bluuebunny/crossref_metadata_2025 huggingface dataset:
Binaural Listening and Interaural Noise Correlation
Authors: Trittipoe William , Pollack Irwin
Published: September 2005

Six initially naive listeners attempted to detect the absence or presence of a 180° change in phase of a white noise voltage at one of two matched binaural earphones. Over the range of conditions examined, duration (range: 10 to 1000 msec) and frequency band (low pass to 200 cps and high pass to 4000 cps) modified phase detection performance substantially less than noise level (30 to 90 db SPL). The role of interaural noise correlation was examined with 6–8 experienced listeners. Following the procedure of Licklider, a common noise source (C) was mixed individually with two independent noise sources (A and B) and presented to separate earphones. The largest interaural noise correlation discriminable from perfect correlation was determined by presenting (C+B) to one earphone, and either (C+A) or (C+B) to the other earphone. The 75% recognition differential was obtained with a C/(A or B) ratio of +12.0 db, which is equivalent to an interaural correlation of about 0.97. The minimal interaural noise correlation for detection of a 180° change in phase was determined by presenting (C+A) to one earphone, and (C+B) was presented either in phase or 180° out of phase to the other earphone. The 75% recognition differential was obtained with a C/(A or B) ratio of −1.0 db, which is equivalent to an interaural correlation of about 0.66.
Loudness Judgments on Clicks
Authors: Geisler C. D. , Molnar C. M. , Peake W. T. , Weiss T. F. , Sandel T. T.
Published: September 2005

Two groups of experiments were performed to study the ways in which listeners will scale and categorize acoustic clicks of different intensities. The first group of experiments posed to listeners the task of estimating the numerical magnitude of clicks that varied in intensity over an 80-db range. In one experiment a standard click was presented 10 times at the beginning of each test series (81 clicks), in another experiment a standard click was presented before each stimulus, and in a third experiment no standard click was given. In a second series of experiments, the listeners were asked to assign clicks according to their loudness to one of five categories; the intensity ranges covered and the number of stimulus levels varied. The results of the magnitude estimation experiments agree reasonably well with the Stevens scale of loudness L = KI0.3; there is the usual amount of inter- and intra-listener variability. The results reflect to some extent the subjects' peculiarities in the use of numbers. The results of the categorization experiments demonstrate that the assignment of clicks to loudness categories depends not only on the intensity of the particular click which is being judged but also to some extent upon the stimulus ensemble as a whole. [This work was supported in part by the U. S. Army (Signal Corps), the U. S. Air Force (Office of Scientific Research, Air Research and Development Command) and the U. S. Navy (Office of Naval Research).]
Low-Frequency Sound Transmission in Very Shallow Water
Authors: Urick R. J. , Moore R. T.
Published: September 2005

As an aid toward understanding sound propagation in shallow water, transmission measurements were made in St. Andrew Bay in water between three and four feet deep, in which the geometry may be readily controlled and repeated without using ships. The measured transmission curves in the interval 100 to 3000 cps and over the range 1 to 200 yards were found to be represented by a two-parameter family of functions of the form Loss in db = 10n logr +αr, where n and α are spreading and absorption coefficients, respectively, and r is the distance between source and receiver. The parameter n was found to decrease with frequency from about four to about unity, with a value of two at the cutoff: frequency for first-mode transmission; a increases with frequency, presumably because of losses to the bottom. However, considerable deviations from a uniform behavior occur at individual frequencies, especially below 100 cps. These measurements in four feet of water agree well with older data in forty feet of water further out in the Bay when a scaling factor of 10:1 is applied to all distances and frequencies. This indicates that the structure of the bottom, which does not scale, plays little part in the transmission over the distances involved.
Sonic Depth Recording of Bubble Cluster Migration from Underwater Explosions
Authors: Nafe John E. , Tirey George B. , Ewing Maurice
Published: September 2005

Bubble clusters formed by underwater explosions have been tracked on the precision depth recorder of the research vessel VEMA. Observations were made with the ship hove to in quiet water of depth about 500 fathoms. Charges ranged in size from 3 to 55 lb of TNT and were exploded at depths between 100 and 250 fathoms. The bubble clusters were observed for periods as long as nine minutes during which the recorded trace indicated a 300-ft rise of the cluster.
Formant Tracking by Computer
Authors: Bell C. G. , Poza F. , Stevens K. N.
Published: September 2005

At the last meeting of the Acoustical Society of America a method of formant tracking using a digital computer was described. By this method synthetic speech spectra, constructed within the computer from a catalog of elemental spectra, are compared with measured spectra of a speech signal. The present paper discusses the evaluation, extension, and refinement of this method of analysis. Computer techniques which result in the display of a “synthetic sonagram” are described, together with examples of the use of the computer oscilloscope for displaying intermediate steps in the spectral matching process. Results obtained with a variety of speakers are presented. The problems of preparing a representative catalog of glottal spectra, evaluating the role of analyzing filter banks, and determining a meaningful “fit criterion” are considered. A method similar to the foregoing for synthesizing fricative spectra is also described. [[This work was supported in part by the U. S. Army (Signal Corps), the U. S. Air Force (Office of Scientific Research, Air Research and Development Command), and the U. S. Navy (Office of Naval Research); in part by Air Force Cambridge Research Center Contract AF 19(604)-2061; and in part by the National Science Foundation.]
Mathematical Theory of Woodwind Fingerholes
Authors: Benade A. H.
Published: September 2005

It has been shown on general grounds that there are only two types of bore that are suitable for use in woodwinds: the cylinder and the cone. Elementary consideration of the effect of closed side holes showed that their sizes must be graduated along the bore if its special properties are to be preserved [A. H. Benade, J. Acoust. Soc. Am. 31, 137–146 (1959)]. Further work will be described showing that although woodwind side holes are not evenly sized or spaced, lumped-constant transmission line theory can be applied. Equations for the frequency dependent “length corrections” for a bore with some open and some closed holes are obtained. The formulation implies several ways of dealing with the intonation problems of woodwinds, and explains the effect of side holes on timbre. The function of the bell is clarified, and the radiation pattern from the holes is deduced. It is shown that there is a unified design procedure for bores, holes, and bells, which can be based if desired on the “best” notes of an existing instrument. Experimental evidence will be presented in support of the theory.
Further Assessment of the Effects of Intensity upon the Pitch of Pure Tones
Authors: Cohen Alexander , Corso John F.
Published: September 2005

Typical methods for observing the effects of intensity upon the pitch of pure tones involve varying the frequency of one tone of fixed intensity (the comparison tone) so as to match the pitch of a second tone of fixed frequency (the tone under test) as the latter is set at different intensities. Differences between the frequency of the comparison and test-tones, when equated in pitch under these conditions, are attributed to their differences in intensity. These differences are used as a measure of the intensity induced pitch shift for the test tone. The comparison and test tones may differ in frequency, however, even when both tones are equated in pitch under equal intensity conditions. These frequency differences, reflective of pitch matching errors, conceivably may vary for different frequencies and intensities so as to nullify apparent pitch-intensity shifts or qualify the magnitude of those being observed. This possibility was studied in two experiments which were intended to reproduce Stevens' pitch-intensity relationship as well as explore new functions for tones of particularly low frequency, It was found that half of the “pitch-intensity” shifts noted for frequencies 50, 75, 100, 150, 200, 400, 700, 1500, and 6000 cps were not significantly different from pitch matching errors. The remaining shifts were in directions reported by Stevens but were typically small (2% or less). The lowest frequency tone to show a significant pitch change was 75 cps.
Pitch Discrimination of Complex Sounds
Authors: David E. E. , Schodder G. R.
Published: September 2005

Apparently the pitch limen for a single, high-frequency sinusoid can be smaller in the presence of a nearby constant frequency component than in isolation. The explanation lies in the time-envelope properties of the two-frequency complex. This reduced DL is considerably larger in cps but smaller in percentage than the DL for a sinusoid of the envelope frequency. This fact is a possible explanation of the results of Flanagan and Saslow who found that the pitch DL of a periodic vowel sound is smaller than the DL of sinusoids at the fundamental frequency.
A New Pitch Scale
Authors: Harris J. Donald
Published: September 2005

The mel scale derived by Stevens and associates has proved extremely useful as an explanatory concept in communications, frequency filtering, and critical band theory. Undoubtedly there exists a need for some such scale, but attempts to reproduce the mel scale have generally foundered on individual differences. Fractionation of frequency does not lend itself readily to standardization. Several years experience has convinced the writer that fractionation of frequency is possible for persons without absolute pitch, but that pitch scales among individuals are so unlike that an “average” scale is not very convincing. Large and variable constant errors are introduced when grossly disparate frequency regions are presented for comparison judgments. A method was used presenting only relatively narrow frequency regions. Given A-B (musical intervals avoided) subject is asked to set a tone C such that B-C = A-B. Subject is then given B-C and asked to set D; and so on up and down the frequency scale. It can be shown that if A-B is wide enough, a mel scale similar to the usual fractionation scale is obtained for any individual; but a critical interval exists furnishing a relatively invariant mel scale which is not changed if the initial interval is made even narrower. Thus the error in the fractionation-mel scale is measured and a new scale furnished freed of this error and much more like among individuals.
Boundary Layer Induced Flow Noise
Authors: Dyer Ira
Published: September 2005

A discussion is given on the magnitude of flow noise in underwater devices associated with turbulent boundary layers. Measurements by Willmarth and Harrison of boundary layers in air are used to determine a phenomenological form for the boundary layer pressure field. In calculating the resulting noise, attention is restricted to geometries and conditions of interest in underwater devices. In essence the work is an extension and improvement of that presented previously (Dyer, Second Symposium on Naval Hydrodynamics). [Supported by the Office of Naval Research under Contract Nonr-2321(00), Task NR 062-205.]
Sound Radiation by a Turbulent Boundary Layer
Authors: Skudrzyk E. J. , Haddle G. P.
Published: September 2005

A turbulent boundary layer is a very inefficient sound radiator, but it does radiate sound. The theory for radiation from boundary layer turbulence is derived and is compared with experimental results.
Line Hydrophone with Frequency Dependent Beam Steering
Authors: Mechler M. V.
Published: September 2005

A five element line hydrophone will be described in which the acoustic axis of the transducer is steered as a function of frequency. The direction of the hydrophone's maximum response is altered by the introduction of incremental phase shifts in the output voltages of successive motor elements. The phase shifts are introduced through the action of an LC network which produces an approximately linear phase distribution over the length of the line. The slope of the linear phase distribution is a function of the difference between the frequency of the incoming signal and a center frequency which is characteristic of the network. When the incoming signal occurs at the center frequency of the network, no phase increments are introduced and the transducer's characteristics are quite similar to those of a simple line hydrophone. However, in a certain band about the center frequency, the slope of the phase distribution is roughly proportional to the deviation of the signal frequency from the network's center frequency. The hydrophone design was based on a prototype consisting of a multisection, constant k, bandpass network. The hydrophone elements are made up of BaTiO3 and are operated over a frequency band about mechanical resonance. (This work was partially supported by the Bureau of Ships.)
Effect of Phase Errors on the Direction Finding Precision of Hydrophone Arrays
Authors: Bell Thaddeus G.
Published: September 2005

The direction from which an underwater sound wave is traveling may be determined by a fixed hydrophone array and suitable time delay circuitry. One of the constraints on the precision with which the sound direction may be determined is the error in the phase of each hydrophone's electrical output as compared with the phase which would be obtained by perfectly located, uniform elements. Both location errors and nonuniformity of elements introduce the phase errors. In order to specify tolerances on phase, the system designer is interested in knowning quantitatively how these phase errors affect the indication of sound direction. This paper derives a theoretical relation between the statistics of phase errors and direction-finding errors. Experimental evidence is presented from measurements on the performance of two multi-element, scanning-sonar type circular arrays.
Handling, Visual Selection, and Analysis of Digital Data Using a Digital Computer
Authors: Peterson H. L.
Published: September 2005

Storing data from acoustical experiments so that they may be recovered or played back for precise laboratory selection and analysis has always been a difficult problem. A method is described in which a continuous signal is sampled, quantized, coded, and recorded on magnetic tape in the form of straight binary digital numbers of 10-bits plus sign. These numbers are then handled using digital techniques. The method uses a start-stop recorder, sequential core memory, digital computer, computer memory scanner, and a plotter. The core memory performs the buffering of data from the recorder to the computer memory. In operation the playback digital recorder fills the core buffer with a block of 100 words at some convenient rate and stops. The block of data is then transferred electrically from the core buffer to the computer memory at the synchronized word rate of the computer. To aid in data selection, a digital-to-analog converter and an oscilloscope display are used to permit scanning the data visually while in either the core memory or the computer memory. An associated plotter is used to plot out the original data and the results of analysis. All operations of external equipment are under the control of special commands stored in the computer memory as subroutines along with arithmetic processing routines. This arrangement allows the handling and the arithmetic programs to be intermixed in any combination of data selection and processing that is desired. An example of data selection and arithmetic analysis is described.
Review of Current European Research in Speech and Auditory Perception
Authors: David Edward E.
Published: September 2005

This paper describes some of the major European research efforts in the areas of speech and auditory perception. An evaluation is made of the status and objectives of the research, and the work is compared and related to similar undertakings in this country. Suggestions are made toward the application of existing and potential results to the transmission of speech information.
Combined Spectral and Temporal Segmentation of Speech
Authors: Brandauer Carl M. , Reilly Norman B. , Liberman A. M.
Published: September 2005

A series of perceptual experiments have been performed using real speech arbitrarily segmented in the frequency and time domains. Various combinations of temporal and spectral segmentation were used. Another variable investigated was the method of presenting the segmented speech to the listener. Some of the methods of presenting certain of the combinations of segmented speech yielded higher intelligibility scores than did other combinations with different methods of presentation. The relationship of these findings to simple band-width reduction schemes and auditory theory will be discussed. [This research was supported by the Department of Defense in connection with Contract DA 18-119-sc-260.]
Intense Sound Output of a Nickel Magnetostrictive Transducer
Authors: Whymark R. R.
Published: September 2005

The continuous acoustic power output of a water cooled magnetostrictor is measured calorimetrically by a continuous flow method in which the heat energy of the transducer is isolated from the acoustic load. Excitation and acoustic loading are adjusted for intense sound generation. An acoustic output intensity of 200 w/cm2 was recorded for a thin, laminated, nickel bar resonant longitudinally at 20 kc/sec. Measurements at larger sound intensities could not be obtained owing to internal heating of the magnetostrictor. However, the dynamic magnetostrictive stress is measured at saturation excitation by employing an acoustic load of known value that heavily loads the transducer. Calculations based on this stress value show that a “saturation” sound intensity of 2 kw/cm2 is attainable with a nickel magnetostrictor carefully matched to its acoustic load. Load variations are provided by tuned stubs coupled to an end face of the transducer by means of mechanical transformers of ratio appropriate to the desired load. An alternative method to determine sound intensity consisted in the direct measurement of vibratory displacements at the load structure; the sound output is deduced from the decrement of the load material. The results of the two methods agree within ±10% for all load values.
Acoustic Instrumentation for Measurements in the Minuteman Silo
Authors: Kamperman G. W. , Keast D. N.
Published: September 2005

An instrumentation system has been developed to measure, record, and analyze various properties of the dynamic pressure field in the Minuteman launching silo. This system permits the simultaneous recording of up to 13 channels of data from microphones placed in the silo environment. These data may then be subjected to spectrum analysis, time correlation analysis, or space correlation analysis. The system has a frequency response from 0 to 10 000 cps, a wide dynamic range, and (to permit correlation analyses) a maximum channel to channel phase difference of 10°. Various system design problems are discussed. These include the choice of transducers to function in the high temperature, high vibration environment of the silo; the equalization of phase shift between the data channels, and the phase matching of pairs of filters for space correlation. Representative samples of data obtained with the system are used for illustration. [This work was supported by the U. S. Air Force under Contract No. AF 04-(647)-316.]
Numerical Solution for the Problem of Long-Range Sound Propagation in Continuously Stratified Media, with Applications to the Deep Ocean
Authors: Tolstoy I. , May J.
Published: September 2005

Since the formal solution for guided waves excited by a point source in an arbitrarily stratified medium is well known, in the sense that it can be written down in terms of (unexplicited) eigenfunctions and their derivatives, it follows that evaluation of the long-range sound field becomes a purely computational problem once these eigenfunctions can be calculated. One of a number of possible methods is presented here. It consists of two steps. First, the continuous sound velocity function α(z) is approximated by a succession of layers such that α has the form (pz+q)−12 in each: the exact wave functions for a layer are then known (combinations of Bessel functions of order ±13). The second step, which puts this scheme within easy reach of moderately fast computers such as the IBM 650, consists in representing these wave functions by polynomials (argument of Bessel function ⩽2.5π) or by the first few terms of their asymptotic expansions (with better than six-figure accuracy in both cases). Accurate solutions are obtained in this manner without difficulty, for both strong or weak velocity gradients. Some typical results for a deep ocean are displayed. It is also shown that near field problems can be solved in the case of a source and receiver in, or near, a local velocity minimum or duct. (This work was supported by the Office of Naval Research.)
Fluctuations in Pulsed cw Transmission
Authors: Brown M. V. , Ricard J.
Published: September 2005

Pulsed cw signals were transmitted from an electromagnetic transducer situated in the deep sound channel, and were received by a hydrophone at a similar depth, at ranges of from 1 to 6 kyd. A study of the fluctuations of ∫ P2dt has shown that for the sound channel arrival, the relative fluctuations increase with range. For ranges from 2 to 6 kyd, the relative fluctuation is approximately KR1.1. The surface reflected arrival has a maximum relative fluctuation at 1 kyd, a minimum relative fluctuation at 3.4 kyd, and increasing scatter out to the maximum range. Tentative explanations for these phenomena, justification for the relating of results using ∫ P2dt to those using Bmax, plus correlation with results published by other scientists will be discussed. (This work was supported by the Office of Naval Research.)
Absorption and Reflection Characteristics of a Water-Filled Anechoic Tank
Authors: Marboe Robert F. , Farwell Robert W.
Published: September 2005

Measurements made in the water-filled anechoic tank at the Ordnance Research Laboratory indicate that the lining of Insulkrete wedges absorbs more than 99% of the direct signal energy at frequencies between 30 and 105 kc. Between 20 and 30 kc the tank is better than 90% absorbent. The absorption falls off considerably below 20 kc. Comparisons of the reverberation and the reflection measurements in the unlined tank are included. At frequencies above 40 kc the apparent plane of reflection in the lined tank is at the tip of the wedges.
Minimum Audible Field of the Cat
Authors: Miller James D. , Watson Charles S.
Published: September 2005

In the course of our studies of persistent and temporary threshold shifts in the cat, audiograms have been obtained on a total of 39 monaural cats. These cats were trained and the thresholds were obtained by methods similar to those used in previous investigations. There is good agreement between our results and those from various laboratories, e.g., Neff and Hind [Acoust. Soc. Am. 27, 1955]. Intra-cat and inter-cat variabilities in thresholds will be presented for three modifications of the psychophysical method of limits. Details of the methods and their practicability will be discussed. [This research was supported by the U. S. Air Force under Contract No. AF 33(616)-3844, monitored by Aero Medical Laboratory, Directorate of Research, Wright Air Development Center, Wright-Patterson Air Force Base, Ohio.]
Aircraft Cabin Comfort Studies
Authors: Dreher John J.
Published: September 2005

Several psychophysical tests relating to aircraft cabin comfort studies are described and the results are discussed in relation to speech interference level (SIL) measures. Different conditions of subject motivation and attention are seen to affect the threshold annoyance level, with about 27 sones representing the “normal” operational threshold for both actual and synthetic spectra of propeller-driven aircraft type.
“Near Field” Study of a Jet-Engine Noise
Authors: Macpherson P. A. , Thrasher D. B.
Published: September 2005

A noise survey was carried out at various locations within twenty feet of a jet-engine, to determine the generated sound field. The instrumentation was such that it was possible to obtain a tape recording of the noise over a frequency range of 20–100 000 cps. The calibration of the high-frequency transducer resulted in a theoretical evaluation which indicated that the transducer should be insensitive to a discrete set of frequencies. The analysis of the recorded data indicated that it is possible to have sound pressure levels at high frequencies (10 000–100 000 cps) in excess of the over-all sound pressure level normally measured from 20 to 10 000 cps. (This is DRML Tech. Memo. No. 27-10; DRML Project No. 27; P.C.C. No. D50-95-13-04.)
Noise Field of a Large Rocket
Authors: Franken P. A. , Kamperman G. W.
Published: September 2005

The pressure field along a large liquid-propellant rocket engine has been measured during static test stand operations. Data were obtained over the frequency range of 2 cps to 10 000 cps. Amplitude and phase characteristics have been analyzed and cast in a general form. The results have been compared with data from other rockets and jet systems. [Supported by U. S. Army Contract No. DA-19-020-ORD-4685.]
Atmospheric Turbulence as a Flight Vehicle Noise Source
Authors: Franken Peter A.
Published: September 2005

When a vehicle such as a rocket moves through atmospheric turbulence of large spatial scale, the pressure is at any instant essentially uniform over the entire vehicle surface, but this uniform pressure changes randomly in time. Measurements of gust load spectra provide estimates of the significant parameters describing the pressure field. The modal response of a simple elastic system and the sound reradiated by this system are determined. Atmospheric turbulence appears to be a potentially significant noise source in flight vehicles. [Supported by Wright Air Development Center under Contract No. AF 33(616)-6217.]
Experimental Investigation of Cavity Collapse Pressures
Authors: Jones I. R. , Ellis A. T.
Published: September 2005

Single, hemispherical spark cavities were created in water at the pressure end of a Duralumin pressure bar. At the collapse of such a cavity, a transient stress pulse (∼20 μsec duration) is propagated along the bar which is detected by an X-cut circular disk of quartz of the same diameter as the pressure bar. The charge liberated at the surface of the crystal when the X-cut quartz disk is traversed by the stress pulse was converted into a voltage pulse which subsequently was amplified and recorded photographically from a cathode ray oscillograph. These photographic records yield only information regarding the total lifetime of the cavity and the maximum amplitude and time variation of the force developed during its collapse. However, an ultra-high speed photographic technique employed in conjunction with the piezoelectric pressure bar permits an estimate of the peak pressure developed at the site of collapse of the cavity to be made together with an observation of the time variation of the pressure within the cavity in the last stages of collapse. Cavities having maximum diameters of up to 12 in. have been studied during the course of these experiments and collapse pressures of at least 10 000 atmospheres have been observed.
Acoustic Spectrum of Transient Cavitation Processes
Authors: Zarwyn Berthold
Published: September 2005

Most of the studies of acoustic spectrum generated by the presence and collapse of bubbles are based on the steady state nucleation theory combined with the theory of the growth and collapse of a single bubble. Possible application of techniques based on the acoustic spectrum of collapsing bubbles are in the field of determining the temperature inside a nuclear reactor, the maneuvers and changes of speed of submerged bodies, etc. A method will be presented of extending the acoustical spectral analysis to the transient phenomena by considering the time dependent nucleation theory. It will be shown how this technique yields results which enable the detection of various parameters of the cavitating or nucleate boiling system which are not accessible by the present method, based on steady state nucleation processes.
Practical and Experimental Aspects of Cavitation
Authors: Karpovich John
Published: September 2005

Cavitation generators will be reviewed. The behavior of cavities and the consequence of such behavior will be discussed. A number of useful applications as well as undesirable effects of cavitation, will be presented and each will be associated with one or more of the consequences of cavitation. The scope and limitations of this form of energy will be covered.
Temporal Sampling Parameters of Interaural Correlation
Authors: Pollack Irwin
Published: September 2005

Does the auditory system extract binaural information better from a single package of information or from several shorter packets, distributed in time? Distribution of packets in time is apparently superior. The minimal interaural noise correlation that was discriminably different from a noise interaural correlation of zero was determined. Over a wide range of conditions, an “off” interval of about 2–5 msec between successive packets yielded optimal performance. The distributed condition apparently permits recovery of the auditory system between successive packets; whereas, more widely distributed packets apparently do not permit adequate short-time memory or integration of binaural information.
Binaural Interaction of Impulsive Stimuli and Pure Tones
Authors: Harris Gerard G.
Published: September 2005

An experiment in binaural lateralization was performed to measure the time intensity trade for pure tones and impulsive stimuli of varied frequency content. The intensity difference between the stimulus at each ear was set by the experimenter. The subject then varied the relative timing of the two stimuli and reversed the inputs to the ears until the fused image was in “null” position. This was done for all pass, high-pass, and low-pass clicks at a repetition rate of 20 pulses per second and pure tones at frequencies 200, 500, and 700 cps. Mean intensities of 20, 30, 40 db SL, and intensity differences of 0, 4, and 6 db were measured. The results indicate a difference between high and low frequencies. For instance, the first-order coefficient of the time vs intensity trade, a1, at 20 db SL varies from ∼0.100 msec per db when frequencies above 3000 cps are present, to ∼0.030 msec/db when only frequencies below 1000 cps are present. The values of a1 for pure tones are similar to those of low-pass clicks with frequency cutoffs equal to the frequency of the pure tones.
Effect of Prior Monaural Click on Time between Critically Fused Binaural Clicks
Authors: Frishkopf Lawrence S. , Guttman Newman
Published: September 2005

Physiological investigations in the cat have shown that latency of the N1 peripheral auditory response to the second of a pair of monaural clicks increases slightly as the interval of separation is shortened. Might this small shift in latency be detectable psychophysically as a change in the interaural time difference required to obtain critical fusion between the second click and a click in the other ear? (Criterion of critical fusion is immobility of the image upon reversal of inputs to the ears.) To test this, interaural time difference at critical fusion was studied as a function of levels of first and second clicks and of the interval between them. Results indicate that for intervals of separation of 10 and 25 msec the second click tends to lead the contralateral click in a manner compatible with the observed N1 latency shift; the observed changes in interaural time difference are generally less than 0.25 msec. For intervals less than 10 msec, fusion becomes difficult or impossible and complex effects are observed. In certain cases an effect persists for at least 240 msec.
Intelligibility of Natural and Distorted Speech Led through Ten Hearing Aids to Normal and to Deafened Individuals
Authors: Kelsey Patricia A.
Published: September 2005

Three female and two male voices were taped reading sentences which were re-recorded after being led through ten hearing aids with electroacoustic characteristics ranging from very good to poor. Normal ears and ears with varying types and degree of deafness were used. A latin square design assured proper comparisons among aids. Each listener repeated 100 colloquial sentences which were taped under a natural speaking condition, 100 under a nasal-plus-speeded condition, and 100 under an interrupted speech condition. Comparisons of normal and deafened groups in terms of percentage of words correctly understood show that the deafened group always did poorer even though corrective amplification was used. In most cases the hearing aids were ranked in similar orders by both groups within a speech category, but were ranked differently from the natural voice condition to the distorted conditions, especially by normals. The data have also been analyzed in terms of the minimum number of voices and types of speech distortion necessary to provide an adequate test battery for such purposes. Comparisons have been made between performance on each aid versus the many electroacoustic characteristics known for each aid. (This research is supported in part by the Office of Vocational Rehabilitation.)
Auditory Acuity and Speech Communications
Authors: Kryter Karl D. , Williams Carl , Green David
Published: September 2005

It appears that auditory acuity as measured by the pure tone audiometer will continue to be the primary method used for determining hearing impairment. It is also the consensus that the results obtained at various frequencies should be weighted in a way that maximizes their relation to the ability of the patients to understand everyday speech. There is disagreement, however, on the proper way to weight hearing losses for the various frequencies tested, and on the measures that should be used for evaluating the ability of persons to perceive speech. The purpose of the present study is to explore further the relation between communication and deafness as measured by pure-tone audiometry. Pure tone audiometric and recruitment tests, PB word and sentence intelligibility tests, and tests of the ability of listeners to identify talkers and to localize the source of a sound, were administered to 115 adult male soldiers. Each ear was tested separately giving a total “N” of 230. Approximately 25% of the ears would be classified as having normal hearing and 75% as having a permanent loss of 15 db or greater at one or more frequencies below 6000 cps. Preliminary results suggest that the ability to perceive speech can be predicted adequately only if different pure-tone weighting schedules are used for different patterns of deafness. Multiple regression equations for estimating hearing loss for speech from pure tone measures of acuity will be presented. (The authors gratefully acknowledge the assistance and facilities provided this project by the U. S. Army Medical Research Laboratory and Weapons Board of Fort Knox, Kentucky, and, in particular, the help provided by Captain John Fletcher of the Army Medical Laboratory and Captain David Hilding of the Army Medical Corps.) (The study was supported by Grant B-1727 of the Institute of Neurological Diseases and Blindness of the National Institutes of Health.)
Multiple Vibrational Relaxation in Gaseous CH2Br2
Authors: Meyer Norman J.
Published: September 2005

Ultrasonic speed of sound and absorption measurements have been made in gaseous dibromomethane at 296°K, and at pressures between 0.5 and 15.0 mm Hg. Wide-band transducers (solid dielectric microphone and driver) were used. A continuous selection of frequencies between 13 and 80 kc was used, generated as pulsed sine waves. Independent vibrational relaxation processes were found at 7.0 and 125 Mc/atmos, with corresponding relaxation times of 3.02×10−8 and 0.146×10−8 sec. A third relaxation process was not within the experimental range of the apparatus, and occurs below 0.1 Mc/atmos, with a relaxation time longer than 1.8×10−6 sec. Seven of the nine vibrational modes have sufficient population at 296°K to contribute to the various relaxation processes. Primarily based upon the specific heat contributions of each mode, the assignments of the various modes relaxing at the different relaxation times were made. (Supported in part by the Office of Naval Research.)
Measurement of the Ultrasonic Absorption and Velocity in Molten Salts
Authors: Higgs R. W. , Litovitz T. A.
Published: September 2005

Measurements of the ultrasonic absorption and velocity in various molten Group I nitrates, molten CdCl2 and molten mixtures of NaNo3 and KNO3 were made for different temperatures and frequencies using the pulse technique. The molten salts and molten salt mixtures were compared with various organic liquids and their mixtures and found to behave ultracoustically as associated liquids. The ratio of the bulk viscosity, ηB, to the shear viscosity, ηS, is nearly directly proportional to the volume of the cation, and the logarithm of ηB/ηS is a linear function of the entropy melting in the Group I nitrates measured. The value of ηB/ηS is as high as 10 in these salts, compared to about 3 for associated organic liquids. The value of Rao's constant has then calculated for various molten salts and is found to be approximately 1.5 as compared to 3 for many organic liquids. (Work supported by Office of Ordnance Research.)
Audience and Room Acoustics
Authors: Nickson A. F. B. , Muncey R. W.
Published: September 2005

Acoustical design will always involve a decision of the conditions required in terms of physically measurable quantities followed by design techniques aimed at achieving the required results in the final building. Studies by the authors were initially concerned with the use of acoustical models as an aid in the design techniques. The requirements for the model surfaces and two acoustical models have been studied but finally an impasse was reached when measurements sufficient for testing model similarity were not known. The response of particular listeners to music and speech in typical auditoriums and to sounds with artificially added echoes showed a reasonably broad tolerance of acoustical conditions. Different individuals had varying requirements and with program variation also the over-all tolerance for a hall is quite large. These considerations suggest that the wealth of detail supplied by acoustical measurements is not matched by any corresponding subjective response and that further search for more critical acoustical parameters will be unrewarding.
Sidney Myer Music Bowl, Melbourne, Australia
Authors: Newman R. B. , Johnson F. R. , Cavanaugh W. J.
Published: September 2005

A new enclosure for outdoor performance of music has been completed in Melbourne as a gift of the late Sidney Myer. The acoustical problem was one of exclusion of city noise (a quiet site was not available) together with as much reflective reinforcement of sound as possible. Some 2000 seats are included “inside” the enclosure with the orchestra, and another 50 000 or more people are accommodated outside on the lawns of the surrounding park. A sound amplifying system, designed by members of the Division of Building Research of the Commonwealth Scientific and Industrial Research Organization of Australia, employing time delay circuits, has been incorporated to increase the sound levels for the outdoor audience. This paper describes the acoustical design of the enclosure and the results of some preliminary observations and reverberation time measurements made during the initial “trial” season of concerts. The architects were Yuncken, Freeman Brothers, Griffiths and Simpson of Melbourne, Australia.
Orchestra Enclosure for the Tanglewood Music Shed
Authors: Johnson F. R. , Beranek L. L. , Newman R. B. , Bolt R. H. , Klepper D. L.
Published: September 2005

The 25-year old “temporary” stage shell in the Tanglewood Music Shed at Lenox, Massachusetts, needed replacement for practical reasons. This opportunity was taken to re-examine the acoustics of the shed in the light of acoustical advances during the intervening years. A new shell, designed to increase the definition and enhance the tonal balance, was completed in July, 1959 and is described in this papr. The shed seats about 6000 inside; more than 6000 on the lawn outside. The stage, which can hold a large orchestra and chorus, is enclosed at sides and rear by angled panels of the new shell. Serrated side walls are sloped inward at the top and fanned outward in plan to aid in directing sound to the audience seated in a pie-shaped sector of 110°. Above the entire stage, and extending forward approximately 14 the length of the seating area, is a canopy suspended about half-way between floor and ceiling. The canopy is made of faceted plywood triangles, in graded sizes and thicknesses, joined at corners to form a pattern that is 50% open over most of the stage. Additional panels at a higher level are placed above the podium and strings. The general positions and orientations of the canopy panels were determined, with ray analysis, to increase the definition by providing short-delay (below 50 msec) reflections from stage areas to seating areas. Certain reflectors were assigned to on-stage mixing in aid of ensembly playing, and balance among different orchestral sections was contributed by the entire design, especially the additional canopy panels which preferentially boost the string tone. The openness (up to 50%) of the canopy was designed to pass sound into the high upper volume of the shed in order to retain appreciable energy in the long reverberation (ca 2.0 sec at 500 cps full, house) which contributes to the desirable singing tone for which the shed is noted. Preliminary observations indicate that the design goals have been well met. The architect was Eero Saarinen and Associates.
Reverberation Time Characteristics of Severance Hall
Authors: Ormestad Helmut J. , Shankland Robert S. , Benade Arthur N.
Published: September 2005

Following the changes in the acoustical conditions made in Severance Hall during the summer of 1958 [R. S. Shankland and E. A. Flynn, J. Acoust. Soc. Am. 31, 866 (1959)] a series of reverberation time measurements were made during the 1958–1959 concert season of the Cleveland Orchestra. Measurements were made in the empty hall, in the hall with orchestra during rehearsals, which is also the condition for recordings, and with a full audience during the regular symphony season. Measurements were made of 38-caliber revolver shots, of fully orchestrated chords played at rehearsals by Dr. George Szell especially for our measurements, and of the endings of movements in a symphony (Mendelssohn No. 4 in A major) and a concerto (Dvořák B Minor, Op. 104) during concerts. The results show a considerable increase in the reverberation time at all frequencies as compared to the conditions existing prior to 1958. The present reverberation time with a full audience is about 1.7 sec in the mid-frequencies and rises steadily to well above 2 sec at lower frequencies. Due to the heavily upholstered seats in Severance Hall the sound absorption increment due to a full audience is unusually low. Measurements made during rehearsals have permitted a determination of the absorption by an orchestra. Reverberation times measured with microphone pickup on the main floor, in box seats, and in the balcony, are essentially the same. The measurements will be continued during the 1959–1960 concert season, especially to determine the effects of a new humidity control system which was installed during the summer of 1959.
Effective Duration of the Onset-Transient Cue to Auditory Localization
Authors: Tobias Jerry V. , Schubert Earl D.
Published: September 2005

The interaural time difference at the beginning and the end of a noise burst—labeled “transient disparity” for convenience—was varied independently of the ongoing disparity. By producing a transient cue which favored localization judgments to one side of the median plane and an ongoing cue which favored judgments to the other side, a trading relation was established, and the relative contributions of the two cues to localization were computed for a range of burst lengths. The transient cue was found to affect subject judgments for burst durations up to approximately 150 msec. For longer durations, the largest transient interaural time disparity employed (500 μsec) was too small to have any effect. For the range of duration explored −10 to 1000 msec—ongoing disparity “moves” the burst more readily than transient disparity. One hypothesis which may account for this relative effectiveness, i.e., for the apparent loss of information from the transient disparity cue, is that the relative importance of the two cues is directly proportional to the fraction of the total burst duration over which each is operative. From that hypothesis, a value of “effective onset duration” was calculated and found to lie between 2 and 4 msec. It is suggested that the inherent neural on-effect would shorten the value to approximately 1 msec. (This research was supported in part by the National Science Foundation.)
Evaluation of a Stereophonic Loudspeaker by Multiple Microphone Arrays
Authors: Carlisle Richard W. , Schwartz Arnold
Published: September 2005

There is a problem in measuring the sound distribution from a stereospeaker array to correlate the results of anechoic chamber measurements with listening tests in live listening rooms. One method which is helpful is to measure the pressure at a large number of points in the live room. A multiple microphone arrangement is described which facilitates such measurements, and its application to a stereophonic speaker system is illustrated.
Absolute Calibration of Pressure-Sensitive Hydrophones by a Thevenin's Generator Method
Authors: Beatty Louis G.
Published: September 2005

The direct application of Thevenin's theorem to a complex electromechano-acoustical network results in a technique for obtaining within a bounded region the absolute calibration of pressure-sensitive hydrophones in the lower audio-frequency range. Two electrodynamic transducers are used in addition to the hydrophone being calibrated. It must be possible to monitor the motion of the diaphragm of one transducer, and also to block (either mechanically or electrically) the diaphragm. Four electrical measurements are required. Neither impedance nor the blocking force need be measured. Calibrations have been obtained up to 1.5 kc.