Showing papers in "Journal of the Acoustical Society of America in 1981"

Nine‐term equation for sound speed in the oceans

Abstract: A simple yet accurate nine‐term, eight‐variable equation for sound speed in the oceans, suitable for programmable pocket calculators, is presented. Ranges of validity encompass: temperature −2° to 30° C, salinity 30° to 40°/°°, and depth 0 to 8000 m. Good quality oceanographic data at 15 worldwide stations, including two in the Mediterranean, were utilized for the computations. The Del Grosso and Mader [J. Acoust. Soc. Am. 52, 961–974 (1972)] sound‐speed equation was employed as ’’truth’’ after comparisons among Wilson [J. Acoust. Soc. Am. 32, 641–644. 1357 (1960)] and others. A precise method of computing pressure is detailed. Practical differences in critical depth, excess depth, conjugate depth, deep sound‐speed gradients, and echo‐sounder corrections are shown to be small between computations based on Wilson or Del Grosso and Mader sound‐speed equations.

Kramers–Kronig relationship between ultrasonic attenuation and phase velocity

Abstract: Kramers-Kronig relations linking the attenuation and dispersion are presented for a linear acoustic system. These expressions are used as a starting point to derive approximate, nearly local expressions relating the ultrasonic attenuation at a specific frequency to the local frequency derivative of the phase velocity (i.e., dispersion). The validity of these approximate relationships is demonstrated in several acoustic systems exhibiting substantially different physical properties.

Poroelasticity equations derived from microstructure

Abstract: Equations are derived which govern the linear macroscopic mechanical behavior of a porous elastic solid saturated with a compressible viscous fluid. The derivation is based on the equations of linear elasticity in the solid, the linearized Navier–Stokes equations in the fluid, and appropriate conditions at the solid–fluid boundary. The scale of the pores is assumed to be small compared to the macroscopic scale, so that the two‐space method of homogenization can be used to deduce the macroscopic equations. When the dimensionless viscosity of the fluid is small, the resulting equations are those of Biot, who obtained them by hypothesizing the form of the macroscopic constitutive relations. The present derivation verifies those relations, and shows how the coefficients in them can be calculated, in principle, from the microstructure. When the dimensionless viscosity is of order one, a different equation is obtained, which is that of a viscoelastic solid.

Piezoelectricity in polyvinylidenefluoride

Abstract: A review of the physical properties of polyvinylidenefluoride (PVDF) with particular emphasis on its piezoelectric activity is given and the applications of this material are discussed. PVDF is a semicrystalline polymer whose crystalline domains appear in four different forms. These forms may be interconverted by the application of heat, electrical fields, and pressure. Thermal poling or corona poling will orient the molecular dipoles in the crystalline parts and thus yield a permanent polarization. This polarization causes, by means of differences in the dielectric and elastic properties of the amorphous and crystalline parts, the piezoelectricity of PVDF. The piezoelectric constant d31 reaches values of about 35 pC/N at room temperature. At decreasing temperatures a drop of d31 and d33 is observed. Compared to other piezoelectric materials, PVDF has such unique properties as flexibility, ruggedness, availability as thin films, and low acoustic impedance, but a somewhat smaller electromechanical coupling factor. Applications of PVDF are in transducers for audiofrequency, ultrasonic, underwater, and electromechanical use and in pyroelectric and optical devices.

Active adaptive sound control in a duct: A computer simulation

Abstract: Most active sound cancellation systems reported in the literature use open‐loop control, depend on near‐zero phase delay in control system elements, and require constant acoustic signal transit time from a signal pickup (microphone) to a control sound source (loudspeaker). The applicability of such systems can be significantly enhanced by using closed‐loop control. This study concerns a digital computer simulation of adaptive closed‐loop control for a specific application, sound cancellation in a duct. The key element is an extension of Sondhi’s adaptive echo canceler and Widrow’s adaptive noise canceler from signal processing to control. The adaptive algorithm is thus based on the LMS gradient search method. The simulation shows that one or more pure tones can be canceled down to the computer bit noise level (−120 dB). In the presence of additive white noise, pure tones can be canceled to at least 10 dB below the noise spectrum level for SNR’s down to at least 0 dB. The underlying theory implies that the algorithm allows tracking tones with amplitudes and frequencies that change more slowly with time than the adaptive filter adaptation rate. The theory implies also that the method can cancel narrow‐band sound in the presence of spectrally overlapping broadband sound. The method can be applied more widely, particularly to control systems that involve transport delay.

Review of transient field theory for a baffled planar piston

Abstract: The theoretical approaches which have been used to study the velocity potential and pressure fields radiated by a planar piston source vibrating in an infinite rigid baffle are broadly reviewed and discussed with emphasis on the basic mathematical methods employed. Attention is focused on those aspects of piston theory directly related to the point or spatially averaged transient field of a pulsed piston radiator. Studies of the nonuniformly vibrating piston are also reviewed. Much of this material has not been previously compared, so where possible common origins and general relationships are stressed.

Speech acoustic‐cue discrimination abilities of normally developing and language‐impaired children

Abstract: The ability of 35 language impaired (LI) and 38 normally developing children between the ages of 5 and 8 1/2 yr to discriminate between speech stimuli, using an operantly conditioned, nonverbal motor response, was investigated. Six syllable contrasts ([ba] versus [da], [da] versus [ta], [e] versus [F], [dab] versus [dFb], [sa] versus [sta], and [sa] versus [Fa]) were selected to investigate discrimination of various temporal and spectral cues. Results demonstrated that the LI group made most errors discriminating syllables which were differentiated by consonants and fewest errors on those differentiated by vowels. The normal group made most errors discriminating between syllables including fricatives and brief vowels and fewest errors on stimuli differentiated by stop consonants or vowels in context. The LI group was significantly poorer than the normals in discriminating all syllables that incorporated brief temporal cues followed rapidly in succession by other acoustic cues. They also were impaired in discriminating [sa] versus [Fa]. They were unimpaired discriminating stimuli differentiated by vowels. It is suggested that the particular constraints demonstrated by LI children in their nonverbal and speech processing abilities may be attributed to abnormalities in mechanisms involved in auditory masking.

Acoustic radiation pressure produced by a beam of sound

Abstract: The second‐order force produced by a sound beam directed normally at a plane target is calculated. Previous theories on acoustic radiation pressures associated with plane acoustic waves are examined critically and erroneous results, where they exist, are noted and rectified. A number of general relations are established using a new approach which avoids the necessity of dealing with detailed solutions of the governing nonlinear equations. Some of the concepts inferred from known solutions obtained by previous authors require drastic revision in the light of the present study. Specifically, the notion that Rayleigh radiation pressure depends on the nonlinearity of the medium (while Langevin radiation pressure does not) is not true in the case where the medium is bound by a partially reflecting wall. Again, that the concept that Rayleigh radiation pressure depends on the acoustic field only through the energy density of the field is shown to be false. In one instance it is shown to depend also on how the field is maintained, while in another instance it does not appear to depend on the mean energy density of the field at all.

Reflection of acoustic waves at a water–sediment interface

Abstract: Reflection and refraction of plane acoustic waves are studied for the case where the sediment is modeled as a porous viscoelastic medium. The model is based on the classical work of Biot which predicts that three different kinds of attenuating body waves may propagate in the sediment. As a consequence when homogeneous plane waves in water are incident to a water‐sediment interface, three nonhomogeneous waves are generated in the sediment. In these waves the direction of phase propagation and the direction of maximum attenuation are not the same and particle motion follows an elliptic path. Moreover, the velocity and attenuation of the refracted waves become dependent on the angle of incidence and no “critical” angle occurs. Numerical examples show that the reflectivity of a porous viscoelastic model differs significantly from the case where the sediment is modeled as a viscoelastic solid with constant complex modulus. Finally, because of the frequency dependence of reflectivity in the porous model, it is ...

Relationship between collagen and ultrasonic backscatter in myocardial tissue

Abstract: The relationship between ultrasonic backscatter and collagen concentration estimated on the basis of hydroxyproline concentration was examined in hearts from normal dogs and in hearts from dogs subjected to ischemic injury by coronary occlusion as an approach toward elucidating the physical mechanisms underlying the scattering of ultrasound by soft tissue. Ultrasonic backscatter was found to increase significantly in regions of ischemic injury studied 5–17 weeks following occlusion. The average backscatter coefficient was six times larger in regions of infarct studied 8–10 weeks after occlusion than that in regions of infarct studied 5–6 weeks after occlusion. In contrast, the average hydroxyproline concentration, a quantitative index of molecular collagen content, for regions of infarct was only about 25% larger at 8–10 weeks compared with that at 5–6 weeks after occlusion. These results may suggest that the magnitude of ultrasonic scattering in regions of remote myocardial infarct is sensitive not only ...

Spontaneous narrowband acoustic signals emitted by human ears.

Abstract: In the ears of many persons, a spontaneous and continuous narrowband acoustic signal can be measured with a probe microphone in the ear canal. In a sample of 32 persons with normal hearing who were tested bilaterally, an oto‐acoustic emission (OAE) was detected in 22 ears of 16 persons. These signals were most often found between 1.0 and 2.0 kHz and in all cases, the sound pressure in the occluded ear canal was less than 200 μPa. The behavior of these emissions was investigated in a number of experiments on the author’s own OAE at 1910 Hz. In one of these studies, the suppression of an OAE by an external tone was examined. It was found that a contour of constant suppression (amplitude versus frequency of external tones that produce a criterion reduction in the amplitude of the OAE) exhibits frequency selectivity like that commonly associated with cochlear frequency analysis. The existence of OAE’s of cochlear origin demonstrates that the ingredients for active biomechanical processes are present in the inner ear and supports the notion that such processes increase the sensitivity and selectivity of mechanical frequency analysis in the cochlea.

Discrimination of speech by nonhuman animals: Basic auditory sensitivities conducive to the perception of speech‐sound categories

Abstract: Chinchillas (Chinchilla laniger) were tested in a same–different task to determine the location of greatest sensitivity along a continuum of voice‐onset‐time (VOT). The procedure used was an up–down staircase technique which allowed the determination of the just‐noticeable‐difference in VOT (Δ VOT) for VOT’s on a continuum ranging from [dα] to [tα]. Results demonstrated that the animals were most sensitive to change (i.e., produced the smallest Δ VOT values) in the region of the phonetic boundary dividing voiceless‐unaspirated and voiceless‐aspirated sounds, in good agreement with the boundary value previously obtained in an identification task with this same species [Kuhl and Miller, J. Acoust. Soc. Am. 63, 905 (1978)]. The results support the notion that the mammalian auditory system provided a selective pressure on the choice of acoustic cues to represent the phonetic oppositions employed by the world’s languages. The data are discussed in terms of the original definition of categorical perception and ...

Effects of frequency-shifted feedback on the pitch of vocal productions.

Abstract: Previous investigations into the effects of distorted auditory feedback on vocalizations have been limited to manipulations of intensity, background noise, temporal delay, or to selective filtering of frequency. The current study reports the results of real‐time shifts of the frequency components of auditory feedback. Subjectively, such shifts are perceived primarily as an alteration in the fundamental frequency (F0) of the speech. Subjects performed a variety of tasks under conditions where they received either normal auditory feedback or frequency‐shifted feedback. Under normal feedback conditions, subjects maintained approximately constant F0 as instructed. With frequency‐shifted feedback, subjects attempted to compensate for the shift by adjusting their F0 up or down such that the resulting feedback appeared to be ’’normal.’’

Linguistic timing factors in combination

Abstract: This study attempts to determine the ways in which linguistic timing factors combine with each other in the production of English and specifically, to test and explore aspects of the timing model of Klatt [J. Acoust. Soc. Am. 59, 1208–1221 (1976)]. In two experiments the tensity feature of a sentence stressed vowel and the voicing of the following stop were changed along with a variable that alters the length of the VC syllable. The duration of both the vowel, V, and the following stop closure, C, were measured. In the first experiment either one or two unstressed syllables are added to the word and in the second speaking tempo is changed. The significant results of both experiments are accounted for with a formal timing model that separately specifies (1) the Vm+C duration (where Vm= mean duration across the two vowels /i/ and /i/) depending on tempo or word length, (2) the ratio Vm/C depending on the voicing of the stop (/b/ or /p/), and (3) as a final ordered step, a rule that adjusts the vowel length by a constant ratio depending on the identity of the vowel. This integrated model provides for (1) the ’’incompressibility’’ effects, (2) prosodic properties, and (3) the constant V/C ratios for values of the voicing feature found in perception experiments.

Computer‐generated pulse signal applied for sound measurement

Abstract: A computer‐generated pulse signal for sound measurement is discussed. A pulse signal whose power spectrum is flat is generated by inverse Fourier transformation. The generation of a time‐stretched pulse and its compression method are also discussed. Computer‐controlled measurements enable time averaging and the elimination of reflected sound is made in the computer memory by the operator’s instruction monitoring acquired waveform on CRT.

Perceptual dimension of openness in vowels.

Abstract: The role of intrinsic factors determining perceived degree of vowel openness was examined. In order to determine the role of F1 and F0, one‐formant vowels, covering a wide range of fundamental and formant frequencies, were identified by 23 subjects who were native speakers of a Bavarian dialect in which five degrees of openness occur distinctively. The significance of intrinsic factors other than F1 and F0 was also studied using synthetic versions of natural vowels with F1 and/or F0 systematically displaced in frequency. It was found that, generally, the tonality distance between F1 and F0 is decisive for openness, while the higher formants contribute marginally. It was further found that the distance between widely spaced formants, as between F2 and F1 in front vowels, is not crucial for vowel identification. The results are evaluated in terms of a psychoacoustic model of identification by pattern matching. The model incorporates two basic assumptions. First, a certain pattern of excitation along the basilar membrane is recognized as a given feature regardless of position along the membrane. Second, there is an integration band with a width of 3 Bark effective in spectrum envelope recognition.

Modeling the judgment of vowel quality differences

Abstract: The hypothesis of this study is that the auditory cues relevant to listeners’ judgment of vowel quality are a spectral representation of loudness density versus pitch. A model is described that generates such patterns for steady‐state vowels. In addition to the nonlinear transformations underlying the loudness density and pitch scales, it incorporates experimentally established characteristics associated with frequency resolution and masking, such as the critical band concept. This model is combined with a measure of auditory perceptual distance which, operating on pairs of vowels, treats each stimulus representation as a single spectral shape. In order to test the distance metric and the model, experimental data were gathered from listeners’ numerical estimates of quality differences between stimulus pairs which compared four‐formant and two‐formant vowels. The correlation between experimental and theoretical results was 0.89. We interpret this value to indicate that the present definition of auditory cue and auditory distance can be said to account for the experimental behavior of our listeners only in a rather gross fashion. On the other hand, the theory was developed on the basis of rather conservative assumptions about the nature of auditory cues. For instance, the model ignores the possibility of temporal coding and certain nonlinear effects, and it does not pay special attention to spectral peaks. Seen in that light, the agreement between observed and predicted auditory distance is remarkably good.

Influence of preceding fricative on stop consonant perception

Abstract: The effect of a preceding fricative on the perceived place of stop consonant articulation was investigated in a series of experiments. In experiment 1, we preceded synthetic syllables from two [tV]–[kV] continua with fricative noises appropriate to [F] or [s] and showed that more velar stops are perceived in the context of [s]. Experiment 1 also demonstrated a decrease in the magnitude of this perceptual context effect with increased temporal separation of fricative noise and CV portion, and with introduction of a vowel before the noise, which permitted a subjective syllable boundary after the fricative. Experiment 2 showed that although the effect of the fricative on stop perception declines initially with temporal separation, it may persist in reduced form over intervals as long as 375 ms. Experiment 3 replicated the basic fricative context effect using improved stimuli, but failed to replicate the reduction with an intervening syllable boundary obtained in experiment 1, which presumably was due to the ...

Heat generation by ultrasound in a relaxing medium

Abstract: It is shown that at any point P in a continuous sound field the time‐averaged rate of heat generation by relaxational absorption per unit volume is given by αp02/ρc. Here p0 is the pressure amplitude at P while α is the absorption coefficient arising from relaxation when the coefficient of shear viscosity η is zero; ρ and c are, respectively, the density and velocity of sound in the medium. The result, a familiar one for plane traveling waves, is shown here to apply generally when η = 0.

Method for determining the extent of subsurface reaction involving acoustic signals

Abstract: A method determines the extent of subsurface reactions in which random acoustic signals are radiated from a whole area covered by the reaction or from a boundary region, hereafter termed reaction front, between largely undisturbed rocks and those already covered by the reaction. The signals are recorded by at least two receivers positioned at different locations outside the reaction area. The recorded signals are cross-correlated as a function of a time shift between the recorded signals so that at least one surface confining the reaction area is determined from the cross-correlation.

Played-again SAM: Further observations on the pitch of amplitude-modulated noise

Abstract: The pitchlike sensation elicited by sinusoidally amplitude‐modulated (SAM) noise remains a controversial phenomenon. The controversy centers on two major points: (1) whether this sensation is ’’really’’ pitch rather than, e.g., roughness or intermittency, and (2) the possibility that any pitch sensation is mediated by short‐term spectral information rather than temporal information—thus nullifying an interesting aspect of the phenomenon. Three experiments employing SAM wideband noise, SAM wideband noise bandpass‐filtered after modulation, and a SAM 10 kHz pure tone were performed: (1) open‐set melody identification, (2) melodic dictation, and (3) musical‐interval adjustment. These experiments extend our earlier study [Burns and Viemeister, J. Acoust. Soc. Am. 60, 863 (1976)]. The results provide further evidence that SAM noise can, at suitable modulation frequencies, elicit a sensation of pitch (as defined by the ability to carry melodic information), and that this pitch represents a purely temporal phenomenon.

A reconsideration of acoustic invariance for place of articulation in diffuse stop consonants: Evidence from a cross‐language study

Abstract: This study explored the claim that invariant acoustic properties corresponding to phonetic features generalize across languages. Experiment I examined whether the same invariant properties can characterize diffuse stop consonants in Malayalam, French, and English. Results showed that, contrary to theoretical predictions, we could not distinguish labials from dentals, nor could we classify dentals and alveolars together in terms of the same invariant properties. We developed an alternative metric based on the change in the distribution of spectral energy from the burst onset to the onset of voicing. This metric classified over 91% of the stops in Malayalam, French, and English. In experiment II, we investigated whether the invariant properties defined by the metric are used by English‐speaking listeners in making phonetic decisions for place of articulation. Prototype CV syllables—[b d] in the context of [i e a o u]—were synthesized. The gross shape of the spectrum was manipulated first at the burst onset, then at the onset of voicing, such that the stimulus configuration had the spectral properties prescribed by our metric for labial and dental consonants, while the formant frequencies and transitions were appropriate to the contrasting place of articulation. Results of identification tests showed that listeners were able to perceive place of articulation as a function of the relative distribution of spectral energy specified by the metric.

Forward and backward projection of acoustic fields using FFT methods

Abstract: The forward and backward propagation of harmonic acoustic fields using Fourier transform methods is presented. In particular, the forward propagation of a velocity distribution to obtain a pressure field and the backward propagation of a pressure field to obtain a velocity distribution are addressed. Numerical examples are presented to illustrate the nearfield behavior of the pressure field from complex planar vibrators, e.g,—an ultrasonic transducer or plate, with nonuniform velocity distributions. The numerical results, which were obtained via the use of FFT algorithms, are presented for vibrators which are operating above and below coincidence. These results illustrate the acoustic nearfield as a function of distance from the vibrator. Numerical results are also presented to illustrate the backward projection method. The pressure field of a 3×3 focused array is back projected to obtain the velocity distribution for several cases of interest. These results illustrate the utility of the transform method and the effect of spatial windows or filters in its implementation using FFT algorithms.

Differential sensitivity to pitch distance, particularly in speech.

Abstract: The fundamental frequency in speech shows many rapid variations, part of which determine the perceived shape of the pitch contour. This implies that the accuracy with which listeners perceive changes of F0 is more relevant to understanding the perception of intonation than the traditional just noticeable difference of F0 in speech. This study examines the sensitivity to differences in the amount of change of F0, upward (Experiment Ia) and downward (Experiment Ib). Subjects, 74 and 104, respectively, with widely different musical ability can be divided into three categories: (1) Quite a number of them were not able to discriminate differences of less than 4 semitones (nondiscriminators); (2) other subjects wrongly tried to base their judgments on a simple comparison of the final pitches of a stimulus pair (final pitch discriminators); (3) the remaining subjects (pitch distance discriminators) yielded average jnd’s of about 1.5 to 2 semitones. Since the issue is associated with musical interval sense, simil...

Ultrasonic attenuation and propagation speed in normal human brain

Abstract: Attenuation and propagation speed in the 1‐ to 5‐MHz frequency range were measured in vitro in 22 tissue samples from six anatomic sites in five normal human brains obtained unfixed at autopsy. Two methods were used to measure attenuation: (1) received amplitude reduction resulting from insertion of tissue sample between a pair of transducers, and (2) radiation force reduction resulting from insertion of tissue sample between a transducer and a reflector. The piezoelectric transducer method gave attenuation values −10% to +90% higher than the radiation force method. Attenuation (by transducer method) was a function of frequency to the 1.08 power with a value of 0.87 dB ⋅ cm−1 at 1 MHz. Propagation speed was measured by observing signal arrival time change resulting from insertion of the tissue sample between the transducer pair. Propagation speed was 1562 m ⋅ s−1 at 1 MHz with a dispersion of 1.2 m ⋅ s−1 ⋅ MHz−1 over the 1‐ to 5‐MHz frequency range. Ages at death were 3 days, 20, 21, 42, and 72 years. R...

Study of multichannel amplitude compression and linear amplification for persons with sensorineural hearing loss

Abstract: Experiments were conducted on five listeners with sensorineural hearing impairments using two 16‐channel, computer‐controlled, amplitude compression systems, and four linear systems. One of the compression systems was designed to restore normal equal loudness contours, the other employed reduced high‐frequency emphasis and reduced compression ratios. The linear systems differed only in their frequency‐gain characteristics (orthotelephonic plus three characteristics with high‐frequency emphasis that were expected to produce better results than orthotelephonic). In the main experiment, all systems were compared for each listener using nonsense CVC monosyllables and sentence materials spoken by male and female talkers and presented in quiet/anechoic and noisy/reverberant environments at the most comfortable level for each listener. The linear systems with high‐frequency emphasis performed substantially better than the orthotelephonic system. Performance with compression was generally slightly worse than with linear amplification. Compression was superior to linear amplification only when speech materials with significant item‐to‐item level variation were used in quiet with subjects with more severe losses and when reduced input speech levels were used. To the extent that these two conditions represent real‐life communication conditions, these results suggest that compression is preferable to linear amplification in a wearable hearing aid.

Second formants in fricatives: Acoustic consequences of fricative‐vowel coarticulation

Abstract: Spectral analyses of the sibilant fricatives, [s, z, F, z], as spoken in isolation and in initial position before the vowels [a, i, u], were performed for a corpus of 80 utterances. The mean LPC spectra for five utterances of each fricative produced in each vowel context revealed reliable anticipatory vowel coarticulation effects present at least 30–60 ms before vowel onset in the form of spectral peaks affiliated with the second formant of the vowel. Peak frequencies were between 1.5 and 2 kHz and were approximately 100–300 Hz higher before the front vowel [i] than before the back vowels [a, u]. The presence of these peaks in the fricative spectra indicate that during the latter part of the fricative the constriction begins to open in anticipation of the vowel, and, as a consequence, second formant resonances are excited. The acoustic characteristics of these fricative formants varied as a function of vowel context due to differences in the anticipatory coarticulation of the vowel. Fricative place of con...

Elastic wave propagation in fluid‐saturated porous media II

Abstract: Recently, a new method of deriving the coefficients in the strain energy functional of Biot’s theory for elastic waves in fluid‐saturated porous media was proposed. The results of this approach have been criticized as being unphysical in the limit K*/Kf → 0, where K* and Kf are the frame and fluid bulk moduli. We show that an error arose due to the literal interpretation of the term ef as the fluid dilatation whereas this term actually differs substantially from the fluid dilatation in some situations. We also show that by lumping part of the solid together with the fluid (conceptually) to form a fictitious fluid suspension, the corresponding fictitious ef may be correctly interpreted as the dilatation of the fluid suspension. This trick leads to a transformation which takes the recently published formulas into standard form. The standard formulas are found to be invariant under the same transformation. New insight into the significance of the standard formulas for the coefficients is obtained.

An excitation‐pattern model for intensity discrimination

Abstract: This paper evaluates two different versions of Zwicker [Acustica 6, 365–381 (1956)] and Maiwald’s [Acustica 18, 193–207 (1967)] excitation‐pattern model for intensity discrimination. The single‐band version is that originally used by Zwicker and Maiwald. They assumed that performance was determined by the critical band in which the excitation grows most rapidly with increasing level of the stimulus. The multiband version forms an optimum decision based on information in all critical bands. Predictions from the two versions of the model are compared to data for intensity discrimination of tones as a function of level and frequency, for partially masked tones and for white noise. In general, the single‐band version yields predictions in qualitative agreement, but not in quantitative agreement with the intensity‐resolution data for pulsed tones. The multiband version yields predictions in good qualitative as well as quantitative agreement with the data, except at high frequencies.

Interaural correlation discrimination: i. bandwidth and level dependence

Abstract: Measurements of interaural cross‐correlation jnds from two reference correlations at several bandwidths were obtained for constant‐total‐power and constant‐spectral‐power Gaussian noise. At a reference correlation of 1, the results indicate that for bandwidths less than or equal to 115 Hz the jnd remains at a constant value of approximately 0.004, and monotonically increases (discrimination performance degrades) to approximately 0.04 as bandwidth increases above 115 Hz. At a reference correlation of 0, the jnd decreases (discrimination performance improves) from approximately 0.7 to 0.35 as the bandwidth increases from 3 to 115 Hz, and remains at a constant value of approximately 0.35 for bandwidths greater than 115 Hz. A decrease in the spectral level causes an increase in the jnds at a reference correlation of 1, and no change in the jnds at a reference correlation of 0. Of the three models tested, none is able to completely describe all of the empirical results.