摘要:

Findings are described from three experiments that were designed to contrast estimates of auditory time and frequency analysis in highly practiced, young adult subjects having sensorineural hearing loss of cochlear origin with subjects having normal hearing. In one experiment, pure‐tone detection threshold was measured for two durations of tones. For the hearing‐impaired subjects, smaller differences were found between thresholds for the two durations of tones than were found for the normally hearing subjects at test frequencies where the sensitivity loss was greatest. In a subsequent forward masking experiment, masked thresholds were obtained at 3 kHz as a function of masker level at several masker durations. The results indicated that, for the range of values tested, masked probe thresholds changed less as a function of masker duration for the hearing‐impaired subjects than for normally hearing subjects. However, forward masking grew as a function of masker level more steeply for the hearing‐impaired listeners than for the normally hearing listeners. We believe that this result indicates abnormal temporal processing of sequential sounds. In a third experiment, psychophysical tuning curves were measured in a forward masking procedure for two maskers that differed in duration by approximately an order of magnitude. Again, the hearing‐impaired subjects demonstrated less change in forward masking as a function of masker duration than normally hearing subjects. Further, the sharpness of the tuning curves from the hearing‐impaired listeners was markedly reduced as compared to normal. It is believed that the results reflect a disruption of the normal temporal and spectral representation of sounds in the hearing‐impaired subjects.

ISSN:0001-4966    

DOI:10.1121/1.390558

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

A previous study of mandible movements in normal speech [W. L. Nelson, J. Acoust. Soc. Am. Suppl. 168, S32 (1980)] suggested that the speech motor control process resulted in a relationship between movement time, distance, and peak velocity which implied (1) some adaptation to the physical effort required for the movement, and (2) that the force limit effective during speech was considerably below that which the mandibular muscles are capable of producing. In the present study, mandible movements were measured during maximally rapid opening and closing tasks, and during increasingly rapid repetitions of a spoken syllable and a nonspeech ‘‘syllable.’’ The results indicate that (1) peak acceleration levels for the repeated mandible movements were less than half of those for the maximally rapid single mandible movements, and (2) a rather different mode of control is used for the repeated speech movements as compared to the nonspeech movements.

ISSN:0001-4966    

DOI:10.1121/1.390559

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

We studied listeners’ intonation sensitivity to traditional (major and minor) and nontraditional chords. The nontraditional chords have frequency ratios of 3:5:7 and 5:7:9 and, like the major chord, have coincident upper partials and unambiguous fundamental basses. The center tone only of each of these four triads was varied from its just (integer ratio) value by −30, −15, 0, +15, and +30 cents. Each tone had ten partials whose amplitudes decreased with frequency relative to the fundamental (9 dB per octave). Subjects judged which chord (or chordal sequence) of a pair was more in tune, smooth and/or pleasant. Listeners’ intonation sensitivity curves exhibited regular patterns for both traditional and nontraditional chords. However, our subjects divided into two groups: One group preferred chords in just intonation and their preferences decreased monotonically as the intonation deviated from just intonation; the other group preferred intonations that deviated from just intonation by ±15 cents.

ISSN:0001-4966    

DOI:10.1121/1.390560

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Ultrasonic absorption values in aqueous solutions of myoglobin, apomyoglobin, α‐lactalbumin, bacitracin, and the C‐ and N‐terminal CNBr cleavage fragments of myoglobin were determined by the cylindrical resonator technique at temperatures of 4 °C and 20 °C in the frequency range 0.5–7 MHz. A proposed mechanism of absorption in solutions of proteins and peptides is perturbation by the ultrasound of the equilibrium between protein bound and free water, producing a distribution of relaxation processes occurring within the frequency range of the investigation. The hypothesis is supported by the dependence of the ultrasonic absorption on solute surface area and molecular weight. Another mechanism of absorption is that due to proton transfer which occurs noticeably in the presence of phosphate ions. Those proteins (myoglobin and α‐lactalbumin) with significant globular structure appear to undergo additional relaxation processes at frequencies above 7 MHz.

ISSN:0001-4966    

DOI:10.1121/1.390561

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

This paper describes the theory of the interchange reference method for the precise assessment of phase difference θ and amplitude ratioRof two coherent sinusoidal signals. Systematic errors are analyzed in depth. For θ equal to 10°, the uncertainties inRand θ are of the order of 2 ppm and less than 0.01°, respectively. Experimental verification confirms the theory of the above method.

ISSN:0001-4966    

DOI:10.1121/1.390562

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

This paper reviews a technique for the generation of broadband acoustic transmissions. Wiener (least‐squares) filtering is applied to the problem of precompensating the transducer driving waveform so that the subsequent acoustic pulse has a broadband nature. Experimental results show that a transducer having two resonance peaks at 9 and 17 kHz, each having bandwidths of about 2.5 kHz, may be compensated to have less than 3.5‐dB ripple in the transmitting frequency response from 7 to 37 kHz.

ISSN:0001-4966    

DOI:10.1121/1.390563

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

The behavior of an edge‐supported circular membrane foil electret earphone is studied in a three‐step analytical procedure. First, the static deflection is determined for a specified set of transducer parameters. The deflection is expressed as a power series in radial location. Second, the dynamic deflection, which depends on the static deflection, is found. It is also expressed as a power series in radial location. Third, the linear dynamic response is examined to determine a procedure for maximizing the sound pressure level which is generated in the ear. The results presented here indicate that with the choice of an optimum set of earphone parameters it is possible to construct an earphone with a sensitivity of 82 dB/V and a relative distortion level of about −40 dB.

ISSN:0001-4966    

DOI:10.1121/1.390564

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

This paper presents experimental measurements of the static and dynamic behavior of an edge‐supported circular membrane electret earphone. It is shown that the measured value of static capacitance and sound pressure level generated in a cavity agree well with theoretical predictions. The experimental results dramatize the nonlinear dependence of the earphone sensitivity on many of the transducer parameters. The effects of fluid loading of the foil electret and damping are considered. It is shown that the air surrounding the foil electret can significantly increase its apparent mass, and that damping effects may be ignored below the system fundamental resonance.

ISSN:0001-4966    

DOI:10.1121/1.390565

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

The basic equation for plane elastic waves in crystals remains invariant under a reversal of the propagation direction. If the direction of the wave normal is rotated in a crystallographic plane containing an acoustic axis, a situation may arise under certain conditions which leads to an apparent violation of this inversion symmetry, namely, to a period of 360° for the angular dependence of phase velocity and displacement eigenvectors of both quasitransverse modes. A specific example for this is given and the general conditions for the occurrence of this situation are discussed.

ISSN:0001-4966    

DOI:10.1121/1.390566

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

We have reported earlier the observation of backscattered leaky Raleigh waves from a liquid–solid interface [J. Acoust. Soc. Am.72, 1018–1020 (1982)]. Now we have carried out experiments to observe backscattered leaky Lamb waves from a plate immersed in liquid, using a single transducer in pulse echo modes. Sharp peaks were observed at angles corresponding to backward propagating symmetrical and antisymmetrical Lamb modes. These backward propagating Lamb waves leak back at both sides of the plate.

ISSN:0001-4966    

DOI:10.1121/1.390567

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP