Performance of dual-microphone in-the-ear hearing aids.

Fifty subjects with mild to moderate-severe sensorineural hearing loss and prior experience with binaural amplification were evaluated at two sites (25 subjects at each site). Signal-to-noise ratios (SNRs) were measured using the Hearing in Noise Test (HINT) after each subject wore binaural in-the-ear hearing aids programmed for omnidirectional and dual-microphone performance, for 4 weeks. Both microphone conditions were evaluated under "ideal" (signal at 0 degrees; noise at 180 degrees) and "diffuse" (signal at 0 degrees; correlated noise at 45 , 135 degrees, 225 degrees, and 315 degrees) listening conditions. Results revealed statistically significant mean improvements in SNRs between 3.7 and 3.5 dB at Site I and 3.2 and 2.7 dB at Site II for the ideal and diffuse listening conditions, respectively, for the dual-microphones in comparison to the performance provided by the omnidirectional microphone.

Comparison of performance with a conventional and a two-channel hearing aid.

Twenty experienced binaural hearing aid users evaluated a two-channel behind-the-ear instrument, with a low band that offered dynamic range compression and a high band that provided linear amplification. After a 5-week trial period, data from the Profile of Hearing Aid Performance (PHAP), the Speech Perception in Noise (SPIN) test, as well as 2-cm3 coupler measurements were compared for the two-channel experimental device and the subjects' single-channel aids. Most subjects showed significant improvement on the SPIN test and on the PHAP with the two-channel aid. Subjective comments were predominantly enthusiastic, and 17 subjects (85%) chose to exchange their present instruments for the experimental aid. After a total of 19 weeks experience with the two-channel hearing aid, 15 subjects were reevaluated; the mean scores for the SPIN test and for most of the PHAP subscales were unchanged from those observed at the 5-week assessment.

Vestibular abnormalities in patients with Bell's palsy.

In order to assess the extent of the underlying pathology in Bell's palsy, the vestibular function of 24 patients was evaluated within the first week from the onset of facial paralysis. Seven patients had pathological findings by ENG and an additional three had subjective vestibular signs; four of these ten patients also showed abnormal auditory brain stem evoked potentials. There was no correlation between the severity of the paralysis or the prognosis for recovery and the presence of vestibular abnormalities.

The variability of fixation suppression of caloric-induced nystagmus.

Twelve normal adults were evaluated to determine their capacity to suppress caloric-induced nystagmus by visual fixation. Fixation suppression (FS) was assessed four times during the routine Fitzgerald-Hallpike caloric procedure. The results were characterized by large inter-subject as well as intra-subject variability. It is cautioned that diagnostic categories should not be inferred on the basis of absolute numeric values of FS.

Tympanometric assessment of eustachian tube function of divers.

The Eustachian tube swallow test (ETST) proposed by Williams (1975. Ann. Otol. Rhinol. Laryngol. 84, 339-343) and Bluestone (1975. American Electromedics Corp, New York) was performed on both ears of 62 otologically normal young adult participants in a scuba diving course. The results of the ETST were evaluated according to various pass-fail criteria. A 95% pass rate was achieved only when applying the most lenient criteria, those which considered a minimal shift in either tympanometric peak pressure or amplitude. There was no relation between the subjects' performance on the ETST and the otoscopic evidence of barotrauma after an actual dive. The ETST was of no practical value in screening prospective divers.

Auditory brain-stem evoked potentials in Bell's palsy.

In an attempt to assess objectively the integrity of the auditory pathways in patients suffering from Bell's palsy, an audiometric evaluation was performed and auditory brain-stem evoked potentials (ABEP) were obtained from 24 patients within the first week from the onset of facial weakness. Despite negative audiometric findings, significant ABEP abnormalities (greater than 2.5 SDs) were observed for 25% of the sample. In each case the ABEP deviation suggested prolonged brain-stem conduction time; for some patients the aberration was only apparent with an increased stimulus repetition rate. The ABEP measures were found to be independent of the side or severity of the paralysis, the acoustic reflex, or reported dysacusis. The ABEP was of no value in predicting recovery of facial muscle function. It is suggested that the facial paralysis may be only the overt manifestation of a generalized pathologic condition.

Factors influencing use of hearing aids.

A follow-up questionnaire was mailed to new hearing aid users. The questionnaire responses of 430 persons, 73% of the sample, were related to age, audiometric, and hearing aid evaluation data obtained at the time of fitting. Reported usage of the aids was also analyzed in terms of the type of fitting and according to length of postfitting training. Further, the reasons for limited or nonuse were tabulated. The population in the present study, in comparison with that of previous investigations, was characterized by relatively young age and predominantly noise-induced, sensorineural type hearing loss, with mild hearing loss for speech; these factors led to a high proportion of selective amplification fittings. Reported overall use did not differ among the types of aids. Overall use declined with increasing age, and the majority of persons in this population used their aids selectively rather than on a full-time basis. Length of postfitting training appeared to increase hearing aid use. Mean audiometric and hearing aid evaluation data remained relatively constant across four usage categories: "always," "often," "occasionally," and "never." Excessive background noise and lack of need constituted 63% of the reasons given for limited use or nonuse.

The reliability and validity of the comfort level method of setting hearing aid gain.

The comfort level method (Carhart, 1946) probably is the most widely used procedure for setting the acoustic gain of hearing aids. A series of experiments were conducted to determine the test-retest reliability of the comfort level method and the relationship between the comfort settings established in a clinical test suite and the comfort settings utilized in more realistic daily listening situations. Adults with bilateral sensorineural hearing impairments were subjects. The results suggest that the comfort level method has good test-retest reliability for most clinical purposes. Further, clinically established comfort settings may accurately represent typical daily-use settings if the input level used to establish the comfort settings in the clinical environment is 70 dB SPL.

Masking level difference for speech: effects of ear dominance and age.

A comparison was made of right and left ear discrimination of monosyllables presented with competing 'cocktail party' in conditions of signal monaural-noise monaural, and signal monaural-noise binaural and in-phase interaurally. The effects of these conditions were compared in 20 normal children aged 5-6 years, 40 normal young adults and 20 adults aged 66-76 years. The magnitudes of right and left ear masking level differences (MLDs) were compared at each age level. (1) MLDs occurred for all three age groups; (2) for the two adult age groups, mean right ear scores exceeded mean left ear scores in the case of monaural noise presentation, although the difference was significant only for the young adults; (3) no interaural difference appeared for the children, and (4) marked variability of the magnitude of the MLDs occurred among subjects of all three age groups.

Measurement of the acoustic reflex without a pressure seal.

Obtaining a hermetic seal in the external auditory canal is often a major obstacle in impedance audiometry. In the present study, the acoustic reflex threshold was determined for three groups of subjects, first with and then without a pressure-tight seal. It was found that for subjects with normal hearing or sensorineural hearing loss and normal tympanograms, 96% of the measurements obtained without a pressure seal were within 5 dB of those obtained with a seal. Among the subjects who exhibited negative middle ear pressure, the acoustic reflex could be measured consistently at the point of maximum compliance, while no response was observed without a pressure seal.