摘要:

The determination of an acoustical impedance requires measurements of pressure and volume velocity. As no direct method is available for measuring velocity in an ear canal, a technique was developed which is based on pure pressure measurements. The ear canal is used as a measuring tube, the area function of which is also deduced from the pressure measurements. High‐frequency measurements in living subjects involve many sources of errors. A criterion for deciding if a good measurement has been made is given. The technique of measurements is described, regarding both the use of probe tube microphones and the computer aided data recording. Finally, the results are presented, and some comments are given. A reliable interpretation of the results seems to be impossible because of lack of our knowledge of the middle ear function at high frequencies.

ISSN:0001-4966    

DOI:10.1121/1.388855

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

This study investigates the controversy regarding the influence of age on the acoustic reflex threshold for broadband noise, 500‐, 1000‐, 2000‐, and 4000‐Hz activators between Jergeretal. [Mono. Contemp. Audiol.1(1978)] and Jerger [J. Acoust. Soc. Am.66(1979)] on the one hand and Silman [J. Acoust. Soc. Am.66(1979)] and others on the other. The acoustic reflex thresholds for broadband noise, 500‐, 1000‐, 2000‐, and 4000‐Hz activators were evaluated under two measurement conditions. Seventy‐two normal‐hearing ears were drawn from 72 subjects ranging in age from 20–69 years. The results revealed that age was correlated with the acoustic reflex threshold for BBN activator but not for any of the tonal activators; the correlation was stronger under the 1‐dB than under the 5‐dB measurement condition. Also, the mean acoustic reflex thresholds for broadband noise activator were essentially similar to those reported by Jergeretal. (1978) but differed from those obtained in this study under the 1‐dB measurement condition.

ISSN:0001-4966    

DOI:10.1121/1.388856

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Probe‐elicited wave V amplitudes of the auditory brainstem response (ABR) were measured using a forward‐masking paradigm. Subjects were anesthetized cats. For individual experiments, probe frequency and intensity were fixed and masker frequencies and intensities were varied. For each masker frequency, the extent to which the probe‐elicited wave V amplitude was reduced by the preceding masker was plotted as a function of masker intensity. The rising segments of the masking functions were fitted with straight lines, using a least‐squares procedure, to obtain estimates of their slopes. Masking grew most rapidly for masker frequencies below probe frequency, becoming progressively less steep as masker frequency increased. ABR tuning curves were constructed by using the linear fits to define the masker intensity that caused a 50% reduction in probe‐elicited wave V amplitude. The shapes of these tuning curves were comparable to whole‐nerve action potential (AP) tuning curves obtained under similar stimulus conditions. These results indicate that ABR amplitude measurements in a forward‐masking paradigm can be used to estimate the growth of response to masking stimuli and frequency selectivity in a manner similar to AP amplitude measurments.

ISSN:0001-4966    

DOI:10.1121/1.388858

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Simultaneous masking functions (signal level at threshold versus masker level) were obtained for equally intense maskers presented individually and in pairs. The signal was a 2.0‐kHz sinusoid. The pairs of maskers were (1) two sinusoids with frequencies 1.9 and 2.1 kHz, (2) two narrow bands of noise (50 Hz wide) centered at 1.9 and 2.1 kHz, (3) two narrow bands of noise (50 Hz wide) centered at 1.8 and 1.9 kHz, and (4) the 1.9‐kHz sinusoid combined with the narrow band of noise centered at 2.1 kHz. The pairs of maskers produced anywhere from 10 to 17 dB of masking beyond that predicted from the simple sum of the masking produced by the individual maskers. The amount of this ‘‘additional masking’’ was independent of masker level. Adding a continuous low level background noise reduced the amount of additional masking only slightly (approximately 5 dB). The data are consistent with a model in which the effects of the maskers are summed after undergoing independent compressive transformations.

ISSN:0001-4966    

DOI:10.1121/1.388859

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Simultaneous psychophysical tuning curves were obtained from normal‐hearing and hearing‐impaired listeners, using probe tones that were either at similar sound pressure levels or at similar sensation levels for the two types of listeners. Tuning curves from the hearing‐impaired listeners were flat, erratic, broad, and/or inverted, depending upon the frequency region of the probe tone and the frequency characteristics of the hearing loss. Tuning curves from the normal‐hearing listeners at low‐SPL’s were sharp as expected; tuning curves at high‐SPL’s were discontinuous. An analysis of high‐SPL tuning curves suggests that tuning curves from normal‐hearing listeners reflect low‐pass filter characteristics instead of the sharp bandpass filter characteristics seen with low‐SPL probe tones. Tuning curves from hearing‐impaired listeners at high‐SPL probe levels appear to reflect similar low‐pass filter characteristics, but with much more gradual high‐frequency slopes than in the normal ear. This appeared as abnormal downward spread of masking. Relatively good temporal resolution and broader tuning mechanisms were proposed to explain inverted tuning curves in the hearing‐impaired listeners.

ISSN:0001-4966    

DOI:10.1121/1.388860

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Identification experiments using 13 tone‐pulse stimuli (1000 Hz, 500 ms) spaced by equal decibel increments from 42 to 90 dB SPL were conducted under three conditions: all intensities equally likely (denoted Q), the middle intensity presented on roughly 1/3 of the trials (M), and each of the extreme intensities presented on roughly 1/5 of the trials (E). Experiments were performed both with and without feedback, and results were analyzed in terms of sensitivity and bias. Similar results were obtained with and without feedback: listeners generally shifted biases in the M and E conditions relative to the Q condition to increase percent‐correct scores, but there were only minor changes in sensitivity from condition to condition. However, sensitivities were generally higher and biases more optimal when feedback was available. The results on sensitivity are consistent with those associated with payoff variation [Lippmannetal., J. Acoust. Soc. Am.59, 129–134 (1976)], but are inconsistent with those reported for presentation probability variation in tone frequency identification [Cuddyetal., J. Exp. Psychol.100, 218–220 (1973)]. In an auxilliary experiment concerned with tone frequency identification, results consistent with those obtained for intensity, but inconsistent with those reported by Cuddyetal., were obtained.

ISSN:0001-4966    

DOI:10.1121/1.388700

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

A series of masking experiments was performed with the aim of comparing frequency selectivity for the monaural and binaural systems. The masking stimulus used in this study combined a sinusoid, which was gated simultaneously with the signal, with a continuous broadband noise. Signal frequency was fixed at 500 Hz. In one condition, the tonal masker and noise were interaurally in phase and the signal was phase reversed. In a second condition, noise, tonal masker, and signal were presented to one ear alone. Signal thresholds were obtained as a function of masker frequency for these two conditions. After making an appropriate selection of noise levels, masking functions for the monaural and binaural system conditions were found to agree closely except for a region about their tips where the binaural condition was more detectable. Two possible interpretations of these results are discussed. Either the monaural and binaural systems contain filters each which have similarly shaped skirts, or the frequency selectivity observed under both diotic and dichotic conditions (for large frequency separations of masker and signal) reflect the operation of a common peripheral filter.

ISSN:0001-4966    

DOI:10.1121/1.388861

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Acoustical impulse responses of the external ear system are measured in order to investigate human three‐dimensional auditory localization. A sound source of electric spark discharge is presented in nine directions for each of four vertical planes, 1.5 m from the center of the subject’s head. The results show that a human pinna works as a compound sound reflector which produces major reflected components within 350 μs. The relationship between the direction of the sound source and the impulse response is clearly shown by the use of an envelope formation technique and radial ray displays.

ISSN:0001-4966    

DOI:10.1121/1.388809

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

The attenuation characteristics of ten commercially available hearing protectors (five muffs and five plugs) were examined for 1/3‐octave bands of noise centered at 1000, 2000, 3150, 4000, and 6300 Hz in ten normal‐hearing young adults utilizing four psychophysical procedures. One of these procedures, the real‐ear attenuation at threshold procedure described in the American standard for the evaluation of hearing protectors, is designed for use at 1/3‐octave band noise levels below approximately 50 dB SPL. Three real‐ear psychophysical procedures were also developed and evaluated. These procedures were: (1) a reaction‐time paradigm; (2) a loudness magnitude‐estimation procedure; and (3) a masked bone‐conduction threshold technique. Each procedure was designed to evaluate protectors for 1/3‐octave bands of noise having levels ranging from approximately 50 to 90 dB SPL. Mean data indicated that: (1) attenuation was linear over the range investigated, although some exceptions to this generalization were apparent; (2) attenuation estimates derived with the reaction‐time and magnitude‐estimation paradigms were typically less than those obtained with the other two methods; and (3) all attenuation estimates, regardless of procedure, were less than manufacturer’s specifications for the majority of the protectors. Implications for existing standards are discussed.

ISSN:0001-4966    

DOI:10.1121/1.388810

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

The free‐field response of TDH 39 earphones, mounted in MX 41/AR cushions, is determined by loudness comparisons in an anechoic chamber. Based on these data, a passive equalizing network with two resonances at 720 and 6000 Hz is developed and realized. When used with this free‐field equalizer, the earphone TDH 39 produces a free‐field equivalent level independent of frequency within ±2.5 dB in the frequency range 100 Hz to 10 kHz. Because of the small differences between TDH 39 and TDH 49 earphones it is expected that the equalizer can also be successfully applied with the TDH 49.

ISSN:0001-4966    

DOI:10.1121/1.388811

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP