Robert H. Brey

Brain stem electrical responses of stutterers and normals by sex, ears, and recovery

Abstract Auditory brainstem electrical responses (BSER) of right and left ears of active stutterers, recovered stutterers, and nonstutterers, both male and female adults, were obtained at click rates of 11.1 and 71.1/sec. Latency intervals of waves I, III, and V were measured. The auditory systems of subjects were stressed using a rapid rate of 71.1 clicks/sec. The latency of wave V was used as the measure of the stress condition. Analysis of variance was used to determine statistical significances of main effects and interactions of mean BSER (waves I, III, V, and wave V in stress condition) of left and right ears of male stutterers (active and recovered), female stutterers (active and recovered), and male and female nonstutterers. With one exception, all main effects and all higher order interactions were nonsignificant. The one main effect that was significant was gender. Females have significantly faster rates of neural transmission than do males. The question was raised, does this finding contribute toward an explanation of the sex ratio in stuttering?

Application of the LMS adaptive filter to improve speech communication in the presence of noise

A major complaint of individuals with normal hearing and hearing impairment is a reduced ability to understand speech in a noisy environment. An adaptive LMS filter was employed to process speech in signal-to-noise ratios (S/N) varying from -8 to +12 dB. The filter configuration is commonly called noise cancellation. Intelligibility measures were obtained on normal and hearing impaired individuals using CID-W22 word lists. For the normal subjects mean intelligibility scores unprocessed were near zero for the S/N ratios -8, -4, and 0 dB and increased from 30 to 50% for the same S/N ratios when processed. For S/N ratios of +4 through +12, mean intelligibility scores prior to filtering ranged from 24 to 46%; after filtering, the scores improved from 67 to 75% i.e., within 7% of the nolse-free sound-field recordings. Preliminary data for the hearing impaired showed the same pattern with their improvement also approaching the scores obtained with no noise present in the sound field.

Monaural perception of the rapidly alternating speech perception test (RASP)

One test that claims to measure binaural fusion, and is routinely utilized as a measure of central auditory function, is the rapidly alternating speech perception (RASP) test. There has been some controversy over the clinical validity of this test. The purpose of this study was to investigate information contained in a single channel of the RASP. Twenty‐four normal hearing subjects listened to one channel of the RASP: twelve to channel 1, twelve to channel 2. Sentence scores for a single channel of the RASP ranged from 0% to 70%, with mean sentence scores for subjects listening to channels 1 and 2 of 37.72% and 20.8%, respectively. An ideal binaural fusion test would contain no, or very little, information when listening to only one channel. It is possible that a single channel of the RASP contains too much information. Many of the sentences were repeated correctly, in their entirety, by at least a few of the subjects listening to either channel in isolation, a task previously assumed to be possible only ...

Aural signal processing in the context of a digital hearing model

A nonlinear model of the human aural system is proposed. Utilizing a homomorphic transformation, the model is implemented in a digital computer and accounts for the Fletcher critical bands in hearing, the nonlinear relationship between input sound intensity and perceived loudness known as recruitment, as well as the thresholds of audibility and the maximum tolerance threshold. The transformed or output signal domain is identified as a perceptual space. It is shown that the model can be used to reproduce the Fletcher Munson equal loudness contours for normal hearing populations. Modification of easily measured parameters results in the generation of equal loudness contours for hearing impaired individuals. Through a combination of the forward homomorphic transformation for normal hearing to the perceptual domain and the inverse mapping utilizing parameters of a hearing impaired individual, it is shown that hearing intelligibility is dramatically improved. It is postulated that signal processing performed i...

The effects of microphone placement and azimuth on peak sound pressure level of type A impulses

Single, repeatable type A impulses were generated by colliding steel spheres in an acoustically reverberant room, and measured as A‐weighted sound levels by a sound level meter having four exponential time averaging modes with time constants ranging from 2 μs to 1 s. Measurements using peak hold (2‐μs time constant) were then obtained on KEMAR at four azimuths and four microphone placements at each azimuth. Comparative measurements showed peak hold to give the most accurate estimation of A‐weighted sound level, as verified electrically. The remaining three underestimated this value. Maximum underestimation of 34.8 dB was demonstrated using the slow time constant. KEMAR measurements demonstrated peak A‐weighted sound levels to be sensitive to both microphone placement and azimuth. Measurements made in the reference field and at external microphone placements tended to underestimate peak A‐weighted sound level at the tympanic membrane (TM). Two conclusions were reached. Time constant of the exponential time...

Real-ear Masking Calibration for Portable Pure-Tone Audiometers

A transformer mixing network is described which allows the calibration of broad-band masking for portable audiometers that lack a built-in mixing network. For many instruments the transformer netwo...

Effect of alcohol on acoustic reflex relaxation

The Reflex Relaxation Index (RRI) was introduced by Norris et al. [Arch. Otolaryngol. 99, 194–97 (1974)] as an objective test for sensorineural hearing loss. The test consists of measuring the acoustic reflex response to pulsed pure tone stimuli. Sensorineural loss subjects show a different response pattern due in part to an increased reflex relaxation latency. Brey and Robinette [J. Acoust. Soc. Am. Suppl. 1 63, S53 (1978)] noted that post stimullus reflex latencies were increased for normal hearing subjects following the ingestion of alcohol. In the present study eleven normal hearing subjects were given the RRI test under two alcohol conditions: blood alcohol levels of 0.00 and 0.10%. Results showed six of the eleven subjects changed from a diagnosis criteria of normal cochlear function to that of sensorineural loss following alcohol consumption. Data suggests a simple positive or negative interpretation of the RRI test is not always appropriate.

Effects of alcohol on the latency of the acoustic reflex

A comparative study was conducted on the relative latency of the acoustic reflex in alcoholic vs. nonalcoholic test sessions on seven normal hearing adults. Acoustic reflex data were collected using impedance audiometry. Reflex eliciting stimuli were a 500‐Hz pure tone, and a low frequency band of Noise 500–1000‐Hz wide. The parameters analyzed were defined as: (1) L1, the onset of the signal to the initiation of the reflex, (2) L2 the initiation of the reflex to 90% of the maximum amplitude, (3) L3, the offset of the signal to the initiation of the reflex decay, and (4) L4, the initiation of the reflex decay to 10% of the maximum amplitude. Alcohol levels were monitored using a breath‐analyzer test. Results showed that overall, alcohol had little effect on the L1 and L3 durations, whereas, the L2 and L4 latencies were longer in the alcohol than in the nonalcohol condition. There was a definite trend toward increased variability among the subjects for all responses under the alcohol condition when compared to the nonalcohol condition. [Work supported by NIH.]A comparative study was conducted on the relative latency of the acoustic reflex in alcoholic vs. nonalcoholic test sessions on seven normal hearing adults. Acoustic reflex data were collected using impedance audiometry. Reflex eliciting stimuli were a 500‐Hz pure tone, and a low frequency band of Noise 500–1000‐Hz wide. The parameters analyzed were defined as: (1) L1, the onset of the signal to the initiation of the reflex, (2) L2 the initiation of the reflex to 90% of the maximum amplitude, (3) L3, the offset of the signal to the initiation of the reflex decay, and (4) L4, the initiation of the reflex decay to 10% of the maximum amplitude. Alcohol levels were monitored using a breath‐analyzer test. Results showed that overall, alcohol had little effect on the L1 and L3 durations, whereas, the L2 and L4 latencies were longer in the alcohol than in the nonalcohol condition. There was a definite trend toward increased variability among the subjects for all responses under the alcohol condition when compare...