Attention effects on distortion-product otoacoustic emissions with contralateral speech stimuli.

This study investigated the effect of selective attention on the distortion-product otoacoustic emission (DPOAE) level through the use of environmentally meaningful, contralateral auditory stimuli. Four different conditions were used for measurement: quiet, contralateral noise, contralateral speech (unattended), and contralateral speech (attended). A statistically significant suppression effect for both the noise and speech conditions was found. However, there was no support for an auditory selective attention effect on the distortion-product amplitude.

The effects of mellow and frenetic music on reported cognitions resulting from auditory subliminal messages.

Building on the work of Henley and Dixon (1974) and Mykel and Daves (1979), we investigated the effects of mellow and frenetic music on reported cognitions resulting from auditory subliminal stimuli. College students (N = 120) were randomly assembled into six groups. One third of the students heard four subliminally transmitted water-related words, one third heard four subliminally transmitted family-related words, and one third heard no subliminal stimuli. Either mellow or frenetic masking music was played for half the students in each group. Students reported more word-related imagery in the mellow music conditions than in the frenetic conditions, although the reported imagery did not correspond with the subliminal messages presented.

Auditory P3 latency and amplitude: relationships to earlier exogenous auditory events.

The purpose of the present study was to determine the relationship for latency and amplitude between exogenous auditory potentials arising at the level of cranial nerve VIII and continuing through the level of the cortex and the auditory P3 endogenous potential. Thirty-four normal hearing adults participated in the study. Binaural ABR, MLR, LCR, and P3 recordings were obtained using 2 kHz tone bursts as the stimulus. Relationships between peak latencies and amplitudes from the early, middle, and late potentials were analyzed using Pearson Product-Moment correlation procedures and multiple regression analyses. Results indicated no significant positive relationships for latency or amplitude between early, middle, or late exogenous potentials and the endogenous P3 potential. Pa of the MLR and P3 demonstrated significant latency/amplitude trading functions. The present data support the hypothesis that P3 latency and amplitude are not related to the latencies and amplitudes of the exogenous responses.

Auditory thresholds in the American cockroach (Orthoptera: Blattidae): estimates using single-unit and compound-action potential recordings.

Recent commercial suggestions that insect populations can be controlled through the use of ultrasound raises the question of whether or not certain insects have receptors that are sensitive to high-frequency sound. Single neural unit discharges and compound-action potentials were recorded from the ventral nerve cord in the American cockroach, Periplaneta americana L., to constant rise time tone pulses from 100 to 40,000 hertz (Hz). Unit responses and compound-action potentials show that the cockroach is insensitive to sound above approximately 3,000 Hz. Data relating latency of the response to intensity of the stimulus suggest that the cockroach cercal system operates on the principle of energy envelope detection. Decreases in latency likely occur primarily as a result of increases in the rate of membrane depolarization in cercal dendrites.

Frequency dependence of interear asymmetries and binaural interaction in the human ABR.

In the present study derived auditory brain stem responses utilizing high pass masking were used to determine the frequency dependence of interear asymmetries and binaural interaction. Eight female adults with normal hearing participated in this study. The ABR was recorded for right and left ears and binaurally with clicks alone and in the presence of high pass masking noise with the following cutoff frequencies: 4000, 2000, 1000, and 500 Hz. Derived responses were obtained by successive waveform subtractions and were analyzed for significant right/left asymmetries, for latency and amplitude, utilizing a statistical method discussed by Spivak (unpublished doctoral dissertation, City University of New York, 1985). The binomial test revealed that the frequency of latency and amplitude asymmetries was not significantly above chance levels for the unmasked measures or for any of the derived bandwidth measures. The binaural interaction component (BIC) was obtained utilizing the method proposed by Dobie and Berlin (Arch Otolaryngol 1979; 105:391-398), and was expressed as a percentage of the true binaural. Analysis of variance revealed no significant differences in the ratio of the BIC amplitude to the true binaural amplitude as a function of the high pass masking cutoff frequency. The present data suggests that for the frequency bandwidths analyzed in this study, there are no specific frequency dependencies of interear asymmetries or binaural interaction in the human ABR.

Monaural and binaural auditory brainstem responses in relation to the psychophysical loudness growth function.

Electrophysiological measures of the brainstem response to auditory stimuli permit comparisons to be made between latency shifts across intensity increments and psychophysical measures of loudness growth. Monaural comparisons leave much room for uncertainty in the interpretation of the nature of the relationship between the two response modes. A more definitive method for examining this relationship is to compare the monaural and binaural data obtained from psychophysical and electrophysiological measures. It is shown here that, while the brainstem electrophysiological response to intensity changes can be described by a power function, the latency of the neural response does not provide a direct link to the process of loudness summation or to the psychophysical response to loudness growth.

Hearing aid volume control taper: Kasten and Lotterman revisited.

In 3 mild, 3 moderate, and 3 high gain aids the gain provided (ave. of .5, 1, and 2 kc/s) was determined as a function of volume control rotation. In the time since the study by Kasten and Lotterman (J. Aud. Res., 1969, 19, 35-39) there appears to have been an improvement in the linearity of the VC taper characteristics for the high gain aids (greater than or equal to 50 db). The mild and moderate gain aids still do not show a linear increase in gain.

Short-term auditory deprivation: effect on brainstem electrical response.

Recent research has associated long-standing conductive hearing losses and changes in brainstem neural responses. Investigations on human subjects to date have used behavioral modes in evaluating response changes for both short-term (induced) and long-term conductive losses. The present study measured brainstem electrical responses (BSERs) from 30 normally hearing adults divided into unilateral-induced conductive-loss groups of 10, 20 and 30 h. This auditory deprivation produced a significant decrease in the wave-I latency (auditory nerve response) across all groups. It is concluded that short-term auditory deprivation can result in VIII nerve fiber hyper-excitability when initially stimulated after the deprivation period. The occurrence of temporary changes under very short-term deprivation raises the possibility that alterations to brainstem neural responses may also be measurable electrophysiologically in individuals with long-term conductive losses, such as children with otitis media.

Maturation effects on the synthetic sentence identification-ipsilateral competing message.

The Synthetic Sentence Identification test with ipsilateral competing message was presented to six groups of six normal-hearing subjects ranging in age from 8 through 25 years to assess whether performance improved as age increased. The scores improved for all age groups as the message-to-competition ratio decreased. Scores also improved as age increased. The interaction effect between age and message-to-competition ratio was significant (P less than 0.001). The results support previous findings and give strong evidence to support there being a maturation factor involved in auditory processing. Establishing normative data for normal-hearing children at various ages as well as data for children having central problems would now be required to make the Synthetic Sentence Identification test with ipsilateral competing message a useful test with children.

Auditory tract asymmetry in brainstem electrical responses during binaural stimulation.

A recently developed technique to demonstrate binaural interaction in brainstem auditory electrical responses was systematically investigated. From analysis of the BSERs of eight normal hearing adults, it was found that variations in binaural interaction difference traces are related to an artificial relationship created by this technique between the true binaural and summed monaural waveforms. The present investigation employed a refinement of the binaural interaction technique whereby left and right monaural waveforms were subtracted individually from the binaural waveform to produce a difference trace. Analysis revealed that variations in the difference trace morphology are related to dependence of binaural latencies on left or right auditory tract preference in the brainstem auditory pathways. Within the subject population, 50% demonstrated an auditory tract preference for binaural latencies while 50% showed no preference. It was concluded that the difference trace is mathematically predictable from the morphological differences between the binaural and monaural waveforms and that a more accurate representation of binaural interaction can be obtained from a comparison of individual monaural waveforms within the binaural trace.

Effect of firetruck noise on firefighters' hearing.

Noise exposure of Minneapolis city firefighters was measured in 3 categories of fire apparatus. Maximum SPL of 110 db(A) and mean duration of 23 min/day do not exceed OSHA guidelines. The means pure-tone ac HTLs of a Group A of 17 men of 23-28 yrs with 0.75-2 yrs firefighting experience did not differ significantly from those of a comparable group of older men of 30-35 yrs with 8.25-10.9 yrs firefighting experience. Mean HTLs for both groups exceeded those of men of comparable age groups with no noise exposure tested by Corso, but at the lower frequencies only (0.5-4 kc/s), not at the higher (6-8 kc/s). Previous military and concurrent recreational noise exposure may have masked differences between Group A and B.

The effects of informative and non-informative speech on the judgment of most comfortable listening level.

Fifteen normal-hearing males and fifteen normal-hearing females were presented with a portion of speech played in a forward and a backward direction. The speech was presented in an ascending manner, and the subjects were asked to make comfortable listening judgments. Results indicated that most comfortable listening level is independent of the direction of the speech stimulus and thus independent of information content. Results also showed that sex of the listener plays an unimportant role in most comfortable listening level. Overall, the results indicated that most comfortable listening level results from clinical populations will be little influenced by the listener's ability to understand the stimulus message and thus little influenced by the degree of reduction to speech discrimination ability.