Fourier series involving Chebyshev polynomials. Special attention is given to convergence criteria of both series expansions. The original paper contains numerical results for five parameter combinations. Principal results of one of these examples are discussed.
Bearing Stability in an Ocean Medium
Authors: Nielsen R. J. , Karamargin M. C.
Published: September 2005

An experiment designed to study the effect that an ocean medium has on determining bearing of a sound source was conducted in deep water off Bermuda in the fall of 1964. The source was at a depth of about 1800 ft and two closely spaced receivers at about 12 000-ft depth and 12-mile range from the source were utilized. The experimental method employed a phase-comparison techniques on the output of the two receivers, and the parameters studied were pulse length, power level, and direct versus surface-reflected path. Experimental values of bearing error for different signal to noise were obtained and comparison with theoretical values was shown to be good. A noticeable bearing shift for signals that traveled via surface-reflected path was observed in comparison to the bearing of the direct-path arrival. A linear change of varying magnitude in absolute bearing with time was also observed over the length of the received signal at all signal-to-noise ratios. These latter effects are believed to be peculiar to the particular 12-mile path employed and were experimentally shown to be independent of the measuring system.
Caustics and Convergence Zones in Deep-Water Sound Transmission
Authors: Urick R. J.
Published: September 2005

The existence of convergence zones when both source and receiver are at a shallow depth is now a well-known feature of deep-water sound propagation. For other depth combinations, however, deep-sea convergence is not as well known. In this paper, ray diagrams and field data show that the single convergence zone observed, when both source and receiver lie within a few hundred feet of the surface, splits into two half-zones that migrate in range in opposite directions as the depth is increased. The behavior of deep convergence zones and their accompanying caustics is shown by ray diagrams and by confirming field measurements, using explosive charges dropped from an aircraft and a hydrophone at nominal depths of 3000, 6000, and 9000 ft. The convergence half-zones are found to have a convergence gain over spherical spreading of 5–10 dB and a zone width of 3–5 miles. The findings suggest that any point in the deep sea can be reached, acoustically, via a favorable convergence-zone path from any range by means of an appropriate selection of source or receiver depth.
Reproducibility of Reflections from the Bottom of the Ocean
Authors: Clay C. S. , Liang W. L.
Published: September 2005

The signals reflected by the bottom of the ocean are complex and dependent upon the location. Seismic-profiling data were taken in typically smooth and rough areas. The similarity of reflection signals as a function of the ship's position was studied for the areas. A portion of the reflection signal for a transmission was stored in a Deltic memory. The crosscorrelation of reflection signals from subsequent transmissions and the stored signal were measured. In smooth areas, the correlation of subsequent transmissions with the reference were about the same as the autocorrelation for over 0.5-nm translations. In rough areas, the correlations of the reference and subsequent transmissions were very small. [Hudson Laboratories of Columbia University Informal Documentation No. 66. This work was supported by the U. S. Office of Naval Research.]
Detailed Study of Sound Reflection from a Layered Ocean Bottom
Authors: Stangerup Paul
Published: September 2005

The effect of layered sediments on sound reflection from the ocean bottom has been investigated theoretically and experimentally. Very detailed systematic and computer-aided calculations of the reflection coefficient of a 2-layer bottom were made, using well-known theory and varying the following parameters: (1) velocity and density contrasts; (2) layer thickness normalized with respect to wavelength; (3) absorption in the sediments (in dB/wavelength); (4) shear-wave velocity in the lower layer. Calculations were made both for a harmonic source and for a broad-band source analyzed within certain bands around the harmonic-source frequency. A series of curves was obtained representing the 2-layer effect for a range of parameters that encompasses typical ocean-bottom values. It is shown that absorption in the upper layer is of great importance in sound reflection, especially beyond a critical angle, but that moderate shear-wave velocities have little effect. An octave-band analysis of experimental data—using a broad-band source—tends to support this theoretical 2-layer model.
Improved Pitch Perception with Training on a Single Tone
Authors: Cuddy Lola Lane
Published: September 2005

The present investigation was concerned with whether pitch judgment could be improved through practice. A preliminary study revealed that S's with training in music could judge pitches more accurately (with smaller average error) than subjects with little or no training. If S was a pianist, he named piano tones more accurately than pure tones. It appeared that pitch judgment was related to familiarity with musical tones. Music students who did not possess “absolute pitch” were given systematic training with a pure tone. The essential feature of the method was concentration on identifying a single reference standard—A4 (440 cps). Although other tones were presented, S was required to recognize only A4. 5 sec after each A4 was presented, a light signal came on and remained on while A4 was repeated. Experiment I showed that with practice S's improved their ability to recognize A4 in a random series of tones. Experiment II showed that, following this training, performance on a test in which 10 tones were named had improved significantly over ability prior to training. By comparison, training in which S is required to name each tone and is immediately told the correct response to each was not found to be effective.
Precision of Lateralization Using a Sequential-Estimation Procedure
Authors: Levitt H.
Published: September 2005

The precision with which a listener can lateralize a binaural-sound image about his medial plane was measured using three separate techniques, the method of constant stimuli, Mood and Dixon's up-and-down method, and a new sequential procedure (Wetherill's UDTR method). The latter technique was found to have several important advantages over the other two. An application of the UDTR method is described, in which the precision of lateralization for one of two mutually interfering speech sources was measured.
Response Latency as a Criterion-Dependent Measure
Authors: Watson Charles S.
Published: September 2005

The latency of responses to auditory stimuli is proposed to be a joint function of the time required to process sensory (auditory) information and of a criterion adopted by the listener. This criterion appears to represent a compromise between accuracy and a speed of responding that is adjusted to meet the demands of a particular listening situation. Evidence is presented that listeners can vary their accuracy in a binary-decision. single-interval detection task between nearly perfect and nearly chance performance, as instructions emphasize the relative desirability of accuracy or speed, with correspondingly large changes in response latencies. The “latency criterian” is discussed in relation to (1) latency as a measure of detectability, (2) latency in complex reactions (those requiring decisions about the stimulus), and (3) latency in simple reactions (those requiring no differential responses). [Work suported under a grant from the National Aeronautics and Space Administration through the U. S. Office of Naval Research.]
Effect of Repeated Practice with and without Feedback upon Discrimination Performance
Authors: Elliott D. N. , Riach W. D.
Published: September 2005

The effectiveness of feedback and repeated practice in improving simple auditory discrimination performance was investigated, using S's covering a wide range of initial discrimination performance. As to be expected, repeated practice resulted in greater improvement for S's initially performing most poorly. However, feedback was found to have little, if any, effect in speeding up the learning process. The significance of this is considered in terms of the temporal location of the feedback and the uniqueness of the discrimination task. [Research supported by the National Institute of Neurological Diseases and Blindness, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Frequency Discrimination following Auditory Fatigue
Authors: Brandt John F.
Published: September 2005

Threshold measures and frequency jnd's at 1000, 2000, and 4000 cps were obtained before and after fatigue by wide-band noise. Two test-stimulus SPL's were used during the postfatigue discrimination measures such that stimuli were presented at 10 or 40 dB SL re TTS3. The SPL remained constant throughout recovery during each experimental session. When test stimuli were equated in terms of SL, no differences between pre- and post-fatigue jnd's were noted at 40 dB SL or greater at any frequency. At low-stimulus SL's (10–20 dB), however, a differential effect on the jnd occurred owing to fatiguing stimulation that was not explainable in terms of TTS. At 4000 cps (maximum TTS), there was little discrepancy betwen pre- and post-fatigue jnd's. At 2000 cps, about 10% impairment in the jnd due to fatigue existed in the latter stages of recovery. At 1000 cps (no TTS), the postfatigue jnd's were about 40% greater than prefatigue jnd's and independent of recovery time. A paradox thus exists at low SL's between amount of threshold shift and frequency discrimination. [These data are based on a portion of a Ph.D. thesis completed at the University of Iowa under the direction of Prof. Arnold M. Small, Jr.]
Disruption of Microorganisms by Ultrasound—A Cooling Device for Use with the Sonifier
Authors: Rosett Theodore
Published: September 2005

The development of efficient high-powered ultrasonic transducers has rendered the disruption of microorganisms for the purposes of biological study a relatively easy task. However, high-intensity cavitation results in the generation of considerable heat, which is liable to denature the protein released from the cell. We have developed a simple cooling device that utilizes the cavitation pressure of the ultrasonic probe to circulate the cell suspension through cooling coils, and permits the maintenance of low temperatures even under high-intensity sonication. The efficiency of this device has been tested in conjunction with the Branson sonifier, by disrupting suspensions of S. cerevesiae, a microorganism that is resistant to disruption, and measuring the release of soluble protein, and of the enzymatic activity, yeast alcohol dehydrogenase. It was possible to completely disrupt a 10% wt/vol suspension of yeast in 10 min, while maintaining temperature of 0°–5°C and obtaining a very good yield of soluble protein and enzymatic activity. The methods used and the results obtained are discussed in detail.
Comparison of Vibration Potentials of Bovine Serum Albumin with That of a Paraffin Chain Salt
Authors: Beard Richard B.
Published: September 2005

Debye predicted that the propagation of ultrasonic waves produces periodic potential differences in ionic solutions and colloidal systems [Yeager et al., J. Acoust. Soc. Am. 25, 456–460 (1953)]. Vibration potential, viscosity, and conductivity data from bovine albumin have been compared with similar data on a micelle-forming paraffin-chain salt sodium lauryl sulphate (NaLS). NaLS in the critical micelle region is believed to form spherical aggregates. Vibration potential, viscosity, and conductivity curves have a marked change in slope in the critical micelle region. Similarities in the data from the two materials indicate that bovine albumin also may be experiencing a change in structure with change of concentration. [This work has been supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Experimental Investigation of Boundary-Layer-Induced Vibrations
Authors: McCormick Michael E. , Harrison Mark
Published: September 2005

Results of a recent experimental study of boundary-layer-induced vibrations of a thin metal ribbon are presented. These results were obtained by subjecting one side of a stainless-steel ribbon to a turbulent boundary layer in a subsonic wind tunnel. The displacements of the ribbon were measured with a capacitance probe. The coincidence effect that was encountered by R. H. Lyon in a similar study is observed in the present investigation. This coincidence effect occurs in the fifth mode of vibration when the free-stream velocity is approximately 1.2 times the wave velocity of the ribbon. This value of the velocity ratio differs from that observed by Lyon, which was approximately 0.85 for the fifth mode. It is believed that the coincidence effect occurs when the convection velocity equals the wave velocity. Following this line of reasoning, the present velocity ratio value of 1.2 is supported since the convection velocity has been found experimentally to be approximately 0.8 times the free-stream velocity.
Manned-Spacecraft Habitability Noise-Control Evaluation Study
Authors: Lepor Meyer
Published: September 2005

Control of acoustic noise is a serious problem in orbiting manned space vehicles. It has been established that the noise environment in a crewspace due to the operation of acoustically unabated equipment in addition to the excessive room reflections due to unattenuated normal modes of vibration are each expected to adversely affect the “shirt-sleeve” environment in terms of mission accomplishment and safety. It has been further established that acoustical materials in general use today cannot be considered for use in extended space missions contemplated due to their chemical nature as a source of contamination and toxicity. Significant progress has been made toward meeting the overall objectives of establishing acoustic design goals and noise-control design concepts for crewspace-habitability areas. The progress noted in this paper includes (1) the evaluation of toxicfree acoustical materials, (2) the development of engineering procedures for establishing acceptable noise-level criteria, (3) the development of engineering considerations pertaining to crew-station acoustics in terms of room-reverberation control, and (4) the application of materials, criteria, and crew-station acoustics in controlling the excessive-noise environment in a life support-system test bed.
Instrumenting to Identify Noise Sources in Document-Handling Machinery
Authors: Peterson Roger H.
Published: September 2005

One significant problem in machine-noise reduction is the quantitative evaluation of the noise sources. Plotting noise versus time is useful, but difficult at high cyclic rates. Response times of root mean square (rms) and objection-ability meters present major difficulties. An inverse approach has been taken to the problem. Instead of looking at the objectionability of the high cyclic noise occurring during a short time (Δt), the noise is attenuated during Δt, and the remaining signal is measured with conventional rms and objectionability meters. An electronic switch is controlled to switch a variable resistive attenuator into the microphone output during Δt. This switch, operating on a cyclic noise or a tape loop, attenuates the signal during Δt without changing the remaining signal. The switch is also used to simulate electronically machine improvements to study the acoustics without modeling. Plotting machine noise objectionability versus the cyclic time of the attenuated Δt offers a new and challenging approach to quantitative noise-source identification. Expansion of this technique has led to a noise rating (NR) meter system, which is now being evaluated.
Combinations of Channel Vocoders and Formant Vocoders
Authors: Gold Bernard
Published: September 2005

Channel vocoders and formant vocoders have both been used as speech-bandwidth-compression devices. Channel vocoders with 16 or more channels adequately recreate the synthetic-speech spectral envelope but fail to produce speechlike phase and are more wasteful of bandwidth than the formant vocoders. The latter, however, does not successfully synthesize all consonants. Computer simulation experiments have recently been carried out with several different configurations wherein elements of both formant and channel vocoders are combined. A 26-channel spectrally flattened channel vocoder excited by the output of a cascade-vowel synthesizer produced speech of excellent quality. An 8-channel vocoder excited by a vowel synthesizer produced speech of quality comparable to that of a 16-channel spectrally flattened vocoder. Improvements for the latter case were made by using a modified form of spectrum flattening and by adjusting the bandpass-filter bandwidths. The experiments indicate that the combinations of formant and channel vocoders can lead to systems that exploit the bandwidth-reduction and phase-enhancement properties of the former while maintaining the spectral definition of the latter. Demonstration tapes are played.
Novel Vocoder Synthesizer
Authors: Smith Caldwell P. , Helms S. W.
Published: September 2005

The design of speech-processing methods has proceeded under the assumption that a speech event can be represented by parameters that remain essentially constant during a single pitch epoch. A new method of synthesis is presented that closely approximates the actual modulation of both the resonant frequencies and their decrements, which occur systematically as fine structure superimposed on the formant frequencies within a single glottal epoch. This new approach to synthesis shows promise of better quality and intelligibility, as well as reduced weight, size, and cost.
Preference Scaling of Vocoder Speech
Authors: Mickunas J.
Published: September 2005

A study was performed to evaluate preferences for vocoder-processed speech. Tape recordings of conversational sentences were processed through five vocoders to provide stimulus materials. The method of pair comparisons was employed. Stimulus materials consisted of identical sentences. Each sentence was processed through a different vocoder. Distances between vocoders were calculated, using a more realistic statistical model that is different from those previously employed for purposes of evaluating communication systems. The arcsine transformation of observed preference percentages was used in conjunction with analysis of variance to derive scale values that more nearly satisfy the requirements of a psychological distance function. Data are presented for five vocoder designs. [The research reported in this paper was sponsored in part by the U. S. Air Force Cambridge Research Laboratories, Office of Aerospace Research.]
Communication-System Evaluation from the Standpoint of Speaker Recognizability
Authors: Voiers William D.
Published: September 2005

Procedures have been developed by means of which multidimensional voice-rating data can be analyzed to evaluate the capacity of a communications system for preceptually useful information as to speaker identity. In addition to a gross measure of capacity for speaker-identity information, these procedures yield measures of speaker-identity information transmitted via selected perceptual dimensions or perceived acoustic traits as well via various physical dimensions of the speech signal Results for representative designs and operating modes are described. [The research reported in this paper was sponsored in part by the U. S. Air Force Cambridge Research Laboratories, Office of Aerospace Research.]
Correlation of Subsonic, Audible, and Ultrasonic Recordings Cardiac Diagnosis
Authors: Kingsley B. , Segal B. L. , Likoff W.
Published: September 2005

Recording of heart sounds in the subsonic and audible frequency spectrum, motion of cardiac structures derived from ultrasonic echoing technique, as well as carotid pulse, are simultaneously taken to establish precise timing of the electromechanical intracardiac events and precise diagnosis of cardiac lesions. This is accomplished by the application of signature-analysis techniques already accepted through 25 years of experience in radar and sonar fields. These results are correlated with recent advances in the theory of cardiovascular sound transmission. The results of an integrated signature-analysis system defined as the visual, statistical, and numerical waveform analysis are presented from normal subjects and patients with valvular disease. The instrumentation, direct and photographic and magnetic-tape recordings are described, and each of the recordings is discussed. Particular emphasis is placed on the interpretation of ultrasonic echoes in patients with valvular disease, artificial valves, pericarditis, and hypertrophy of the cardiac chambers.
Effects of Calcium on Sound-Evoked Cochlear Potentials
Authors: Moscovitch David H. , Gannon R. Patrick
Published: September 2005

Scala tympani in guinea pigs were perfused with artificial perilymph solutions containing calcium in ionic concentrations from 2.7 to 80 mEq/L. Cochlear-potential responses to 7000-cps tone pips at 80 dB re 0.0002 dyn/cm2 were recorded from the first turn using differential electrodes. The cochlear-microphonic (CM) and negative summating-potential (SP) amplitudes recovered immediately following perfusion and were augmented relative to control values for several minutes thereafter. The N1 component of the action potential (AP) recovered within 2 min or less after perfusion with solutions containing normal concentrations of calcium, but was depressed for longer periods with increasing concentrations. Depression of the AP was qualitatively related to the increase in calcium concentration. Augmentation of the CM and SP and depression of the AP associated with increased calcium concentrations in scala tympani are discussed in relation to the generation of these potentials and the action of the olivo-cochlear bundle. [Work supported by Medical Research Council of Canada and Mona Bronfman Sheckman Fund.]
Psychological Pitch Scale: Use in Musical Composition
Authors: Pedersen Paul , Creelman C. Douglas
Published: September 2005

A subjective pitch scale, such as S. S. Stevens' mel scale, presents interesting possibilities for musical composition. In order to make the scale useful for composition, a computer analysis of the curve was made, which yielded a table of mels vs. frequency at 1-mel intervals. This scale, in which intervals of equal mel size are equal in subjective size throughout the audible frequency range, opens the way to some new concepts of melody and counterpoint. Possibilities for the use of the scale exist in composition for conventional instruments as well as in electronic music composition. A preliminary experiment was conducted comparing judgment of pitch intervals in the low- and high-frequency ranges of the scale with a standard interval in the 1000-cps range. Further experimentation is needed in several areas: (1) it seems probable that the extreme high-frequency range of the scale is not quite accurate; (2) the scale should be determined using complex tones; (3) the question of whether or not equal mel steps are equally discriminable needs clarification. Tape-recorded examples of the mel scale and its use in musical composition are presented.
50 Years of Physical Ultrasonics
Authors: Herzfeld Karl F.
Published: September 2005

The experimental investigations that first showed excess of sound absorption in gases above the classical value are described, and the theoretical ideas that lead to their explanation by relaxation processes are discussed. A survey is then given of later progress, which is closely connected with the rapid development of electronics, and of the parallel refinement of the theory. The work in liquids started somewhat later. The theoretical situation is more complex, but, for that very reason, ultrasonic measurements in liquids give information about problems absent in gases. The consideration of viscous liquids led to a connection with the behavior in glasses, in accordance with Simon's theory. In metals, the starting point, the methods, and the important frequency range for loss measurements were originally different; but here too the investigations and theoretical viewpoints have been multiplied and diversified.
Word Discrimination in Cat
Authors: Ruben Robert J. , Warfield Dickens , Glackin Robert
Published: September 2005

Ten cats, with one ear surgically destroyed, were trained to discriminate between the spoken words cat and bat. Pure-tone threshold were measured on 6 of these cats. Test trial were presented in which the words were distorted by chopping initial segments of varying durations. Similar tests were conducted with ten human listeners. The shortest chop duration at which discrimination was disrupted was very similar for the cats and the humans. The animals were subjected to intense broad-band noise for different time periods. They were retested on the word discrimination, the reaction to chopped words, and sensitivity to pure tones. Cochlear potentials and eighth-nerve action potentials were recorded and histological sections were made of the cochleas. The effect of the noise trauma on behavior ranged from no effect to apparent total deafness. Results were analyzed in terms of behavioral changes, cochlear physiology, and anatomical destruction of the cochlea.
Temporary Threshold Shifts in Monkey
Authors: Fujita Shiro , Elliott D. N.
Published: September 2005

Six squirrel monkeys were exposed repeatedly to a broad band of noise and TTS's then determined by behavioral testing at various frequencies. Exposure durations ranged from 5 min to 1 h, and TTS's were traced until recovery was complete or the shift was clearly permanent in nature. Data on the shape of the TTS audiograms are presented as is the relationship between size of initial TTS shift and time to recovery. Data are compared with those obtained by other investigators.
Reevaluation of the Effects of Competing Speech on Aided Discrimination of Monosyllables
Authors: Olsen Wayne O. , Tillman Tom W.
Published: September 2005

Earlier, Tillman and Carhart [J. Acoust. Soc. Am. 35, 1900(A) (1963)] reported data indicating that discriminatory efficiency of hypoacousic subjects decreased when they were forced to listen via a wearable hearing-aid system [J. Acoust. Soc. Am.]. Marked additional deterioration occurred when competing speech was introduced into the listening environment. In their experiment, the hearing aid was transformer-coupled to the high-impedance input of a speech audiometer, which delivered the signal to the hearing-aid receiver in the subject's ear. In the discussion following that paper, it was suggested that this method of terminating the electrical circuit of the aid may have produced extraneous distortion, which in turn led to poorer discriminatory performance than would otherwise have occurred. The present experiment employed the same hearing aid, speech materials, and hypoacousic subjects studied previously. This time, however, the aid was coupled directly to its receiver in the subject's ear. Although absolute scores changed somewhat, aided discrimination remained poorer than unaided, and the introduction of competing speech markedly increased this aided deficit. [This research supported by Veterans' Administration.]
Equivalent Forms in Intelligibility Testing—Limitations and an Alternative Procedure
Authors: Clarke Frank R.
Published: September 2005

There are several difficulties associated with construction and use of equivalent tests. Forms demonstrated to be equivalent under some conditions cannot be assumed equivalent under different environmental conditions. Forms are relatively fixed, and in lengthy testing programs the listeners' probability of a correct response may systematically change as he is repeatedly exposed to the same tests. Such drawbacks may affect the validity of an evaluation program. These disadvantages and others are avoided by use of tests whose items are randomly selected from a specified parent population. Usually, more items are required for this type of test to have the same precision of measurement as equivalent test forms. However, analysis of sources of variance in the two types of tests indicate that typically the randomly generated test forms need only be about 50% longer than perfectly equivalent tests in order to have equal or greater precision of measurement. Analysis is presented for free-response tests and for multiple-choice tests. Examples are given. [Work supported by U. S. Army Laboratories, Fort Monmouth, New Jersey.]
Speaker Identification by a Matching-from-Sample Technique
Authors: Carbonell Jaime R. , Stevens Kenneth N. , Williams Carl E. , Woods B.
Published: September 2005

This study examines the ability of observers to identify the speakers of short test utterance (monosyllabic words, spondee words, and phrases) when sample utterances by the speakers are available to the observers. In one series of experiments, utterances were presented aurally through headphones; in another series, the same utterances were presented visually as intensity-frequency-time patterns. The observer's task was to identify (or, in some experiments, to authenticate) the speaker of an utterance by making reference, as often as desired, to samples of that utterance by each of 8 known talkers, and to indicate the confidence of each judgment on a 4-point scale. Identification scores and confidence ratings were consistently higher for the aural than for the visual experiments. Error scores in the aural experiments seemed to be related to the phonetic content of the utterances. In the visual experiments, errors appeared to be dependent on both phonetic content and number of syllables. [Work supported by the U. S. Army Signal Corps; K. N. Stevens is also at the Massachusetts Institute of Technology, Cambridge, Massachusetts.]
Diagnostic Rhyme Test for the Evaluation of Communications Systems
Authors: Cohen Marion F. , Mickunas J. , Miller J. F. , Voiers William D.
Published: September 2005

A test for consonant articulation has been developed to provide a practical method of system evaluation with respect to 7 “articulatory dimensions.” It utilizes a pool of 128 rhyming-word pairs, each designed to test for the transmission of a specific feature. Either word of each pair may serve as the stimulus. The listener's task is simply to identify which member of the pair has been spoken. Any number of equivalent forms of the test may be generated by randomly varying the stimulus word. Successive administration of two or more equivalent forms is feasible as a means of obtaining any desired degree of score reliability. Four administrations can be accomplished in 10 min. With a crew of 8 listeners, the standard errors of the various scores are of the order of one percentage point over the range from 80%–100% articulation. In addition to a gross score for each feature, subscores for false alarms and detection failures are readily obtained.
Vibration Mounts for Nonrigid Structures
Authors: Ungar Eric E. , Dietrich Charles W.
Published: September 2005

In order to meet stringent high-frequency vibration-protection requirements, one generally must devise isolation systems that provide high attenuation at frequencies at which the items to be protected no longer behave like rigid masses. This paper reviews the shortcomings of classical, essentially springlike, vibration mounts for isolation of nonrigid structures, and discusses menus for obtaining better mounting systems. The effects of lumped-mass additions at the ends of the isolator are described for excitation sources of the velocity and force types. “Two-stage mounts,” consisting of a rigid mass between two springlike elements, are analyzed and shown to be particularly advantageous if the excitation source type is not fully known. Damping of the isolated structures in order to reduce their high mobilities at resonances is shown to increase the isolation effectiveness of the mounting systems. Performance data on practical two-stage mount installations are discussed.
Reduction of Ships' Noise by Viscoelastic Damping
Authors: James Robert R.
Published: September 2005

The need by the Navy for greater control of self and radiated ship noise has accelerated research and development of materials used for damping mechanical vibrations in ship's structures. Various materials such as treated felt, elastomeric compositions, epoxy formulations, and plastic compounds have been used with varying degrees of effectiveness as appended damping treatments. Currently, an epoxy formulation, developed by the U. S. Naval Applied Science Laboratory, and a plastic compound, based on a formulation developed by Monsanto Research Corporation under Navy contract, are being used on many shipboard applications. The latter compound consists of a plasticized copolymer of vinyl chloride and vinyl acetate filled with flake graphite. This compound constitutes a major advance in the development of damping materials. It has outstanding effectiveness at relatively low frequencies, and the compound can be modified easily to make it effective at specific frequencies and temperatures. The use of steel laminates in which the layers of steel are interleaved with layers of a viscoelastic damping material show considerable promise in applications where it is desirable for the structural member to have inherent damping capability. Such applications include machinery foundations and fairwater plates.
Propagation of Ionic Magnetohydrodynamic Waves
Authors: Sessler G. M.
Published: September 2005

Ion waves in a plasma, in the presence of a magnetic field, generally exhibit simultaneous transverse and longitudinal oscillations. The velocity of these “modified ion waves” depends primarily on the mass and temperature of the charged particles and on the direction and magnitude of the magnetic field. In a weakly ionized gas, the attenuation of these waves is mainly determined by the ion-neutral and electron-neutral collision frequencies. For a transverse magnetic field, wave propagation is only possible at frequencies larger than the geometric mean of the ion and electron cyclotron frequencies. Theoretical and experimental results on velocity and attenuation of ionic magnetohydrodynamic waves are described.
Air Waves from the Alaskan Earthquake of 28 March 1964
Authors: Young Jessie M. , Greene Gary E. , Goerke Vernon H.
Published: September 2005

It is shown that a complicated series of traveling atmospheric pressure waves recorded on microphone arrays at Washington, D. C., Boulder, Colorado, and Boston, Massachusetts, were produced by ground motion at the epicentral region, seismic surface-wave excitation at regions remote from the epicenter and the receivers, and by surface-wave radiation in the neighborhood of the receivers. Experimentally determined arrival directions, horizontal phase velocities, and acoustic and seismic travel velocities are used to infer regions of enhanced earth-atmosphere coupling near the Mississippi River delta and along the Rocky Mountains.
Radiation Pressure Calibration Using Torsion Balance and Spatial Integration
Authors: Sachs Thomas D.
Published: September 2005

A radiation pressure-calibration technique for probes using analog integration of the square of the pressure amplitude applied across the face of the absorber is reported. After discussion of the necessary system components and their interconnection, these elements are described. They include: a simple torsion balance capable of sensitivities of less than 110 dyn, and easily calibrated to better than 12%; a signal-evaluation system that takes into account field variations in amplitude, varying moment arms on the torsion balance, and integration limits on the face of the absorber. Indications are that probe-microphone calibrations with precisions of the order of a few percent in the megacycle/second region are feasible with this technique. [Work supported by the National Science Foundation.]
Pistonphone Calibration of Microphones at Infrasonic Frequencies
Authors: Dahlke H. E. , Van Houten John J.
Published: September 2005

The application and development of microphones for measurement of sonic-boom phenomena, studies involving atmospheric turbulence, and physiological investigations have placed increased emphasis on accurate calibration at infrasonic frequencies. To establish microphone response at extremely low frequencies with a very significant level of accuracy, investigations revealed that the pistonphone provided the only practical technique. The unit developed by our laboratory produces a sound-pressure level of 94 dB (re 0.0002 dyn/cm2) with a precision of ±0.2 dB at frequencies from 0.1 to 10 cps. At frequencies to 0.01 cps, heat conduction and potential air leakage reduce the confidence level in the measurement to ±0.5 dB. Further development work at low frequencies has been accomplished at sound-pressure levels approaching 180 dB. Other methods of microphone calibration have been investigated that may prove useful but do not compete with the pistonphone in terms of calibration accuracy.
Reverberation Measurements of Narrow-Band Noise Power in a Water Tank
Authors: Lubman David
Published: September 2005

Radiated noise power may be measured in reverberant water tanks by methods analogous to those used in air chambers. In underwater applications, narrow-band noise-power measurements are of particular interest but present a special problem because of difficulty in achieving adequate diffusion of the reverberant field. Consequently, a greater number of field points must be sampled to establish average energy density with good precision. The required number depends upon the statistical distribution of mean-squared pressure. This distribution was measured in a rectangular metal tank 1012×5×512 ft with noise bandwidth, center frequency, and tank absorption as parameters. One finding is that distribution variance diminishes as bandwidth increases toward a critical value. At greater bandwidths, variance is nearly unchanged. These results were applied in related experiments to measure power radiated by an LC32 hydrophone driven with narrow bands of noise. Measured power was used to predict freefield pressure, which was then measured for comparison purposes. [This work was sponsored by the U. S. Navy Bureau of Ships.]
Calibration and Analysis of Underwater Earphones by Loudness-Balance Method
Authors: Bauer B. B. , Torick E.
Published: September 2005

Recent experiments in underwater directional communication necessitated the use of earphones with uniform response characteristics. Two earphones from headset P-120-PQC-1 were calibrated underwater by loudness-balance method at 50 dB above 1000-cps threshold SPL. A 35-dB range in response was observed in a frequency interval of 200–4000 cps, with principal resonance at 600 cps. Equalization was provided, after considering the role of the 50-phon loudness contour, resulting in uniform response over the interval of 200–2500 cps. The experiment sheds some light on the role of aural vs bone-conduction modes in underwater listening and suggests some approaches to improved underwater earphone and calibration methods. [Work supported, in part, by U. S. Navy Mine Defense Laboratory.]
Dialects, Phonetic Transcriptions or Phonemes of English?
Authors: Bhimani B. V.
Published: September 2005

Let us define SmWn as a set of operationally defined homonyms of the word Wn the list Sm: one of the five lists studied. The set SHWn ≡∩m = 1m = 5SmWn contains homonyms of Wn in every one of these lists. Any word in SUWn ≡∪m = 1m = 5SmWn is a homonym of Wn, in at least one of these lists. (X)* indicates words not in X. A word in SPWn ≡ SUWn∩ (SHWn)* is a homonym of Wn in some list(s) but not in all lists. For a word Wn1 in Sg ≡ SmWn1⊂SUWn1, i.e., SPWn1≠Φ, the set Q = SPWn1∩ (SPWn1∩Sg)* primarily contains minimal pairs of words in Sg or in SPWn1 that are suitable for definition of phonemes according to Sm. Any word in Q is also a homonym of Wn1εSg according to at least one word list. The sum of all words that can be either homonyms or minimal pairs exceeds 37% of the above mentioned homonyms: a measure of the differences in dialects, or of imprecisions of phonetic transcriptions, or of requirements in phoneme definition? [Work supported by Lockheed Independent Research.]
Technique for the Representation of Speech Power-Spectrum Envelopes
Authors: Carbonell Jaime R. , Grignetti M. C.
Published: September 2005

It is usual to plot the short-term speech power-spectrum envelope using nonlinear coordinates such as level vs log frequency, or other coordinates related to the way that a signal is perceived. The technique presented here involves the expansion of the spectrum envelope (described by nonlinear coordinates) in terms of a set of convenient orthonormal functions. The method is, related, but not identical, to the one employed by Pirogov in the harmonic vocoder and Schroeder in the autocorrelation vocoder. It can be conveniently incorporated in present speech-compression and -recognition systems. Results of a preliminary computer simulation are presented. Fourier series expansions were tried, but other orthonormal expansions, such as Laguerre and Tchebicheff polynomials, and orthonormal exponentials are also appropriate.
Mathematical Formulation of a Class of Acoustic-Radiation Problems Involving Line Sources
Authors: Cretella J. P. , Spence J. E.
Published: September 2005

In the analysis of many acoustic wave-propagation problems involving sources in an environment of layered media, one is posed with the task of evaluating Fourier-type integrals whose kernels involve more than one pair of branch points and a finite number of poles. Since exact representations for these integrals are not easily obtained, the usual procedure is to employ the saddle-point method, which furnishes asymptotic expansions that are valid only in the far field. In addition, the useful domain of these expansions does not include the region about the shadow boundary associated with the surface-wave modes. In this paper, we present a procedure that yields representations that are valid from the near to the far field; our expressions are particularly useful in the vicinity of the surface-wave shadow boundary. Typical problems to which our procedure can be applied include an acoustic line source above a liquid-liquid or liquid-solid interface and an acoustic line source within a liquid layer above a stratified solid substrate.
Reciprocity Relations for Radiation and Diffraction in a Moving Medium
Authors: Newman J. N.
Published: September 2005

Reciprocity or symmetry relations, based upon Greens' theorem, can be used to relate different components of unsteady pressure forces acting on bodies. Relations of this type have been derived in linearized acoustics, and a particularly useful result is the fact that the scattering force exciting any given vibration mode of a body in an incident-wave system can be found from the radiation characteristics of the same body performing forced vibrations in the same mode. In this paper, these relations are shown to be valid in a moving medium as well, thus providing symmetry relations for the matrix of pressure forces associated with forced vibrations in different modes, and also providing a relation between the scattering forces and the corresponding modes of radiation. The principal effect of the moving medium is to require that the direction of steady motion be reversed in the two complimentary forces or modes. In this respect, the results are analogous to the “reverse-flow” theorems of aerodynamics.
Underwater Radiation from a Finite Homogeneous Cylindrical Shell
Authors: Smith P. W. , Kerwin Edward M.
Published: September 2005

Analytical predictive techniques recently tested for shells in air [J. Acoust. Soc. Am. 36, 1691–1698 (1964)] are adapted to shell vibrations in a liquid. The large characteristic impedance of the fluid accentuates some new features. The set of shell modes is divided into broad categories according to both impedance and coupling properties. Some major features: Many lobar modes are highly resonant but are poor radiators for reasonable amounts of internal damping. Large-scale modes are radiation-resistance-limited and are good radiators over broad frequency ranges. Edge modes are moderately resonant (damping probably controlled by radiation) and are especially numerous near the ring frequency. [Study supported in part by U. S. Office of Naval Research.]