Degradation in Binaural and Spatial Hearing and Auditory Temporal Processing Abilities as a Function of Aging.

Objective: Sensorineural hearing loss is common with advancing age, but even with normal or near normal hearing in older persons, performance deficits are often seen for suprathreshold listening tasks such as understanding speech in background noise or localizing sound direction. This suggests there is also a more central source of the problem. Objectives of this study were to examine as a function of age (young adult to septuagenarian) performance on: 1) a spatial acuity task examining lateralization ability, and a spatial speech-in-noise (SSIN) recognition task, both measured in a hemi-anechoic sound field using a circular horizontal-plane loudspeaker array, and 2) a suprathreshold auditory temporal processing task and a spectro-temporal processing task, both measured under headphones.

Interaural frequency mismatch jointly modulates neural brainstem binaural interaction and behavioral interaural time difference sensitivity in humans.

The binaural interaction component (BIC) of the auditory brainstem response (ABR) is the difference obtained after subtracting the sum of right and left ear ABRs from binaurally evoked ABRs. The BIC has attracted interest as a biomarker of binaural processing abilities. Best binaural processing is presumed to require spectrally-matched inputs at the two ears, but peripheral pathology and/or impacts of hearing devices can lead to mismatched inputs.

Normative Study of the Binaural Interaction Component of the Human Auditory Brainstem Response as a Function of Interaural Time Differences.

Objectives: The binaural interaction component (BIC) of the auditory brainstem response (ABR) is obtained by subtracting the sum of the monaural right and left ear ABRs from the binaurally evoked ABR. The result is a small but prominent negative peak (herein called "DN1"), indicating a smaller binaural than summed ABR, which occurs around the latency of wave V or its roll-off slope. The BIC has been proposed to have diagnostic value as a biomarker of binaural processing abilities; however, there have been conflicting reports regarding the reliability of BIC measures in human subjects.

Simultaneous bilateral cochlear implantation in adults: a multicenter clinical study.

Objective: To determine the efficacy of "simultaneous" bilateral cochlear implantation (both implants placed during a single surgical procedure) by comparing bilateral and unilateral implant use in a large number of adult subjects tested at multiple sites.

Design: Prospective study of 37 adults with postlinguistic onset of bilateral, severe to profound sensorineural hearing loss. Performance with the bilateral cochlear implants, using the same speech processor type and speech processing strategy, was compared with performance using the left implant alone and the right implant alone.

Hyperacusis: case studies and evaluation of electronic loudness suppression devices as a treatment approach.

Hyperacusis, as defined here, is a relatively rare condition in which the patient, with or without hearing loss, experiences severe loudness discomfort to everyday environmental sound levels. The case studies of 14 patients with severe hyperacusis are described; all wore passive attenuators (earplugs and/or earmuffs) in an attempt to alleviate their discomfort, frequently producing communication difficulties. These subjects were fitted binaurally with experimental electronic loudness suppression devices housed in in-the-ear casings.

Field trial evaluations of a switched directional/omnidirectional in-the-ear hearing instrument.

The use of directional microphones is one of the few methods available for hearing aids to increase the signal-to-noise ratio. The smaller microphones available with today's technology have increased the viability of their application for in-the-ear (ITE) hearing aids. This study evaluated an ITE hearing aid containing two nondirectional microphones that provides wearer-selectable omnidirectional/directional operating modes.

The role of consonant-vowel amplitude ratio in the recognition of voiceless stop consonants by listeners with hearing impairment.

Several authors have evaluated consonant-to-vowel ratio (CVR) enhancement as a means to improve speech recognition in listeners with hearing impairment, with the intention of incorporating this approach into emerging amplification technology. Unfortunately, most previous studies have enhanced CVRs by increasing consonant energy, thus possibly confounding CVR effects with consonant audibility. In this study, we held consonant audibility constant by reducing vowel transition and steady-state energy rather than increasing consonant energy.

Differences in performance between Oticon MultiFocus Compact and ReSound BT2-E hearing aids.

Differences in performance were evaluated between binaural fittings of the Oticon MultiFocus (MF) and ReSound BT2-E on 25 hearing-impaired subjects across two sites. Subjects were initially fit using each manufacturer's algorithm and adjustments were made at 1 week based on subjects' responses to diary questions. Performance was assessed after a 4- to 6-week trial period with each hearing aid set using the Speech Perception in Noise (SPIN) test administered at 50, 65, and 80 dB SPL, the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire, loudness judgments of female connected discourse at 65 and 80 dB SPL, and an overall preference selection.

Effect of low-frequency gain reduction on speech recognition and its relation to upward spread of masking.

Speech recognition was measured in listeners with normal hearing and in listeners with sensorineural hearing loss under conditions that simulated hearing aid processing in a low-pass and speech-shaped background noise. Differing amounts of low-frequency gain reduction were applied during a high-frequency monosyllable test and a sentence level test to simulate the frequency responses of some commercial hearing aids. The results showed an improvement in speech recognition with low-frequency gain reduction in the low-pass noise, but not in the speech-shaped background noise.

Consonant recognition performance of hearing-impaired listeners using one linear and three nonlinear hearing aids.

Consonant recognition performance was examined in 18 subjects listening in quiet and speech noise with linear and nonlinear hearing aids. Subjects were divided into three groups by audiometric configuration: flat, moderately sloping, and sharply sloping. Nonlinear amplification schemes included adaptive high-pass filtering (Argosy's Manhattan II, experimentally modified; MANe), MANe circuitry followed by expansion (EXP), and infinite amplitude clipping (IAC).

Concurrently recorded auditory event-related potentials and behavioral responses to dichotic CV stimuli.

Auditory event-related potentials (AERPs) were recorded concurrently with behavioral responses to dichotic CVs in 16 young, normal, right-handed, female subjects. The results showed the expected behavioral right-ear advantage and an N105-P184 complex of significantly greater amplitude over the left temporal region than over the right. In another normal individual showing a consistent behavioral left-ear advantage, we found differences in AERP amplitude and morphology favoring right-hemispheric lateralization for speech.

Ability to achieve gain/frequency response and SSPL-90 under three prescription formulas with in-the-ear hearing aids.

Custom in-the-ear (ITE) hearing aids (standard linear amplifiers with single-pole-filter low-frequency tone control and a class A amplifier output stage) were fit to 90 ears using the revised National Acoustics Laboratories' formula (NAL-R), and to 20 ears each using Prescription of Gain/Output II (POGO II) and Memphis State University (MSU) formulas. Both real-ear insertion gain and 2-cc coupler gain were evaluated. Examination of differences between prescribed gain and that actually achieved in the fittings revealed that too much gain was often given in the low- and mid-frequency range and insufficient gain in the high frequencies.

Achieving prescribed gain/frequency responses with advances in hearing aid technology.

Technological limitations have restricted the capability of older generation in-the-ear (ITE) hearing aids to closely match prescribed real ear gain/frequency responses. Newer technology, widely available in currently marketed ITE hearing aids, has considerably improved this capability. Data for 60 ears are presented comparing the real ear insertion gain (REIG) actually achieved to the target REIG, using ITE hearing aids having: 1) older generation narrow-band receivers, and amplifiers with single-pole-filter low frequency tone control and a class A amplifier output stage (n = 30), and 2) newer generation amplifiers with a two- or four-pole-filter low frequency tone control, and wide band receivers, containing a class D amplifier output stage (n = 30).

Comparison of Etymotic insert and TDH supra-aural earphones in auditory brainstem response measurement.

There are few systematic comparisons of Etymotic ER-3A insert earphones versus supra-aural earphones in auditory brainstem response (ABR) measurement. We compared ER-3A insert earphones and two types of supra-aural earphones (TDH-39P and TDH-49P) in a group of normal hearing adults. Acoustic analyses revealed spectral and temporal differences among earphones.

A review of current "noise reduction" hearing aids: rationale, assumptions, and efficacy.

Amplification technology has changed considerably in the last decade, particularly with the introduction of more advanced adaptive signal processing approaches and digital/hybrid hearing aids. Because difficulty understanding speech in the presence of background noise is the most common complaint of hearing-impaired patients, an increasing number of these new products are being marketed as "noise reduction" hearing aids. There reamin, however, many unanswered questions regarding patient candidacy for these instruments, and the relative benefit that can be expected from the new technology.

Effects of relative starting phase and frequency separation of two-tone stimuli on the brain-stem auditory-evoked response.

Brain-stem auditory-evoked responses (BAERs) were obtained in six normal-hearing adults using single-tone and two-tone stimuli arithmetically centered around 4000 Hz. Two-tone stimuli varied in frequency separation from 200 to 3200 Hz, and started in-phase (homophasic) or 180 deg out-of-phase (antiphasic) with each other. Responses to each of the single-tone components of the two-tone stimuli were elicited and then summed for comparison with responses to the two-tone stimuli.

Rapid threshold estimation using the "chained-stimuli" technique for auditory brain stem response measurement.

The "chained-stimuli" technique for rapid auditory brain stem response (ABR) threshold estimation involves lengthening the averaging time window and presenting a series ("chain") of click stimuli. Each stimulus chain contains, in addition to a silent interval, click stimuli of 10, 20, 30, 40, 50, 60, and 70 dB nHL that are separated by 10 msec intervals. Using this method, the single averaged response to the chained-stimulus contains up to seven individual ABRs.

Interaural attenuation using etymotic ER-3A insert earphones in auditory brain stem response testing.

Click interaural attenuation (IA) was measured behaviorally and with the auditory brain stem response (ABR) in two unilaterally deaf adults with Etymotic ER-3A insert earphones, and TDH-39P and TDH-49P supraaural earphones. Stimulus crossover for each set of earphones was also determined with pure-tone audiometry. Pure-tone results agreed with previous research, showing that the ER-3A provided substantially greater IA than the supraaural earphones, particularly for low frequencies.

Variability of most comfortable and uncomfortable loudness levels to speech stimuli in the hearing impaired.

Methods for determining hearing aid settings often incorporate measurements of most comfortable loudness (MCL) and uncomfortable loudness (UCL) levels. This study examined the variability of loudness measures and their correlation to threshold data, using speech stimuli presented to hearing-impaired subjects. MCLs, UCLs, speech reception, and speech detection thresholds were obtained from 50 subjects having sensorineural impairments.

The 40-Hz event-related potential as a measure of auditory sensitivity in normals.

Estimates of behavioral threshold using the 40-Hz Event-Related Potential (ERP) were obtained on sixteen normal subjects at frequencies of 500, 1000, 2000, and 4000 Hz, and compared with behavioral thresholds for the same stimuli. The mean differences were within 10 dB at the three lowest frequencies. The mean difference at 4000 Hz was 16 dB.