Journal of the American Auditory Society最新文献

Five normal hearing adults were examined for power spectral analysis of AER to 1000-Hz pure tone. Major frequency components of responses to stimuli at 50 dB hearing level exist at 1 to 14 c/s. The power spectra of responses to stimuli at 10 dB hearing level are greater than those of the SBA in the frequency components between 3 and 9 c/s; furthermore, the total power of 3 to 9 c/s indicates a clear difference between the 2. Incidentally, at 512-msec analysis time, the total power of 3 to 9 c/s of the AER are significantly greater than that at 1024-msec analysis time, whereas those of the SBA show little discrepancy at the 2; thus at 512-msec analysis time, the total power of 4 to 9 c/s yields a clear difference between the AER and the SBA responses averaged over 50 stimuli even at 10 dB hearing level.

An acoustic reflex method of establishing hearing aid gain settings for most comfortable loudness was tested. Forty hearing-aid users were examined to determine relationships among MCL, loudness discomfort level, and the contralateral acoustic reflex to speech, under unaided and aided conditions. Results indicate that a simple 2-part rule results in amplification to most comfortable loudness for 76% of subjects. Implications for establishing hearing aid saturation sound pressure level settings are discussed.

The relationships among most comfortable listening level (MCL), loudness discomfort level, and the acoustic reflex (AR) to speech were studied on cochlear-impaired listeners using earphones and sound field conditions. Recorded sentence materials were presented monaurally in quiet and in the sound field in the presence of 55 dB SPL cafeteria noise. Both unaided and aided sound field testing were done. The results indicated that the MCL and AR fell at approximately the same intensities under all test conditions, whereas the LDL occurred at approximately 18 dB higher intensity. The MCL was elevated by the presence of noise, whereas the AR remained invariant. Also, the AR occurred below the level predicted by the loudness function. The results tend to indicate that although the AR is highly correlated with MCL in cochlear-impaired listeners a cause and effect relationship may not exist.

Acoustic reflexes and uncomfortable loudness levels were recorded for eight normal-hearing listeners on eight separate occasions and eight listeners with sensorineural hearing impairments on three to four occasions. Frequencies tested were 500, 1000, 2000, and 4000 Hz for both measures. Neither acoustic reflexes nor uncomfortable loudness levels was found to vary significantly across sessions for either the normal or hearing impaired listeners. However, significant intensity differences were noted between acoustic reflexes and uncomfortable loudness levels, for both subject groups, and these differences were dependent upon subject and frequency.

Among the available auditory rehabilitative resources, automatic gain control (AGC) hearing aids comprise a unique class of personal amplifying systems. They are unique because of their capability of achieving some degree of self-regulation. However, partly due to the standard methods of portraying and describing electroacoustic data for conventional (non-AGC) aids, certain characteristics of AGC aids, such as are related to signal and noise relations over time, seem to be commonly unappreciated by the typical clinician. This paper discusses some principles of amplifying behavior that are common to all AGC hearing aid systems, as well as various design modifications. The ramifications of these properties are pointed out with a view towards greater clinical implementation of the available technology.

The Word Intelligibility by Picture Identification test was recorded with electret microphones inserted at the ear canals of a child listener. This recording paradigm has been shown to preserve binaural cues. Thirty normal-hearing children (ages 6 to 14) responded to binaural and monaural stimulation under auditory and auditory/visual presentation at six signal-to-noise (S/N) ratios (varying from +3 to -12 dB). At the higher and lower S/N ratios, the binaural advantage was minimized. For the auditory alone mode, the largest mean difference of 21% intelligibility improvement from monaural to binaural presentations occurred at -6 dB S/N, whereas in the auditory/visual mode, an intelligibility improvement of 20.8% occurred at -9 dB S/N. Implications for binaural amplification for the hearing impaired who operate on minimal residual hearing follow from the results of this study.

Marked asymmetry of auditory function between left and right ears would normally be indicative of some abnormality. This study was designed to investigate the limits of tympanometric symmetry in normal individuals. A limiting ratio of 4/3 between left and right ear compliances is suggested. Applying this criterion and strict criteria for normality of middle ear pressure and reflex thresholds, a value for middle ear compliance was obtained with a considerably smaller range for "normality" than from previous studies. A marked difference between middle ear compliances of male and female subjects was observed, and evidence was adduced to suggest that this was due to differences in size of the ear canal and tympanic membrane.

The repeatability of W-22 PB tests at levels of speech reception threshold (SRT) plus 5 to 30 dB in quiet and in white noise at S/N = 0 and 7 dB at a level of SRT plus 20 dB for 28 subjects with sensorineural hypoacusis. Standard deviations at various levels were from 9 to 13% compared to a standard deviation of less than 8% at SRT plus 40 dB. The lower variability at SRT plus 40 dB permits satisfactory confidence in the average of two measurements. However, it was found that more tests are required for the same confidence at the lower sensation levels. A protocol is suggested for carrying out this requirement.

Traditional peripheral hearing tests (pure-tone thresholds, speech reception thresholds, and speech discrimination) and selected "central" hearing tests were administered to three commissurotomized patients. One patient was tested both pre-and postoperatively, whereas the remaining two were tested only postsurgery. Results indicated that commissurotomy had no apparent effects on performance on the peripheral tests. However, various tests in the central battery showed definite abnormal results. Most significant were the results from dichotically presented speech stimuli which repeatedly showed total absence of responses for stimuli presented to the left ear. Additional experimentation indicated this monaural deficit could be overcome by reducing the intensity level of right ear stimuli. Results for low-redundancy, monotically presented speech stimuli also indicated a left ear deficit; however, these results were not as consistent as the dichotic data.