Efficacy of 3 commonly used hearing aid circuits: A crossover trial. NIDCD/VA Hearing Aid Clinical Trial Group.

CONTEXT: Numerous studies have demonstrated that hearing aids provide significant benefit for a wide range of sensorineural hearing loss, but no carefully controlled, multicenter clinical trials comparing hearing aid efficacy have been conducted. OBJECTIVE: To compare the benefits provided to patients with sensorineural hearing loss by 3 commonly used hearing aid circuits. DESIGN: Double-blind, 3-period, 3-treatment crossover trial conducted from May 1996 to February 1998. SETTING: Eight audiology laboratories at Department of Veterans Affairs medical centers across the United States. PATIENTS: A sample of 360 patients with bilateral sensorineural hearing loss (mean age, 67.2 years; 57% male; 78.6% white). INTERVENTION: Patients were randomly assigned to 1 of 6 sequences of linear peak clipper (PC), compression limiter (CL), and wide dynamic range compressor (WDRC) hearing aid circuits. All patients wore each of the 3 hearing aids, which were installed in identical casements, for 3 months. MAIN OUTCOME MEASURES: Results of tests of speech recognition, sound quality, and subjective hearing aid benefit, administered at baseline and after each 3-month intervention with and without a hearing aid. At the end of the experiment, patients ranked the 3 hearing aid circuits. RESULTS: Each circuit markedly improved speech recognition, with greater improvement observed for soft and conversationally loud speech (all 52-dB and 62-dB conditions, P

Reliability of evoked responses to high-frequency (8-14 kHz) tone bursts.

Instrumentation to evaluate the auditory brainstem response to high-frequency (8-14 kHz) tone bursts has been developed in the Auditory Research Laboratory, Portland, Oregon VA Medical Center. This system is intended to monitor the audition of patients receiving ototoxic drugs who are unresponsive to behavioral test procedures. The reliability of responses obtained with the high-frequency tone-burst system was studied in 30 normal ears. Intrasubject variability of intersession data from response waves I, III, and V to tone bursts of frequencies 8, 10, 12, and 14 kHz was not significantly different from click response variability. The results of this study demonstrate the reliability of the ABR to these high-frequency tone-burst stimuli. This technique may provide early identification of hearing loss in unresponsive subjects receiving treatment with potentially ototoxic agents, thus allowing alternative treatments to minimize or prevent communicative handicap.

Age categorization of high-frequency auditory threshold data.

This article presents high-frequency (8- to 20-kHz) auditory threshold measurements for 157 subjects with normal conventional hearing, ranging in age from 6-30 years. Normative descriptive data are provided in five semidecade age categories. Intra-age category mean and variance values for threshold sensitivity and interaural threshold differences are included. Generally, the data are consistent with the expectation of a gradual diminution of high-frequency sensitivity through the adolescent and early adult years. Several unresolved issues related to high-frequency normative data and clinical applicability of high-frequency threshold measurements are discussed.

A prospective study of high-frequency auditory function in patients receiving oral neomycin.

Orally administered, neomycin is reported to cause ototoxicity rarely. Most reports on hearing loss due to oral neomycin have been case studies. One prospective study of a pediatric sample demonstrated a significant loss of hearing in the frequency range of 2 to 8 kHz in 9 of 17 children. To our knowledge there are no published prospective studies on this type with adult samples and therefore little is known of the true incidence or nature of ototoxicity from oral neomycin. This prospective study presents the results of long-term use of oral neomycin in 30 adult subjects. Hearing sensitivity was serially monitored in the frequency range 250-20,000 Hz. Two of the 30 subjects subsequently revealed ototoxicity. Thus the results of this investigation suggest that clinical use of oral neomycin implies relatively little risk of ototoxicity.

Self-monitoring behavior in a case of severe auditory agnosia with aphasia.

This case report describes an unusual combination of speech and language deficits secondary to bilateral infarctions in a 62-year-old woman. The patient was administered an extensive series of speech, language, and audiologic tests and was found to exhibit a fluent aphasia in which reading and writing were extremely well preserved in comparison to auditory comprehension and oral expression, and a severe auditory agnosia. In spite of her auditory processing deficits, the patient exhibited unexpected self-monitoring ability and the capacity to form acoustic images on visual tasks. The manner in which she corrected and attempted to correct her phonemic errors, while ignoring semantic errors, suggests that different mechanisms may underlie the monitoring of these errors.

Detection of aminoglycoside ototoxicity by high-frequency auditory evaluation: selected case studies.

A practical monitoring procedure utilizing frequencies higher than those tested by conventional audiometry for the detection of ototoxicity has the potential for preventing or minimizing irreversible communication deficits in patients receiving aminoglycoside antibiotic therapy. If ototoxicity produced by these drugs could be detected before it progresses to involve the frequencies essential for communication, it might be possible to lower the dose or to change to another antibiotic to prevent a permanently handicapping hearing impairment. From a total of 77 patients monitored by serial audiograms, three case studies illustrate the various types of auditory sensitivity changes observed with high-frequency audiometry. Ototoxicity was generally detected by high-frequency auditory testing before it could be detected by conventional audiometric procedures. These cases demonstrate the utility of monitoring audition at frequencies higher than those tested conventionally in patients receiving aminoglycoside antibiotics.

Early detection of cisplatin ototoxicity. Selected case reports.

A recently developed high frequency auditory measurement technique was applied to a sample of patients receiving the antineoplastic agent cis-dichlorodiammineplatinum II (cisplatin [CDDP, DDP]). Ototoxicity as a result of cisplatin administration is well documented. The ability to detect ototoxicity, however, varies with the methods and instrumentation utilized, and the criteria by which ototoxicity is defined. The auditory function of subjects receiving cisplatin for genitourinary tumors and head and neck cancers was serially monitored with conventional audiometry and with a high frequency testing system. Results reveal a high incidence of nonreversible cochlear toxicity with a predilection for involvement of the higher frequencies. Cochlear toxicity was detected earlier with the high frequency evaluation system than with conventional audiometry. The case reports presented are characteristic of the type and magnitude of auditory changes observed.

An investigation of the validity of high-frequency audition.

In this investigation, a masking experiment was utilized to explore the validity of high-frequency audition. Threshold shifts produced by a narrow-band noise with sharp filter slopes and variable center frequency were determined for pure-tone stimuli from 8000 to 14 000 Hz. Subjects were young adults with normal hearing from 250 through 8000 Hz, and with high-frequency thresholds comparable to those obtained in a previously conducted normative survey. After pure-tone thresholds were obtained for each test frequency, a narrow-band masker was presented ipsilateral to the pure-tone stimulus with center frequency equal to the pure tone. The masker was adjusted to an intensity level necessary to shift the pure-tone threshold approximately 17 dB. The center frequency of the masker was then decreased in discrete steps with the pure-tone threshold re-established at each step. The experimental results, as demonstrated by release-from-masking functions, are consistent with the expectation of increased masker effectiveness as the center frequency of the masker approximates the test frequency. The findings of this investigation suggest that responses to high-frequency auditory stimulation are the result of high-frequency perception, and not the perception of some lower frequency distortion process.

The effects of noise upon human hearing sensitivity from 8000 to 20 000 Hz.

High-frequency (8 to 20 kHz) hearing sensitivity was compared in thirty-six, 20 to 29-year-old military veterans with histories of steady-state or impulsive noise exposure. Threshold shifts were prominent for the steady-state noise subjects from 13 to 20 kHz. Mean thresholds from 8 through 12 kHz were maximally 20 dB poorer than a sample of young adult normals. Audiometric configurations for this group were generally smooth and symmetrical above 8000 Hz. For the impulsive noise group, substantial shifts in sensitivity were seen from 2 to 20 kHz and the high-frequency audiometric configurations were often jagged and/or asymmetrical. The variability of subjects in this group was greater than that seen in the steady-state noise exposed sample. Several case studies are presented to illustrate these characteristics. Measurement of auditory sensitivity from 8 to 20 kHz extends the mapping of basal cochlear function, providing information which often is not predictable from conventional audiometric measurement. This additional information provides for more comprehensive inter- and intra-subject comparison of the degree and extent of threshold changes present.

The effects of impulsive noise upon human hearing sensitivity (8 to 20 kHz).

The effects of impulsive noise exposure upon hearing sensitivity from 8000 to 20000 Hz were determined for a sample of 23 young military veterans. The subjects' histories consisted primarily of major incidents of weapons fire. Based on audiometric configuration, the subject sample was divided in two groups characterized by predominantly unilateral or bilateral shifts in threshold sensitivity. This division was consistent with history information. The main finding was extensive threshold shifts from 8000 to 20000 Hz which was highly individual-specific and unpredictable. High frequency audiometry frequently revealed extensive changes not evident in the 250 through 8000 Hz range.

Effects of steady-state noise upon human hearing sensitivity from 8000 to 20 000 Hz.

Young adults with steady-state noise exposure histories were evaluated with a high frequency (8--20 kHz) test system. High frequency hearing threshold shifts were most prominent from 12-20 kHz and were often highly individual-specific. Good standard range (.25-8 kHz) sensitivity does not assure good hearing above this region. Mild through severe threshold changes may be present. High frequency testing expands monitoring audiometry and has potential special application to hearing conservation programs.

A system for evaluating auditory function from 8000--20 000 Hz.

A system for the measurement of auditory function from 8000--20 000 Hz is described. This system introduces advances in: (a) maximum power output, (b) signal fidelity, and (c) transducer characteristics. Two case studies are presented to illustrate the clinical information gained from the measurement of high-frequency auditory sensitivity, which is not readily apparent in conventional threshold assessment.

2AFC versus standard clinical measurement of high frequency auditory sensitivity (8--20 KC/S).

A two-alternative forced choice (2AFC) psychophysical method of assessment was employed to judge the validity of using a standard clinical test procedure for obtaining thresholds in the frequency region 8--20 kc/s. Close agreement was demonstrated between "same-day" thresholds obtained with a standard clinical test procedure and the 2AFC method, for 6 well trained normal-hearing adults. In addition, close agreement was shown between the 2AFC sensitivity measure and the mean of thresholds obtained at 4 separate times during this investigation with the standard method. The standard clinical test method demonstrated good between-test reliability. It is concluded that a standard clinical test technique is a valid and feasible clinical measurement procedure for this high frequency region.

Acoustic reflex threshold measurement in hearing aid selection.

Aided speech discrimination scores were obtained for 18 patients with sensorineural hearing loss. Monosyllabic word discrimination lists with a competing message of connected discourse at a signal-to-noise ratio of +10 dB were used as the test stimuli, and measurements were made at four hearing aid gain settings for each subject. One of the gain settings was determined by measuring the acoustic reflex threshold for filtered noise in the ear contralateral to the aided ear. Two other settings were at +/- 10 dB relative to the reflex threshold gain setting; the fourth setting was determined with a traditional approach. Mean speech discrimination scores were highest at the reflex threshold gain setting and similar at the other three settings.