bluuebunny/crossref_metadata_2025 huggingface dataset:
Proximity Image Effect in Sound Localization
Authors: Gardner Mark B.
Published: September 2005

In the absence of distance-indicating clues. the apparent position of a line-of-sight (dead-ahead) source of sound coincides with the nearest rational location.
New Approach to DL Concept from Point of View of Information Theory
Authors: Majerník Vladimír
Published: September 2005

A new measure for difference limen (DL) using only the communication properties of the auditory system is proposed. By using this measure, one can also take into account the a priori probability distribution of acoustical signals. For the uniform a priori probability distribution of acoustical stimuli and in the case of Gaussian linkage between the points of signal and sensory space, this measure passes over to the usual measure for DL known in psychophysics.
Rôle of Tonal Relevance in Auditory Fatigue
Authors: Oatman Lynn C. , Price G. Richard
Published: September 2005

A new rationale concerning the subject's attitude toward a tone during exposure was tested in an attempt to find evidence for a central factor in auditory fatigue. The subjects were instructed, in one instance, to attend to the intensity of a 40-dB SL, 4.0-kHz tone. The amount of auditory fatigue that resulted was insignificantly different from conditions in which the subjects had been engaged in metal arithmetic or reverie during similar exposures.
Perceived Rate of Monotic and Dichotically Alternating Clicks
Authors: Axelrod S. , Guzy L. T. , Diamond I. T.
Published: September 2005

Subjects compared the apparent repetition rates of trains of dichotically alternating clicks, presented at 1–40/sec, with the apparent rates of monotic trains. All dichotic rates were underestimated, the degree of underestimation varying from a few percent at 1/sec to 35%–40% from about 7.5/sec onward. The latter rate corresponds to the switching rates producing minimal intelligibility of speech presented alternately to the two ears. Unlike the results of switched-speech experiments, however, the present results appear to be unequivocally interpretable as indicating a difficulty in integrating dichotically alternating inputs into a single percept.
Variations on Marill's Detection Formula
Authors: McGill W. J.
Published: September 2005

Marill's expression for the psychometric function generated by pure tones in noise, and based on ideal detection, is shown to be obtainable directly from energy fluctuations of a narrow-band noise. The formula is then generalized to wide-band noise. Estimates of effective bandwidth using detection data are reexamined in the light of such findings.
Intensities of Aural Difference Tones
Authors: Wenner Claude H.
Published: September 2005

An aural difference tone attributed to nonlinearity of the ear was produced by the use of four pairs of pure tones, 750 and 1000, 1750 and 2000, 3750 and 4000, and 7750 and 8000 Hz. A binaural loudness balance, which demonstrated the difference tone produced by 750 and 1000 Hz at 100 dB, had a frequency equal to the numerical difference between the paired tones, and had an intensity of approximately 90 dB. Instrumentation difference tones were maintained at a level of at least 70 dB below that of the primary tones. The aural difference tone used as a monaural masking stimulus for a pure tone of 250 Hz produced more threshold shift when the pairs of tones were presented simultaneously than when each of the tones was presented individually. The masking effect of the aural difference tone is a function of the frequency and intensity of the primary tones. The spread of masking over a 2-oct range, 125–500 Hz, using 750 and 1000 Hz simultaneously as the masking stimulus, was similar to that of a 250-Hz pure-tone masking stimulus.
Optimum Linear Filter for Speech Transmission
Authors: Griffiths John D.
Published: September 2005

A common speech-communications problem is to maximize speech intelligibility over a noisy channel when the transmitter is peak-power limited. An optimum linear solution is analytically derived, and consists of a speech-processing filter in the transmitter. The degree of improvement due to use of the filter is derived for a number of bandwidths and signal-to-noise ratios. The filter was experimentally verified by articulation tests as the optimum linear configuration, and was significantly more intelligible than other filters that bounded it. Although the optimum filter depends on the noise spectrum, there is no significant difference between it and a noise-invariant filter for white or speech-shaped noise. The use of the filter is equivalent to raising the transmitter power between 1 and 10 dB, depending on the speech bandwidth and the signal-to-noise ratio.
Modal Densities of Certain Shallow Structural Elements
Authors: Wilkinson J. P. D.
Published: September 2005

The modal density of a structural element is defined as the number of resonant modes within a unit frequency interval. In this paper, expressions are presented for the modal densities of some shallow sandwich shells, orthotropic plates, shells on an elastic foundation, pretwisted plates, and plates subject to in-plane forces. The expressions are valid for elements of arbitrary shape and having any prescribed boundary conditions. It is shown that, except for the orthotropic plate, the modal density of all the elements is frequency-dependent. As the frequency increases, the modal density of the shells approaches asymptotically that of the corresponding plate. For the sandwich elements, the modal density increases with increasing frequency, whereas the modal density of monocoque elements approaches a constant value.
Acoustic and Temporal Factors in the Evocation of Startle
Authors: Hoffman Howard S. , Searle John L.
Published: September 2005

Several acoustic and temporal variables responsible for the elicitation of the rat's startle reaction were examined by measuring the subject's overt movement under each of a variety of stimulus conditions. When startle was repeatedly evoked, the response decreased in amplitude, but adaptation was slow and was not complete after 675 stimulus presentations. The threshold for startle evocation increased with repeated stimulation, but partial recovery occurred during interpolated rest periods. Startle reactions were amplified when testing occurred in a background of steady noise, but the effect was independent of the frequency components of the background stimulation. Moreover, although a relatively weak signal could inhibit the reaction to a subsequently presented intense signal, the effect was independent of the frequency characteristics of either signal. Finally, it was found that relatively weak signals could either inhibit the startle reaction to a subsequently presented intense signal or reduce response latency, depending upon the temporal relationships between the two signals. It was concluded that weak signals can activate the neural mechanisms responsible for the startle reaction, and that the occurrence of acoustic startle along with its associated inhibitory and facilitory effects is dependent upon the sensation levels of the signals, but not upon their frequency characteristics.
Improvement of Hearing Ability by Directional Information
Authors: Ebata Masanao , Sone Toshio , Nimura Tadamoto
Published: September 2005

An investigation is undertaken of the ability to hear a signal sound in the presence of noise, when the signal and the interfering sound each have a directional characteristic and are separated from each other more than a certain degree, compared with the case when both are not separated. We attempt to determine through what process in our auditory system such a phenomenon occurs. We think that, when there are many sounds coming from many directions, directional information is extracted from the neural signals from both ears in our auditory system, each sound is localized in each place or direction, and a certain particular sound is selected and listened to. There is considerable difference, in the subject's ability to hear the sound, between the case in which a subject concentrates his attention on it, and the case in which he does not. For this interpretation, “attention” is introduced. It is clarified that the function that maintains the attention leads to the selective hearing of a signal relative to its direction and timbre.
Use of Noise Bands to Establish Noise Pitch
Authors: Rainbolt Harry R. , Schubert Earl D.
Published: September 2005

In the work reported, the pitch of a band of noise, called a reference band, is determined by varying the frequency position of the center of a 12-oct band of noise, the comparison band, systematically but randomly over the full width of the reference band. The pitch of the reference band is designated as the frequency position of a 12-oct comparison band that is judged “lower” than the reference band on 50% of the trials. The method of constant stimuli was employed throughout. The reference bands, whose pitch was to be defined, included bands of various widths from 12–3 oct, and they were placed at widely varying positions over the audio-frequency range, with lower limits as low as 150 Hz and upper limits as high as 9600 Hz. The psychophysical functions indicating the changing proportion of “lower” judgments as the position of the comparison band varies from the lower edge to the upper edge of the reference band are essentially monotonic, yielding little evidence of multiple pitches, even for the wide reference bands.
New Method for the Measurement of a Small Mechanical Driving-Point Impedance
Authors: Kagawa Yukio , Kosaka Yoshihiro , Kido Ken'iti
Published: September 2005

A new method is proposed for the measurement of driving-point impedance. A vibrator built in the feedback loop of an amplifier makes it possible to measure a much smaller mechanical impedance than the effective mechanical impedance of the vibrator.
Vibrations of Rib-Stiffened Thin Elastic Plates Carrying Concentrated Masses
Authors: Laura Patricio A. , Smith Gerald A.
Published: September 2005

The present study deals with the calculation of the fundamental frequency of vibration of clamped and simply supported plates stiffened in two perpendicular directions and carrying concentrated masses. It is assumed that the stiffeners are closely spaced and that their height is moderate when compared with the thickness of the plate. Use of polynomial approximations and a variational technique simplifies the calculations considerably. The approach is also applicable in the case of plates of complicated boundary shape. Numerical calculations are presented for a clamped square plate with ribs in one direction, and the results are in good agreement with those obtained following the “orthotropic-plate” approach.
Concepts of Perceived Noisiness, Their Implementation and Application
Authors: Kryter K. D.
Published: September 2005

The concepts and methods of estimating the perceived noisiness of sounds from subjective and physical measurements are described. A general method, called Effective Perceived Noise Level (EPNL), of estimating the perceived noisiness of a single sound or a total sound environment taken over a 24-hour period is proposed, and its relations to the Effective Composite Noise Rating (ECNR) scheme are discussed. It would appear that the average threshold of general noisiness or annoyance for the sound environment of a typical residential area occurs at about 50 PNdBt for sounds measured indoors and at 70 PNdBt for sounds measured outdoors; these threshold values can be utilized to advantage in conjunction with EPNL and ECNR. The virtue of using EPNL and ECNR, which in essence, are the same in certain applications as “CNR,” “NNI,” and “Q̄” quantities developed in the U. S. A., Great Britain, and Germany, respectively, is that they can combine the variable factors of duration, number of occurrences, spectrum and intensity of sounds into a single unit that allows meaningful intercomparisons of the over-all effect upon human behavior of noises and noise environments that may differ markedly from each other in these dimensions. Tolerable limits are proposed in terms of EPNL, ECNR, CNR, NNI, and Q̄ for: a) annoyance due to noise generated and measured outdoors but heard outdoors and/or indoors; b) annoyance due to noise present indoors; and c) damage risk to the ear for noise present at the listener's ears.
Speaker Identification Based on Nasal Phonation
Authors: Glenn James W. , Kleiner Norbert
Published: September 2005

A method of automatic speaker identification based on the physiology of the vocal apparatus and essentially independent of the spoken message has been developed. Power spectra produced during nasal phonation are transformed and statistically matched. In experiments involving the identification of individual speakers out of a population of 10 speakers, an average identification accuracy of 97% was obtained. With an experimental population of 30 speakers, identification accuracy was 93%. The procedure is outlined, and the experimental evaluation of it is described.
Comments on “Farfield Spectrum of the Sonic Boom” [W. L. Howes, J. Acoust. Soc. Am. 41, 716–717 (1967)]
Authors: Zepler E. E.
Published: September 2005

This is a response to a Letter to the Editor by W. L. Howes entitled. “Farfield Spectrum of the Some Boom” [J. Acoust. Soc. Am. 41, 716–717 (1967)], clarifying his use of our formula.
Similarity Measure for Automatic Speech and Speaker Recognition
Authors: Schroeder M. R.
Published: September 2005

Different speaking rates and stress patterns are known to affect the timing of speech utterances in a nonlinear and complicated way. Time normalization is, therefore, an important prerequisite in automatic speech and speaker recognition. This note describes a new approach to speech and speaker recognition based on a time-invariant measure of “contour similarity.” The important relative timing of the different parameters representing a given utterance are preserved by the contour similarity measure defined here. The concept of contour similarity is applicable to other recognition tasks in which the available information can be represented by contours in a multidimensional space.
Evidence of Phase Shift at Caustics
Authors: Barash Robert M.
Published: September 2005

Previous analyses have indicated that a wave propagating in a refractive medium undergoes a phase shift of π/2 either at a caustic or at a turning point, depending on the method of analysis. Data from two underwater explosion experiments appear to identify the caustic as the site of the phase shift.
Comments on “Evidence of Phase Shift at Caustics” [R. M. Barash, J. Acoust. Soc. Am. 43, 378(L) (1968)]
Authors: Tolstoy Ivan
Published: September 2005

It is suggested that Barash's data may also be interpreted as illustrating a phase change due to total internal reflection.
Comments on “Sound Attenuation in Liquid-Solid Mixtures” [L. R. B. Duykers, J. Acoust. Soc. Am. 41, 1330–1335 (1967)]
Authors: McCann C. , McCann D. M.
Published: September 2005

It is pointed out that there are two incorrect assumptions in the explanation of the attenuation of sound in suspensions and marine sediments given by Duykers. These invalidate his conclusions.
Reply to “Comments on ‘Sound Attenuation in Liquid-Solid Mixtures’” [C. McCann and D. M. McCann, J. Acoust. Soc. Am. 43, 381 (L) (1968)]
Authors: Duykers L. R. B.
Published: September 2005

C. McCann and D. M. McCann point to two incorrect assumption in my explanation of sound attenuation in liquid-solid mixtures. The first, on the explanation of Urick's experimental data, is admittedly wrong, but does not affect the conclusions in my article. The second, on the introduction of a new “volume concentration” to explain Shumway's experimental data at greater volume concentrations, is right, but was correctly criticized owing to the unfortunate omission of a prime in my article. The conclusions in that article are still valid.
Time and Frequency Characteristics of an Acoustic Signal Reflected from a Rough Boundary
Authors: Martin J. J.
Published: September 2005

This paper contains an analysis for determining the time of arrival and Doppler-frequency characteristics of a pulse transmitted to a target by reflection from a not-too-rough surface such as the sea bottom and gives numerical values for a typical sonar application. The analysis may be important in sonar signal processing associated with one-way or round-trip transmission and in the interpretation of data from marine geophysical surveys; it may, in addition, have application to propagation of electromechanical waves by ionospheric refraction.
Relations of the Human Vertex Potential to Acoustic Input: Loudness and Masking
Authors: Davis Hallowell , Bowers Clyde , Hirsh Shirley K.
Published: September 2005

The rate of increase of amplitude of V (vertex) potentials with the SPL of tone bursts is very slow. In one experiment, the exponent of the power law was 0.15 at 250 Hz, 0.11 at 1000 Hz, and only 0.08 at 4000 Hz. Individual differences across subjects seemed more important than the interval between stimuli (1 sec vs 3.2 sec), and variability across trials often obscured the relation to intensity. In the presence of appropriate bands of masking noise, the input-output curves rise abruptly from the masked threshold to approach the unmasked amplitude at a level about 30 dB above the corresponding masked threshold. The effect resembles recruitment of loudness. Tone pips and tone bursts of different frequency that were judged equally loud evoked slow V potentials of approximately equal amplitude. In some subjects, however, bursts of white noise evoked significantly larger responses than equally loud tone bursts or pips. In spite of the partial similarities between them, the amplitude of the V potential and the sensation of loudness are related differently to the parameters of the acoustic stimulus.
Single-Unit Activity in the Primary Auditory Cortex of Unanesthetized Cats
Authors: Goldstein Moise H. , Hall Joseph L. , Butterfield Bruce O.
Published: September 2005

Activity of single cells in cats immobilized with gallamine triethiodide was recorded with metal microelectrodes and displayed by an on-line dot display. Tone burst, noise burst, click, and other stimuli at moderate intensities were presented through condenser microphones at both ears. Spontaneous activity ranged from less than 1 spike/sec to greater than 40 spikes/sec. Almost all units were affected by acoustic stimuli, either by enhancement of activity, reduction of activity, or a combination. Units were affected at the onset and/or termination of a stimulus, throughout a stimulus, or a combination. Best frequency of units ranged from less than 1 kHz to greater than 50 kHz. Over half the units responding to tone bursts exhibited a response range greater than 12 oct. Some units had double response ranges. The pattern of response to tone bursts of some units changed as the frequency of the stimulus was changed. A minority of the units showed responses only to special stimuli such as swept tones or continuous noise or tones. It appears that the coding of acoustic stimuli by single units of the primary auditory cortex of the cat is performed in a highly individualistic and variegated manner.
Representation of Binaural Stimuli by Single Units in Primary Auditory Cortex of Unanesthetized Cats
Authors: Hall Joseph L. , Goldstein Moise H.
Published: September 2005

The stimulus-evoked activity of single units in the left primary auditory cortex (AI) of cats immobilized with gallamine triethiodide was observed as tone bursts, noise bursts, or clicks were presented at a moderate intensity to the right ear, to the left ear, and simultaneously to both ears. The right ear is represented more strongly in that more cells respond to monaural stimulation of the right ear than the left ear. An ear is said to be “represented” if a unit responds to stimulation of that ear, or if the response to stimulation of the other ear is modified by stimulation of that ear. There is extensive overlap of the populations of units representing the two ears; the population representing the left ear is almost completely contained within the larger population representing the right ear. The majority of units exhibited some form of binaural interaction. Binaural summation was the most common form of interaction; other units exhibited binaural inhibition or combinations of summation and inhibition.
Effect of Tetrodotoxin and Procaine on Cochlear Potentials
Authors: Konishi Teruzo , Kelsey Elizabeth
Published: September 2005

Tetrodotoxin or procaine was introduced into the scala tympani or scala media. The cochlear potentials—including the negative potential in the organ of Corti—were recorded before, during, and after the introduction. Tetrodotoxin at a concentration of 5 × 10−8 and 1 × 10−7 g/ml blocked the action potential but had little effect on the resting potential and cochlear microphonic, when it was introduced into the scala tympani. On the other hand, the cochlear microphonic and action potential were depressed by 0.05%–0.1% procaine introduced into the scala tympani, whereas the endocochlear potential showed a temporary increase. The mechanism underlying the generation of the receptor potential is discussed, and it is concluded that the production of the cochlear microphonic depends on the presence of potassium ions in the endolymph.
Impedance at the Eardrum, Middle-Ear Transmission, and Equal Loudness
Authors: Ross Strange
Published: September 2005

Acoustic impedance at the eardrum was measured on three subjects as a function of frequency (20 cps to about 1000 cps) and intensity (minimum 65 dB SPL; maximum 150 dB SPL, at eardrum) of a sustained ipsilateral sinusoidal stimulation by means of an inversely driven Zwislocki acoustic bridge. At lower intensity levels, acoustic impedance was independent of level, resistance and reactance varying with frequency according to R = af−1/2 and X = bf−3/4, respectively, from 20 cps to about 300 cps; above 300 cps, resistance remained essentially constant, and negative reactance decreased rapidly. At higher levels, one subject showed variations in impedance attributable to the acoustic reflex. At levels above 120 dB SPL, all subjects showed a rapid decrease of both impedance components at all frequencies. Middle-ear attenuations calculated from the magnitude of the acoustic impedance, together with previously obtained equal-loudness contours for the participating subjects, support the hypothesis that equality of loudness between two tones is attained when both generate the same total number of neural impulses within about 200 msec. The decrease in impedance at the highest levels is attributed to subharmonic radiation from the eardrum and/or a shift in the axis of rotation of the ossicles.
On the Absorption of Sound in Humid Air at Reduced Pressures
Authors: Harris Cyril M.
Published: September 2005

Measurements have been made of the absorption of sound in air as a function of humidity in the frequency range from 2500 to 8000 Hz at pressures in the range from 0.2 to 0.9 atm, at a constant temperature of 20°C, employing measurement techniques of an earlier study at atmospheric pressure. The results show that, at a given frequency, a plot of molecular absorption versus humidity has a maximum value that is independent of pressure in the range of pressures from 0.4 to 1.0 atm. The effect of lowering the pressure is to shift the peaks in the curves of absorption versus humidity to lower values of relative humidity.
Ray Representation of Diffraction Effects in the Split-Beam Sound Field
Authors: Murphy E. L.
Published: September 2005

A generalized WKB-type approximation is applied to sound propagation in the split-beam sound field to investigate diffraction effects associated with turning-point regions where ordinary WKB or geometrical-optics approximations fail. Transmission and reflection coefficients are obtained. In some regions where asymptotic expansions for the generalized WKB solutions are valid, ray representations can be developed for some of the diffraction effects. Limitations on the validity of these ray representations and the extent of the regions (including the geometric shadow) in which diffracted rays may be introduced are discussed. Simple geometric schemes can, under certain conditions, be introduced relating particular diffracted rays to corresponding geometrical rays.
Ray Theory Applied to a Wide Class of Velocity Functions
Authors: Pedersen Melvin A.
Published: September 2005

Ray-theory expressions for the range, travel time, and intensity are developed for a newly formulated sound-velocity profile model in which the velocity is expressed as a series in integral and half integral powers of ocean depth. By the process of series inversion, any analytic function for which the first and second depth derivatives do not vanish simultaneously can be cast into this model. The series inversion process is applied to several elementary velocity functions, demonstrating that the general function solutions reduce to ray theory solutions obtainable by direct methods. Procedures and numerical examples for fitting experimental underwater-sound-velocity data to the model are presented. Acoustic artifacts, such as artificial layering effects, can be minimized because each layer may contain an arbitrary number of parameters and because the velocity and an arbitrary number of derivatives may be matched at layer interfaces.
TTS with Auditory Task during Exposure
Authors: Melnick William
Published: September 2005

Less TTS was measured at 1400 Hz following a 2 min exposure to 1000 Hz at 110 dB SPL when, simultaneously with the exposure, the listeners were required to trace threshold for 250 Hz in the nontest ear than when the listeners were passively exposed to the intense signal during this interval.
Noise-Criterion Curves for Use with the USASI Preferred Frequencies
Authors: Schultz T. J.
Published: September 2005

Slightly revised, corrected versions of Beranek's noise-criterion curves are presented.
Comments on “Numerical Solution for Transient Scattering from a Hard Surface of Arbitrary Shape—Retarded Potential Technique“ [K. M. Mitzner, J. Acoust. Soc. Am. 42, 391–397 (1967)]
Authors: Shaw Richard Paul
Published: September 2005

A modification of the fundamental equation used in the above paper is suggested to allow for the inclusion of discontinuous incident wavefronts.
Damped Oscillations of a Bubble in an Extended Liquid
Authors: Barnes C. , Anderson D. V.
Published: September 2005

The equations of acoustics are solved generally for the resonant frequencies and damping of a sphere pulsating radially in a surrounding fluid or different acoustical properties. The known results for a bubble of gas in a liquid are derived as a limiting case.
Transient Analysis of the Propagation of an Electric Pulse in a Piezoelectric Plate
Authors: Paul H. S.
Published: September 2005

Transient analysis of the propagation of waves due to an electric-potential pulse concentrated at a point on the boundary of a piezoelectric plate of crystal class 6mm is carried out. Normal stress is analyzed for an exponential pulse and a step pulse. Numerical results are obtained for a cadmium selenide crystal.
Acoustical Radiation Field of a Spherical Condensation
Authors: Barnes C. , Anderson D. V.
Published: September 2005

The sound radiated by the sudden release of a uniformly condensed sphere of fluid surrounded by an extended uncondensed fluid of different acoustical properties has a characteristic sawtooth pattern, a consequence of repeated reflections inside the sphere. The form of the pattern depends on the relative densities and speeds of sound in the two media.
Fluctuations in Low-Frequency Acoustic Propagation in the Ocean
Authors: Nichols R. H. , Young H. J.
Published: September 2005

An experimental study has been made of the variability of acoustic transmission in the ocean at frequencies around 270 cps between a fixed bottomed source and fixed bottomed receivers. Transmitted signal level was observed at two distances: 2 and 700 NM (nautical miles), over periods ranging from 1 to 22 h. Simultaneous measurements were made at several hydrophones at each location to investigate correlation of fluctuations at various pair spacings. Two types of variation were noted. At the 2-mile range, quasiperiodic variations in level occurred with a predominant frequency of 0.12 cps, similar to that of surface waves. These are believed to be due to multipath interference of signals reflected one or more times from the moving surface. At the 700-NM range, such variations were also observed; in addition, large slower fluctuations were observed, with periods of a few minutes to several hours. These are believed to be due to changing multipath interferences among signals passing through moving or changing water masses of different refractive indices (e.g., internal waves). Cross-correlation coefficients of either type of fluctuation were small: 0.1–0.2 at pairs of hydrophones with spacings of 25–1815 ft.
Assessment of Footstep Noise through Wood-Joist and Concrete Floors
Authors: Olynyk D. , Northwood T. D.
Published: September 2005

A technique for rating floors for impact-sound insulation by subjective comparisons of the sounds of transmitted footsteps is described. The subjective judgments were used as a criterion for checking objective ratings obtained with the standard ISO impact machine. A previous study was done in the laboratory on variations of a reinforced concrete-slab floor. Further observations have now been made in typical buildings, with special attention to wood-joist floors. For the whole study, the correlation between subjective and machine ratings is limited in range if the usual shape of reference contour, adopted for example by the U.S. Federal Housing Administration, is used. This contour makes the results, especially for hard-surfaced concrete floors, dependent on high-frequency noise that is characteristic of the machine rather than of actual footsteps. A better correlation is obtained by changing from the present FHA reference contour to one that reduces the emphasis on high frequencies.
Effects of Varying Attenuation Rate and Starting Intensity on Békésy Threshold
Authors: Harbert F. , Young I. M.
Published: September 2005

Békésy fixed-frequency initial threshold and threshold of equilibrium for pulsed and continuous tones were compared for different starting intensities in normal and pathological ears. For pulsed tones, the initial threshold as measured by the bottom of the first spike was not significantly affected by varying attenuation rates or starting intensities in normal ears and in pathological ears without abnormal adaptation. For abnormally adapting ears, higher thresholds were usually produced by suprathreshold than by infrathreshold starting intensity. Halving the attenuation rate produced about 1.5-dB elevation of continuous-tone thresholds for a given suprathreshold starting intensity in normals and cochlear lesions. Each 20-dB increase in the suprathreshold starting intensity produced about 1.5-dB elevation of continuous-tone thresholds in normal ears. In cochlear lesions, the elevation amounted to 5 dB. Threshold at equilibrium was unchanged in all ears regardless of starting intensity level.
The Ear as a Frequency Analyzer. II
Authors: Plomp R. , Mimpen A. M.
Published: September 2005

Previous experiments on the limit of the ear's frequency-analyzing power, carried out with only two subjects, were repeated for four other subjects. The limit was investigated by measuring the number of harmonics of a complex tone that can be heard separately. It was found that, even under the most favorable conditions, not more than the first five to seven harmonics can be distinguished. This limit agrees with the critical-band concept, that is to say, a partial of a multitone stimulus can be heard only when the adjacent tones are separated by more than the critical bandwidth.
On the Relation between the Acoustic Reflex and Loudness
Authors: Ross Strange
Published: September 2005

For each of four subjects, a set of equal-loudness contours constructed from obtained loudness balances was compared to contours of contra- or ipsilateral sinusoidal stimulations that activate the acoustic reflex to the same degree, as indicated by a constant change in acoustic impedance at the eardrum. Two subjects produced “normal” equal-loudness contours, showing close coincidence with the respective equal-reflex contours; the remaining two subjects produced “abnormal” equal-loudness contours, exhibiting significant departures from the respective equal-reflex contours. Results indicate no systematic difference in the sensitivity of the acoustic reflex to ipsi- and to contralateral stimulation. Middle-ear attenuations calculated from the magnitude of the acoustic impedance at the eardrum, together with estimates of the reflex-generated attenuations, were employed to transform the sound-pressure levels (SPL's) of the equal-reflex contours to relative values of volume velocity of the cochlear fluid. The transformed contours support the hypothesis that the acoustic reflex is activated to the same degree by sinusoidal stimulations producing the same total number of neural impulses within about 200 msec. For some subjects, equality of loudness between two sinusoidal stimulations appears to be attained under this same condition.
Frequency Dependency of Aural Difference Tones
Authors: Wenner Claude H.
Published: September 2005

Aural difference tones ranging from 125 to 3000 Hz were produced by primary tones between 1900 and 7700 Hz, wherein the normal threshold in decibels (re 0.0002 μbar) is relatively similar. Using difference tones as a masking stimulus for pure tones of the corresponding frequency, masked thresholds were obtained when the primary tones ranged in intensity from 60 to 110 dB SPL. The masking effect of the difference tones does not become apparent until the intensity of the primary tones reaches a level of 60 to 70 dB, after which there is a constant growth in the masking effect for each 10-dB increase in the intensity of a given set of primary tones. Threshold shift due to the use of the difference tone as a masking stimulus is not dependent upon the frequency of the difference tone, but is a constant value for a given intensity and a group of primary tones. There is an inverse linear relationship between the intensity of the difference tone to that of the frequencies of the primary tones used to produce it. A maximum amount of threshold shift occurs in the vicinity of 650–1000 Hz, owing to resonance, and manifests itself when the primary tones have an intensity level of 80 dB or more.
Spectrographic Analysis of Divers' Speech During Decompression
Authors: Brubaker Robert S. , Wurst John W.
Published: September 2005

The distorting effects of a pressurized helium environment on the speech of three experienced divers at five depths of submersion were studied by means of spectrography. The results indicate that under such conditions, vocal fundamental, vowel formants, and consonant-vowel amplitude ratios are elevated. Implications for helium-speech processing are presented, and the results are interpreted as consistent with the hypothesis that, in addition to the helium and pressure effects, increased vocal effort contributes to speech distortion in such environments.
Vocoder Filter Design: Practical Considerations
Authors: Golden Roger M.
Published: September 2005

Design optimization procedures for vocoder bandpass filters have evolved as a result of successful digital computer simulations of voice-excited vocoders and spectrum channel vocoders. These procedures yield designs that result in improved performance of the channel vocoder. The procedures, implemented by computer programs, permit choosing the proper response characteristics for the various bandpass and low-pass filters required in a channel vocoder. Examination of response curves shows why the nearly critical-damping time characteristics of Bessel designs are preferred compared to the underdamped, although relatively constant, magnitude response of Butterworth and elliptic designs. In addition to impulse response, consideration is also given to: (a) Filter spectral-resolving power (i.e., passband and attenuation-band characteristics); and (b) filter magnitude-phase characteristics at the frequency crossover point of contiguous filters. For vocoder designs employing unequal bandwidth filters, channel characteristics may be preserved either by using higher-order filters for the wider frequency bands or by combining an appropriate number of narrow-band equal-bandwidth filters in parallel. Attention to magnitude-phase characteristics requires evaluation of resultant gain at different crossover frequencies when two filters are combined in parallel. This evaluation is performed for filters combined with and without phase inversion and leads to a choice of a proper bandwidth scale factor. Such evaluation also shows why vocoder performance can sometimes be improved by shifting the phase of alternate channels by 180°.
Properties of a Low Temperature Coefficient Resonator Plate of Ammonium Dihydrogen Arsenate (ADA). II
Authors: Adhav R. S.
Published: September 2005

The properties of a 70° X-cut ADA crystal resonator, vibrating in extensional mode and suitable for narrow-band filtering in the range 20–200 kHz, are described. The resonator possesses a low temperature coefficient of frequency of −30 ppm/°C and a c0/c1 ratio of 200. The orientation of the resonator is critical for selecting a desired c0/c1 ratio, which varies from 180 to 320 as the orientation is changed from 68° X to 78° X, while the temperature coefficient varies from −38 to −8 ppm/°C. The Q of the resonator, measured in air, is nearly 5000; and 60% of the length of quartz resonator is required to obtain the same resonant frequency.
Variation of Ultrasonic Grain-Scattering Factors with Velocity
Authors: Papadakis Emmanuel P.
Published: September 2005

This paper explores the dependence of ultrasonic grain-scattering attenuation in a polycrystalline aggregate upon the various methods of determining the elastic-wave velocities in the aggregate. High powers of the velocities appear in the denominators of the grain-scattering factors, so small errors in velocity will produce disproportionately large variations in the scattering factors. The elastic-wave velocities in the aggregate may be measured directly on the attenuation specimen or may be computed from the elastic moduli of single crystals of the material by the methods of Voigt or Reuss. These two methods are approximate and yield different values for the velocities. Usually the experimental velocities will fall between the Voigt and Reuss velocities. Because of the velocity dependence of the scattering factors, the attenuation predicted from Voigt and Reuss velocities will differ considerably in most materials. The variability of the scattering factors with velocity will be explored. In this paper, the ultrasonic grain-scattering factors are computed and compared for several materials using experimental velocities, theoretical Voigt and Reuss velocities, and the average theoretical velocity (VOIGT+REUSS)/2. It is shown that the scattering factors computed from the experimental velocities often agree with those from the average theoretical velocities to within 20% to 50%. Measured attenuation usually agrees with predictions made in this manner to within a factor of 2.
A Matter of Dates
Authors: Waterhouse Richard V.
Published: September 2005

Comment is made on the term of office of Martin Greenspan, President of the Acoustical Society of America, as reported in J. Acoust. Soc. Am. 42, 1354 (1967).
Notes on the Sound-Transmission Loss of Residential-Type Windows and Doors
Authors: Bishop Dwight F. , Hirtle Parker W.
Published: September 2005

Sound-transmission-loss data for several residential type windows and doors are presented.
Interference between Two Simple Tones
Authors: Plomp R. , Steeneken H. J. M.
Published: September 2005

For various frequencies, 20 subjects adjusted the Δf value of two simple tones after two criteria: (1) maximal roughness and (2) absence of interference and hearing the tones separately. The average results agree rather well with some old data published by Cross and Goodwin (1893) and by Mayer (1894). Over a restricted frequency range, the results obtained for Criterion 2 agree with critical bandwidth.
Numerical Evaluation of the Radiation Impedance for a Piston in a Nonrigid Baffle
Authors: Feit David , Duncan Mary E.
Published: September 2005

The radiation impedance for a circular piston in a nonrigid baffle is determined numerically. A low-frequency analytic approximation for the resistive impedance is determined and compared to the numerically obtained results.
Sector Coverage Using Multibeam Linear Arrays
Authors: Doolittle R. D.
Published: September 2005

A universal parameter is developed, whereby the sector coverage of a line array of N, equally, spaced elements may be computed easily. The sector coverage is defined as the number of steered beams with their steering angles that will cover a given angular sector with a specified minimum response. An example of the method is worked out and a table of values for the universal parameter is presented for N = 8 to 80.
Frequency Spectrum of N Waves with Finite Rise Time
Authors: Oncley P. B. , Dunn D. G.
Published: September 2005

Several investigators have derived expressions for the pressure spectrum of the sonic-boom N wave. Where the rise time is zero, Howes has shown that the pressure spectrum is a published spherical Bessel function. The present analysis shows that the spectrum with a finite rise time, not exceeding one-tenth of the duration, can be closely approximated by multiplying two spherical Bessel functions, or, equivalently, by adding their logarithmic curves.
Deep-Sea Noise Due to Surface Motion
Authors: Kuo E. Y. T.
Published: September 2005

A physical model is proposed for the deep-sea ambient noise. Ambient noise is hypothesized to be caused by the high-frequency caipllary patches that are randomly distributed over the ocean surface. The random surface-roughness spectrum implied by the ambient-noise measurements and that implied by the hypothesis are discussed. The results are found self-consistent and comparable to those of other investigators. They also agree with the idea of convolution radiation (proposed by) Longuet-Higgins, Marsh, and Kuo. The analysis strongly indicates simple relationship among the physical parameters controlling ambient noise, noise frequency f, noise direction θ, and the sea state (implied by λw). The relationship is given by 2π/λw = 2πf sinθ/cw, where λw is energy containing gravity wavelength, cw is acoustic velocity in the water, and θ is radiation direction with respect to the normal of the mean sea level. When one physical parameter was arbitrarily held constant, the other two physical parameters varied consistently with actual measurements.
Fluctuation in Horizontal Acoustic Propagation over Short Depth Increments
Authors: Whitmarsh D. C. , Leiss W. J.
Published: September 2005

Underwater acoustic-propagation measurements have been made off Key West, Fla., for the past 3 yr. Two or three deep-submergence vehicles were allowed to sink freely and simultaneously through the water to depths as great as 5000 ft while transponding acoustically with each other. Pulses at frequencies of 10, 20, and 40 kHz and horizontal ranges of 1700 to 8000 yd were used in the experiment. Because direct acoustic signals showed amplitude fluctuations of approximately 15 dB for depth changes of 15 20 ft, a method of rapid pulsing was installed. This allowed the emission of discrete signals 0.25 sec apart over a period of 5 sec periodically during an operation. Amplitude fluctuations for depths changes of only a few inches could be measured. Pulse-to-pulse amplitude differences of up to 15 dB were found for depth changes of as little as 10 in. These fluctuations are discussed in terms of transmission loss and are compared to the losses suffered for the larger depth changes and for those predicted by ray theory on the basis of the measured sound-velocity structure of the water. It is concluded that refraction conditions can account for the fluctuation.
Spurious Pressure Fluctuations in Wind Tunnels
Authors: Wills J. A. B.
Published: September 2005

Wall pressure spectra measured in wind tunnels usually exhibit a pronounced rise at low frequencies, in conflict with theoretical predictions and with those experiments carried out without the constraint imposed by the wind tunnel. Some wind tunnel experiments are described to show that typically the spurious disturbances arise in the first diffuser and travel upstream as acoustic waves. Removal of the diffuser produces a spectrum falling at low frequencies.
Practical Problems of Partition Design
Authors: Ford R. D. , Lord P.
Published: September 2005

It is proposed that partitions should be classified according to the insulation that is required. Up to 35 dB, a single-wall construction may be used; but, for an average transmission loss of 40 dB or more, it is more efficient to use a double-leaf type of construction. A given insulation may then be obtained either with light leaves and a large cavity or with heavy leaves and a small cavity. The difficulties associated with both single and double walls are discussed, and it is shown that, with care, the detrimental effects of both wall and cavity resonances may be either eliminated or very much reduced. The classical theory for double-wall transmission is found to be inadequate; but an empirical design formula gives good agreement with measured average values.
Practice Effects in the Absolute Judgment of Pitch
Authors: Cuddy Lola L.
Published: September 2005

Three experiments are reported in which the relation between practice and the absolute judgment of pitch was examined. Experiment 1 showed that students with training in music could judge pitch more accurately than students with little or no music training. In Expts. 2 and 3, listeners were given systematic training that stressed the identification of a single reference standard −A4, 440 Hz. Following such training, listeners showed improved recognition of A4 (Expt. 2) and improved recognition of a series of 10 tones (Expt. 3). Training on the reference standard A4 was more effective in improving the performance of music students than was training in which the listener was required to name each tone and was then told the correct response (regular feedback).
Some Properties of Longitudinal Shear Waves: A Study by Computer Simulation
Authors: Khanna Shyam M. , Sears Richard E. , Tonndorf Juergen
Published: September 2005

Shearing between the basilar membrane and tectorial membrane is known to contribute towards mechanical processing of the auditory signals. The amplitude of the longitudinal shear wave has been given by von Békésy to be proportional to the vertical amplitudes of the basilar membrane and the first space derivative of the momentary position of the traveling wave along the basilar membrane. Traveling waves were generated on a digital computer using a modified form of Flanagan's mathematical model. Shear waves were obtained from these by taking the first instantaneous space derivatives. Envelopes for the longitudinal shear vibrations are compared to those of the traveling waves. These comparisons show that: (1) The maxima of the shear wave envelopes are slightly closer to the helicotrema. (2) The shear waves are much more localized along the basilar membrane. (3) Localization is much more pronounced at low frequencies than the equivalent entities of the traveling wave. Comparisons made between the resonance curves of traveling-wave vibrations and shear-wave vibrations show considerable sharpening of the shear-wave envelopes towards the low frequencies. The effect of middle ear transmission on the resonance curves is shown.