Alan S. Feldman

On the Effect of Practice and Motivation on the Threshold of Audibility

The thresholds of audibility for 100 and for 1000 cps have been measured on five groups of originally naive listeners by various experimental techniques. All the experiments showed improvement of the threshold with practice. The improvement was greater at 100 cps than at 1000 cps. Pretraining at 1000 cps did not affect the threshold change at 100 cps. The improvement of the threshold with practice was enhanced considerably by reward and feedback.

Post‐Mortem Acoustic Impedance of Human Ears

By means of a portable acoustic bridge, it is now possible to measure the acoustic impedance at the eardrum of fresh human cadavers. Comparison with the acoustic impedance determined by the same method and with the same instrumentation on live subjects shows that the impedance increases considerably after death. Consequently, results obtained on cadaver ears cannot be applied directly to the middle‐ear function during life.

The role of the middle ear in acoustic trauma from impulses

Exposure to high intensity impulse noise may produce a wide range of audiometric and histological effects in experimental animals. The objective of this study was to assess the changes in the middle ear mechanism after impulse noise exposure and to relate these changes to the audiometric and histological effects.

Acoustic reflex threshold of the chinchilla as a function of stimulus duration and frequency

Acoustic reflex thresholds and the threshold‐duration function were obtained from 27 chinchilla. The reflex threshold was found to be approximately 20 dB lower than that of man with a small frequency effect evident after correction for sound pressure transformation function of the pinna and external auditory meatus. The temporal integration function reflected by acoustic reflex threshold is of much greater magnitude than that obtained psychophysically in chinchilla and man.Subject Classification: [43]65.50, [43]65.24, [43]65.68.

The Role of the Middle Ear in Acoustic Trauma from Impulses

The purpose of this experiment was to evaluate the role of the middle ear in acoustic trauma following high‐level impulse noise exposure. Eleven monaural chinchillas were exposed to either 161‐ or 166‐dB peak SPL impulses of 1‐msec “A” duration, presented at the rate of 1 per minute for 50 minutes. Auditory thresholds were measured before and at regular intervals after exposure, using the evoked response technique; middle‐ear status was evaluated by means of impedance tympanometry. At 30 days the animals underwent tympanotomy for middle‐ear examination followed by sacrifice for surface preparation histology. The 161‐dB group showed the widest range of TTS with two animals exhibiting PTS. Tympanometric examination was suggestive of tympanic membrane stress (i.e., double‐peaked tympanograms). The 166‐dB group showed moderate TTS but no PTS; however, all animals had tympanic membrane perforations which required 10 to 30 days to heal. No gross changes were observed in the ossicular chains at tympanotomy. The ...

Some Effects of Experience on the Threshold of Audibility

The question whether the measured threshold of audibility improves with experience has widespread implications. It refers to the nature of the threshold itself, but it also affects the psychophysical experiments involving comparisons of thresholds of audibility. If practice has no effect, then the amount of experience of the listeners can be disregarded and results obtained on groups of listeners with unequal sophistication may be compared with each other. If the opposite is true, experiments using threshold comparisons would require either pretaining of the listeners or careful counterbalancing. In several experiments, inexperienced listeners showed statistically significant improvement in their threshold of audibility with practice. Depending on the experimental conditions, the average improvement amounted to from 4 to 10 db. Experiments performed on several groups of listeners under similar conditions, yielded practically identical results.