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Journal of the Acoustical Society of America

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Dec 1970

Volume 48, Issue 6B, pp. 1355-1432


Two Experiments on Pitch Perception: Diplacusis of Harmonic AM Signals and Pitch of Inharmonic AM Signals

G. van den Brink

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1355-1365 (1970); (11 pages) | Cited 2 times

Online Publication Date: 03 Aug 2005

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In the first experiment, binaural diplacusis for harmonic three‐component (amplitude‐modulated signals has been measured. There appears to be a good agreement between diplacusis for complex signals and the average of the pure‐tone diplacusis for its spectral components. In all cases, the pitch of the stimuli used roughly agreed with the pitch of the common, but nonexistant, fundamental. Apparently, the pitch of the separate components is more important than their frequency. Conclusively, the origin of binaural diplacusis cannot be found in a peripherally located mechanism, but in some higher center. In the second experiment, the pitches of inharmonic amplitude‐modulated signals were matched monaurally with those of harmonic signals. The experiment gives direct quantitative information of the pitch deviations which have been found regarding the time‐fine‐structure theory. These deviations increase progressively with the rate of inharmonicity of the signal and decrease with decreasing intensity and modulation depth. The results suggest that the deviations are due to neural interaction mechanisms and thus can not be described in simple mathematical formulas.

Earmold Alteration Effects as Measured in the Human Auditory Meatus

F. Douglas McDonald and Gerald A. Studebaker

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1366-1372 (1970); (7 pages)

Online Publication Date: 03 Aug 2005

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Human ears were utilized to examine the effects of change in earmold form upon sound‐pressure levels in the ear canal at selected discrete frequencies from 0.1 to 4 kHz. Four earmolds were fabricated for each of eight subjects. One retained an unaltered form for the purpose of comparison, while the other three were modified, respectively, to a shortened canal form, a shortened canal form which was vented, and an open form. Measurements were made utilizing a probe‐tube microphone assembly. Relative to the unaltered earmold form, the shortened canal modification caused a slight reduction for all frequencies except 3 and 4 kHz, while the vented and open forms produced marked reductions in low‐frequency response accompanied by large resonances. Certain relevant measurements made using a standard 2‐cm3 a coupler and a special 2‐cm3 coupler are also presented.

A Model for Two‐Tone Inhibition of Single Cochlear‐Nerve Fibers

Russell R. Pfeiffer

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1373-1378 (1970); (6 pages) | Cited 10 times

Online Publication Date: 03 Aug 2005

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An analog model by Engebretson and Eldredge accounts for nonlinear properties of the cochlear microphonic (CM) in response to single‐ and two‐tone stimulation. Recent evidence that shows strong similarities between CM and spike‐discharge patterns of single cochlear‐nerve fibers has prompted an association of two‐tone interaction of CM with two‐tone inhibition of nerve fibers, leading to a modification of the model for CM so as to make it applicable to cochlear‐nerve fibers. The result is a model that has clear two‐tone inhibition properties similar to those observed experimentally. Mathematical analysis applied to the model shows that the “inhibition” is easily explained by signal suppressions inherent to bandpass nonlinearities.

Degrees of Freedom of Cochlear Patterns

R. E. Rink

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1379-1382 (1970); (4 pages)

Online Publication Date: 03 Aug 2005

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Although auditory patterns, from the cochlea inwards, are distributed in space and time, they do not have an infinite number of degrees of freedom. Because of mechanical coupling, motions at neighboring points along the cochlea are not statistically independent. Results are given for the number of equivalent degrees of freedom along the spatial axis of auditory patterns when displacement of the basilar membrane is the pattern variable and when envelope of displacement is the pattern variable. These numbers are compared with other estimates of the dimensionality of auditory pattern space.

Auditory Memory in a Pitch‐Discrimination Task

Ian B. Thomas, Paul D. Dinicola, Michael P. Ella, and Carl S. Pasierbiak

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1383-1386 (1970); (4 pages)

Online Publication Date: 03 Aug 2005

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Discrimination of pure tones after a variable time delay was investigated using an ABX procedure. Three experiments were performed. In the first, scores for subjects were near perfect (>90%) for systematically increasing delays between B and X of up to 120 sec when A and B were equal‐amplitude pure tones of 1000 and 1100 Hz, respectively. In the second and third experiments, three tone pairs were employed having frequency spacings of 10% and 2%, respectively. The pair used, the order within pairs, and the order in which variable delays were presented were all randomized. In these experiments, scores fell abruptly after a delay of 20 sec for the 10% spacing and after 5 sec for the 2% spacing. The superior discrimination of Expt. 1 is attributed to learning.

Audiometer‐Earphone Mounting to Improve Intersubject and Cushion‐Fit Reliability

Edgar Villchur

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1387-1396 (1970); (10 pages)

Online Publication Date: 03 Aug 2005

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The range of combined intersubject and cushion‐fit variation in the response of the TDH‐39 audiometer earphone in an MX41/AR cushion, reported in the literature and confirmed in these measurements, is of the order of 25 dB at 100 Hz, 6 dB at 1 kHz, and 15 dB at 5 kHz. The performance of this earphone system is further impaired by cushion‐induced physiological noise that masks low‐frequency thresholds, typically by 6 dB in normal‐hearing subjects. An experimental mounting for the TDH‐39 is described and analyzed; it is a circumaural device designed to keep the earphone‐ear acoustical system as near constant as possible with successive fittings and different subjects, and to reduce physiological noise. The performance of the TDH‐39 in this mounting, compared to performance in an MX41/AR cushion, showed a substantial reduction in cushion‐fit and intersubject response variation, and masking by physiological noise was largely eliminated in the subjects tested. The mounting has an optional cup for reducing the transmission of external noise, but this reduction is at the expense of a partial return of physiological noise masking. Average midrange sensitivity was reduced 5–6 dB. Response measurements were made with a free‐field reference method, using a probe microphone at the subject's eardrum.

Elimination of Biases in Loudness Judgments for Tones

Richard M. Warren

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1397-1403 (1970); (7 pages)

Online Publication Date: 03 Aug 2005

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Loudness judgments are especially sensitive to experimentally induced biases. By using a method derived from studies of visual intensity, it was found possible to obtain loudness estimates free from known biasing factors. Judgments of 50% loudness corresponded to 25% stimulus intensity (6‐dB attenuation) for 1000‐Hz tones from 42 through 92 dB, and for tones from 250 through 8000 Hz presented at moderate intensity. These results agree with other data supporting the physical correlate theory of sensory intensity. It is suggested that the sone scale of loudness reflects the influence of known experimental biases and hence does not represent a fundamental relation between stimulus and sensation.

Formant Concentration Positions in the Speech of Children at Two Levels of Linguistic Development

John H. Gilbert

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1404-1406 (1970); (3 pages)

Online Publication Date: 03 Aug 2005

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This investigation was concerned with acoustic measurements of the first two formants in four sustained vowels—/i/, /æ/, /a/, and /u/—produced by children at two different levels of linguistic development. The object of the investigation was to determine whether children of the same chronological age but at a different level of language development would exhibit significant differences of formant frequencies. Acoustic measurements of formants 1 and 2 of the four sustained vowels /i/,/æ/,/a/, and /u/ showed no statistically significant differences when produced by two groups of children at two levels of linguistic development. In each group, differences among formant measurements, for the four vowels, were significantly different.

Aids in Ultrasonic Diagnosis

G. Baum

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1407-1412 (1970); (6 pages)

Online Publication Date: 03 Aug 2005

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This paper describes three new types of displays for use in medical ultrasonography. These are video inversion, scanned deflection modulation, and scanned deflection‐intensity modulation. Video inversion is a B‐mode display in which the ultrasonographic data is presented as a radar and TV display on alternate scans. This display makes it possible to use the steep slope of the gray scale on the face of the cathode‐ray tube to display small changes in amplitude in both the very loud and weak ends of the acoustic spectrum. Scanned deflection modulation or scanning A‐mode restores anatomical orientation. This type of display greatly facilitates interpretation of medical ultrasonograms. Scanned deflection modulation has been combined with intensity modulation to produce scanned deflection‐intensity modulated ultrasonograms. This form of ultrasonographic data displays greatly facilitates ultrasonographic localization.

Threshold Ultrasonic Dosages for Structural Changes in the Mammalian Brain

F. J. Fry, G. Kossoff, R. C. Eggleton, and F. Dunn

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1413-1417 (1970); (5 pages) | Cited 9 times

Online Publication Date: 03 Aug 2005

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The relationship between the acoustic intensity and the time duration of exposure, for a single pulse, necessary to produce a threshold lesion in the cat brain was studied. Focused ultrasound of 1, 3, and 4 MHz was employed with intensities ranging from 102 to 2×104 W/cm2 with the corresponding pulse durations from 7 to 2×10−4 sec, respectively. Three types of lesions were observed attending three regions. At the lower intensities and long time durations of exposure, the lesion is produced by a thermal mechanism. At the highest intensities and shortest time durations, cavitation is believed to be the mechanism responsible for the sometimes randomly appearing lesions. At intermediate dosages, the lesions are formed by a mechanical mechanism which is thus far not well understood. These results exhibit good agreement with that of other investigators on both the cat and the rat brain.

Sound Conduction in the Dolphin Ear

Jamers G. McCormick, Ernest Glen Wever, Jerry Palin, and Sam H. Ridgway

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1418-1428 (1970); (11 pages) | Cited 8 times

Online Publication Date: 03 Aug 2005

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By use of the electrical potentials of the cochlea, the pathway of sound conduction to the ear was investigated in two species of dolphins, Tursiops truncatus and Lagenorkynchus obliquidens. The observations show that the external auditory meatus is vestigial and that neither this meatus nor the tympanic membrane plays any part in sound reception. The ossicular chain has an essential function, though the outermost ossicle, the malleus, can be removed without seriously affecting the conductive process. It is concluded that auditory stimulation in the dolphin occurs by bone conduction. Acoustic vibrations in the water reach the ear through the tissues of the head, and set up differential motions between the stapes and the cochlear capsule. These differential motions involve the cochlear fluids, which are given mobility by the presence of gas in the region of the round window. The vibrations of the basilar membrane and stimulation of the hair cells of the organ of Corti then follow in the usual way.
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Validation of the Single‐Impulse Correction Factor of the CHABA Impulse‐Noise Damage‐Risk Criterion

David C. Hodge and Georges R. Garinther

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1429-1430 (1970); (2 pages) | Cited 1 time

Online Publication Date: 03 Aug 2005

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Seventy‐six subjects were exposed to single impulse noises produced by two small shoulder‐fired rockets, and TTS2 was compared with the CHABA limits. The single impulse, 95% protection, and grazing incidence correction factors of the CHABA damage‐risk criterion were validated. Grazing‐incidence shock waves produced comparable results when they arrived at the ear from the front and from the rear.

Acoustical Beam Patterns for Bats: Some Theoretical Considerations

G. K. Strother and M. Mogus

J. Acoust. Soc. Am. Volume 48, Issue 6B, pp. 1430-1432 (1970); (3 pages) | Cited 3 times

Online Publication Date: 03 Aug 2005

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Acoustical beam patterns for emission from several different bats are calculated assuming a piston source in an infinite baffle, both as single and as double emitters. The calculated beam patterns agree well enough with experimental values available in the literature to justify the assumptions used. For those bats which possess no facial appendages to serve as a baffle, the simple acoustical model does not work, as anticipated. The calculated beam patterns are for fixed frequencies in the examples used; however, some aspects of frequency modulated beams are briefly discussed.
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