Home Hearing Test: Within-Subjects Threshold Variability.

BACKGROUND: The Home Hearing Test (HHT) is an automated pure-tone threshold test that obtains an air conduction audiogram at five test frequencies. It was developed to provide increased access to hearing testing and support home telehealth programs. PURPOSE: Test and retest thresholds for 1000-Hz stimuli were analyzed to determine intrasubject variability from two independent data sets. RESEARCH DESIGN: Prospective, repeated measures. STUDY SAMPLE: In the Veterans Affairs (VA) study, results from 26 subjects 44 to 88 years of age (mean = 65) recruited from the Nashville VA audiology clinic were analyzed. Subjects were required to have a Windows PC in the home and were self-reported to be comfortable with using computers. Two subjects had normal hearing, and 24 had hearing losses of various severities and configurations. The National Center for Rehabilitative Auditory Research (NCRAR) sample included 100 subjects (68 males; 32 females) with a complaint of hearing difficulty recruited from the local community and Veteran population. Subjects ranged in age from 32 to 87 years (mean = 63.7 years). They were tested in a quiet room at the NCRAR. DATA COLLECTION AND ANALYSIS: Subjects in the VA study were provided kits for installing HHT on their home computers. HHT was installed on a computer at NCRAR to test subjects in the NCRAR study. HHT obtains a five-frequency air conduction audiogram with a retest of 1000 Hz in both ears. Only the 1000-Hz test-retest results are analyzed in this report. Six statistical measures of test-retest variability are reported. RESULTS: Test and retest thresholds were highly correlated in both studies (r ≥ 0.96). Test-retest differences were within ±5 dB ≥92% of the time in the two studies. Standard deviations of absolute test-retest difference were ≤3.5 dB in the two studies. CONCLUSIONS: Intrasubject variability is comparable to that obtained with manual testing by audiologists in sound-treated test rooms.

Azimuthal auditory localization of gunshots in a realistic field environment: effects of open-ear versus hearing protection-enhancement devices (HPEDs), military vehicle noise, and hearing impairment.

OBJECTIVE: A controlled field experiment was conducted to evaluate localization of suprathreshold gunshot reports (from blank cartridges) with four hearing protection-enhancement devices (HPEDs) in comparison to the open ear with ambient outdoor noise and in 82 dBA diesel military heavy truck noise. DESIGN: Five measures of localization accuracy and response time for eight shooter positions in azimuth were measured. STUDY SAMPLE: Nine normal-hearing and four impaired-hearing participants were tested. RESULTS: Statistical analysis showed worse accuracy and response time performance with the electronic earmuffs (Peltor Com-Tac II™ in full gain position) than with the other tested HPEDs (Etymotic EB 1 and EB 15 High-Fidelity Electronic BlastPLG™ electronic earplugs, both set to Lo gain positions; and 3M Single-Ended Combat Arms™ passive earplug in level-dependent, "open" position). Performance with all HPEDs was worse than that with the open ear, except on right-left confusions, in which the earmuff stood alone as worst, and in response time, for which the EB 1 was equivalent to the open ear. There was no significant main effect of noise on performance. Hearing impairment increased right-left confusions. Subjective ratings related to localization generally corroborated objective localization performance. CONCLUSIONS: None of the tested HPEDs preserved "normal" localization performance.

Are two ears not better than one?

BACKGROUND: The decision to fit one or two hearing aids in individuals with binaural hearing loss has been debated for years. Although some 78% of U.S. hearing aid fittings are binaural (Kochkin , 2010), Walden and Walden (2005) presented data showing that 82% (23 of 28 patients) of their sample obtained significantly better speech recognition in noise scores when wearing one hearing aid as opposed to two. PURPOSE: To conduct two new experiments to fuel the monaural/binaural debate. The first experiment was a replication of Walden and Walden (2005), whereas the second experiment examined the use of binaural cues to improve speech recognition in noise. RESEARCH DESIGN: A repeated measures experimental design. STUDY SAMPLE: Twenty veterans (aged 59-85 yr), with mild to moderately severe binaurally symmetrical hearing loss who wore binaural hearing aids were recruited from the Audiology Department at the Bay Pines VA Healthcare System. DATA COLLECTION AND ANALYSIS: Experiment 1 followed the procedures of the Walden and Walden study, where signal-to-noise ratio (SNR) loss was measured using the Quick Speech-in-Noise (QuickSIN) test on participants who were aided with their current hearing aids. Signal and noise were presented in the sound booth at 0° azimuth under five test conditions: (1) right ear aided, (2) left ear aided, (3) both ears aided, (4) right ear aided, left ear plugged, and (5) unaided. The opposite ear in (1) and (2) was left open. In Experiment 2, binaural Knowles Electronics Manikin for Acoustic Research (KEMAR) manikin recordings made in Lou Malnati's pizza restaurant during a busy period provided a typical real-world noise, while prerecorded target sentences were presented through a small loudspeaker located in front of the KEMAR manikin. Subjects listened to the resulting binaural recordings through insert earphones under the following four conditions: (1) binaural, (2) diotic, (3) monaural left, and (4) monaural right. RESULTS: Results of repeated measures ANOVAs demonstrated that the best speech recognition in noise performance was obtained by most participants with both ears aided in Experiment 1 and in the binaural condition in Experiment 2. CONCLUSIONS: In both experiments, only 20% of our subjects did better in noise with a single ear, roughly similar to the earlier Jerger et al (1993) finding that 8-10% of elderly hearing aid users preferred one hearing aid.

Better protection from blasts without sacrificing situational awareness.

A large number of soldiers returning from war report hearing loss and/or tinnitus. Many deployed soldiers decline to wear their hearing protection devices (HPDs) because they feel that earplugs interfere with their ability to detect and localize the enemy and their friends. The detection problem is easily handled in electronic devices with low-noise microphones. The localization problem is not as easy. In this paper, the factors that reduce situational awareness--hearing loss and restricted bandwidth in HPD devices--are discussed in light of available data, followed by a review of the cues to localization. Two electronic blast plug earplugs with 16-kHz bandwidth are described. Both provide subjectively transparent sound with regard to sound quality and localization, i.e., they sound almost as if nothing is in the ears, while protecting the ears from blasts. Finally, two formal experiments are described which investigated localization performance compared to popular existing military HPDs and the open ear. The tested earplugs performed well regarding maintaining situational awareness. Detection-distance and acceptance studies are underway.

Hearing Protection Success: Musicians Have a Favorable Response to Hearing Protection and Listeners Are Unable to Identify Music Produced by Musicians Wearing Hearing Protection.

BACKGROUND: Musicians are known to be at risk for developing hearing sensitivity and hearing-related problems given their occupational exposure to high-level sound. Among options for hearing conservation, earplugs are an effective and inexpensive choice. Adoption rates for musicians' earplugs remains consistently low, however, given concerns about the impact of hearing protection on their own performance as well as concerns that the resultant music will be a negative experience for listeners. In fact, few studies have (1) examined musicians' attitudes about using hearing protection while performing themselves and (2) determined whether music played by musicians wearing hearing protection sounds different to listeners. PURPOSE: The purposes of this study were (1) to evaluate how wearing musicians' earplugs affected musicians' perception of their performance while they were playing, and (2) to examine whether listeners can distinguish a difference between music recorded by musicians playing with and without earplugs. RESEARCH DESIGN: Experiment 1: student musicians were recorded playing under two conditions (with and without wearing earplugs) and then were surveyed about their experience. Experiment 2: musically experienced and naïve listeners were presented with musical samples played by musicians with and without earplugs in an ABX format. Listeners responded by indicating whether the third stimulus (X) was conditionally identical to the first (A) or second stimulus (B). RESULTS: Experiment 1: while performing, musicians always preferred the no earplugs condition. The majority, however, rated the overall experience of playing with earplugs as generally positive. Experiment 2: listeners were unable to hear a difference between the two recordings. DISCUSSION: In this experiment, musicians rated their experience playing without hearing protection more favorably than their experience playing with hearing protection, but most musicians rated their experience with hearing protection as generally positive. The inability of listeners to distinguish a difference in music played with and without hearing protection suggests that the listening experience may not be adversely impacted by hearing protection worn by the performers. CONCLUSION: Earplugs are an inexpensive, noninvasive strategy for hearing conservation for musicians, and this study indicates that barriers to wearing hearing protection might be less problematic than previously reported.

Comparison of vu-meter-based and rms-based calibration of speech levels.

A difference of approximately 5 dB exists between the level of spoken English determined using the ANSI standard vu-meter method compared to the common root-mean-square (rms) method. If the rms method is substituted for the present ANSI standard method for calibrating a speech audiometer, for example, the reported speech reception thresholds will improve 5 dB: Speech levels read approximately 5 dB less using rms. Similarly, the reported signal-to-noise ratio required to understand speech in a speech-spectrum noise will be 5 dB better using rms. A simple method for obtaining a close approximation to traditional calibrations using a modified rms method is given.

Measurement of individual loudness functions by trisection of loudness ranges.

OBJECTIVES: Loudness-balance measurements with monaurally impaired subjects have shown that the shape of the loudness versus sound-pressure curve among hearing-impaired persons varies significantly. But the effectiveness of adjusting the compression characteristics of wide-dynamic-range compression hearing aids-the compression ratios, the variation of compression ratio with level, and the threshold of compression-to restore normal loudness growth for the individual patient has never been properly tested; individual loudness measurements have been too uncertain to permit meaningful individual adjustments. Recent investigators have reported standard deviations of such measurements in normal-hearing subjects of 6.4 dB and 7.8 dB. This investigation describes a method of measuring loudness function with a standard deviation in normal-hearing subjects of the order of 1 dB, both significantly lower than that of previous methods and sufficiently accurate for individual-subject adjustments. DESIGN: Each of nine normal-hearing subjects-seven of them inexperienced and one a 9-year-old was asked to make three successive loudness trisections within an amplitude range of 40 to 80 dB SPL, providing six points from which to plot a loudness-function curve between these limits. The individual and average curves were validated as accurate loudness functions by comparing them to the curve defined by the equation of loudness versus amplitude in current Standards. In a second validation experiment, the loudness functions of masked ears measured by trisection were compared to the loudness function of those ears measured by loudness balance between masked and unmasked ears. RESULTS: The difference between a loudness function based on the average of subject trisections and the loudness function defined by the ANSI Standard loudness equation was -1.92 dB at the lowest trisection level and +0.05 dB at the highest level. The standard deviations of subject responses were 1.63 dB for the lowest trisection level and 0.68 dB for the highest level, with an average of 1.1 dB. The across-subject standard deviation of the test-retest differences for three subjects was less than 1.7 dB for the first three lower level responses and less than 0.8 dB for the remaining three responses. CONCLUSIONS: A trisection procedure for measuring loudness function showed validity and significantly less variation than previous loudness-measurement procedures. Such a procedure, once it has been validated for hearing-impaired subjects, makes it possible to test hearing aid design and fitting strategies that are based on individual-patient loudness functions.

Ranking hearing aid input-output functions for understanding low-, conversational-, and high-level speech in multitalker babble.

PURPOSE: To determine the rankings of 6 input-output functions for understanding low-level, conversational, and high-level speech in multitalker babble without manipulating volume control for listeners with normal hearing, flat sensorineural hearing loss, and mildly sloping sensorineural hearing loss. METHOD: Peak clipping, compression limiting, and 4 wide dynamic range compression (WDRC) input-output functions were compared in a repeated-measure design. Interactions among the compression characteristics were minimized. Speech and babble were processed and recorded at 3 input levels: 45, 65, and 90 dB sound pressure level. Speech recognition of 3 groups of listeners (n = 6/group) was tested for speech processed by each input-output function and at each input level. RESULTS: Input-output functions that made low-level speech audible and high-level speech less distorted by avoiding peak clipping or severe compression yielded higher speech recognition scores. These results are consistent with previous findings in the literature. CONCLUSION: WDRCs with the low compression ratio region extended to a high input level or with a high compression limiting threshold were the best for speech recognition in babble when the hearing aid user cannot or does not want to manipulate the volume control. Future studies on subjective preferences of different input-output functions are needed.

Validation of the Home Hearing Test™.

BACKGROUND: The Home Hearing Test™ (HHT) is an automated pure-tone threshold test that obtains an air-conduction audiogram at five test frequencies. It was developed to provide increased access to hearing testing and support home telehealth programs. PURPOSE: The study was conducted as part of an audiology telehealth trial based at the U.S. Department of Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN. Air-conduction audiograms obtained by the HHT were compared to results obtained in the clinic. RESEARCH DESIGN: Prospective, repeated measures. STUDY SAMPLE: Twenty-eight participants, aged 44-88 yr (mean = 65) were recruited from the Nashville U.S. Department of Veterans Affairs audiology clinic. Participants were required to have a Windows personal computer in the home and were self-reported to be comfortable with using computers. Two participants had normal hearing and 26 had hearing loss of various severities and configurations. DATA COLLECTION AND ANALYSIS: Audiograms were obtained in the audiology clinic by experienced audiologists following standard clinical protocols. Participants were provided with a kit for installing HHT on their home computers. The HHT air-conduction audiogram is obtained with Automated Method for Testing Auditory Sensitivity (AMTAS(®)), described in previous publications. Threshold pairs (clinic versus HHT) were analyzed by determining distributions of threshold differences and absolute differences. These were compared to distributions of differences between manual threshold pairs obtained by two audiologists and AMTAS(®) versus manual threshold pairs obtained under laboratory conditions. RESULTS: Threshold differences (clinic versus HHT) were slightly larger than differences between thresholds obtained by two audiologists and AMTAS(®) versus manual threshold differences obtained under laboratory conditions. The differences were not statistically significant. CONCLUSIONS: HHT air-conduction audiograms agree well with audiograms obtained in the clinic. HHT is well suited to home telehealth applications and personal use.

Fitting hearing aids using clinical prefitting speech measures: an evidence-based review.

A systematic review of the literature addressed the question "Is there evidence of a good correlation between unaided prefitting speech measures and aided satisfaction on self-report measures?" This restricted question is only one of several possible questions related to speech measures and hearing aid fittings. The levels of evidence that were accepted included meta-analyses, randomized controlled trials, and nonrandomized intervention studies. Nearly 300 articles and book chapters were identified during the initial search; 220 were eliminated on the basis of their abstracts; and 80 papers and book chapters were reviewed in depth. Five studies met the criteria set forth in this review. No significant correlation between traditional unaided prefitting speech measures and aided satisfaction was found in any of the five studies. One of the studies showed a correlation between the results of a prefitting speech-in-noise test and self-reported aided satisfaction.

Performance of directional microphones for hearing aids: real-world versus simulation.

The purpose of this study was to assess the accuracy of clinical and laboratory measures of directional microphone benefit. Three methods of simulating a noisy restaurant listening situation ([1] a multimicrophone/multiloudspeaker simulation, the R-SPACE, [2] a single noise source behind the listener, and [3] a single noise source above the listener) were evaluated and compared to the "live" condition. Performance with three directional microphone systems differing in polar pattern (omnidirectional, supercardioid, and hypercardioid array) and directivity indices (0.34, 4.20, and 7.71) was assessed using a modified version of the Hearing in Noise Test (HINT). The evaluation revealed that the three microphones could be ordered with regard to the benefit obtained using any of the simulation techniques. However, the absolute performance obtained with each microphone type differed among simulations. Only the R-SPACE simulation yielded accurate estimates of the absolute performance of all three microphones in the live condition. Performance in the R-SPACE condition was not significantly different from performance in the "live restaurant" condition. Neither of the single noise source simulations provided accurate predictions of real-world (live) performance for all three microphones.

Factors influencing use of hearing protection by trumpet players.

Although a great many brass players, and trumpet players in particular, successfully use high-fidelity earplugs, others report problems with their use. This article discusses factors that may discourage a brass player from using hearing protection: These include (a) a lack of acclimatization time; (b) a loss of "fortissimo blare" from the aural distortion generated by the 110- to 120-dB SPL produced at the open ear with fortissimo playing; (c) a shallow earmold seal, leading to a large occlusion effect; (d) a poor seal combined with incorrect acoustic mass in the sound channel; and (e) hearing loss where many harmonic overtones of even moderately loud playing may become inaudible with earplugs to a lifelong trumpet player with high-frequency hearing loss. The limitations imposed by each of these can usually be overcome with modifications of the hearing protection device (HPD) or with acclimatization time, allowing a lifetime of playing without the all-too-common "musicians' hearing loss" and/or tinnitus. A review of these factors helps to delineate some of the perceptual issues that musicians may have with any change in the spectrum of their instrument-whether it is related to attenuation or amplification.

Development of a quick speech-in-noise test for measuring signal-to-noise ratio loss in normal-hearing and hearing-impaired listeners.

This paper describes a shortened and improved version of the Speech in Noise (SIN) Test (Etymotic Research, 1993). In the first two of four experiments, the level of a female talker relative to that of four-talker babble was adjusted sentence by sentence to produce 50% correct scores for normal-hearing subjects. In the second two experiments, those sentences-in-babble that produced either lack of equivalence or high across-subject variability in scores were discarded. These experiments produced 12 equivalent lists, each containing six sentences, with one sentence at each adjusted signal-to-noise ratio of 25, 20, 15, 10, 5, and 0 dB. Six additional lists were also made equivalent when the scores of particular pairs were averaged. The final lists comprise the "QuickSIN" test that measures the SNR a listener requires to understand 50% of key words in sentences in a background of babble. The standard deviation of single-list scores is 1.4 dB SNR for hearing-impaired subjects, based on test-retest data. A single QuickSIN list takes approximately one minute to administer and provides an estimate of SNR loss accurate to +/-2.7 dB at the 95% confidence level.