Speech-clarity judgments of hearing-aid-processed speech in noise: Differing polar patterns and acoustic environments

This investigation assessed the extent to which listeners’ preferences for hearing aid microphone polar patterns vary across listening environments, and whether normal-hearing and inexperienced and experienced hearing-impaired listeners differ in such preferences. Paired-comparison judgments of speech clarity (i.e. subjective speech intelligibility) were made monaurally for recordings of speech in noise processed by a commercially available hearing aid programmed with an omnidirectional and two directional polar patterns (cardioid and hypercardioid). Testing environments included a sound-treated room, a living room, and a classroom. Polar-pattern preferences were highly reliable and agreed closely across all three groups of listeners. All groups preferred listening in the sound-treated room over listening in the living room, and preferred listening in the living room over listening in the classroom. Each group preferred the directional patterns to the omnidirectional pattern in all room conditions. We observed no differences in preference judgments between the two directional patterns or between hearing-impaired listeners’ extent of amplification experience. Overall, findings indicate that listeners perceived qualitative benefits from microphones having directional polar patterns.     

The robustness of hearing aid microphone preferences in everyday listening environments

Automatic directionality algorithms currently implemented in hearing aids assume that hearing-impaired persons with similar hearing losses will prefer the same microphone processing mode in a specific everyday listening environment. The purpose of this study was to evaluate the robustness of microphone preferences in everyday listening. Two hearing-impaired persons made microphone preference judgments (omnidirectional preferred, directional preferred, no preference) in a variety of everyday listening situations. Simultaneously, these acoustic environments were recorded through the omnidirectional and directional microphone processing modes. The acoustic recordings were later presented in a laboratory setting for microphone preferences to the original two listeners and other listeners who differed in hearing ability and experience with directional microphone processing. The original two listeners were able to replicate their live microphone preferences in the laboratory with a high degree of accuracy. This suggests that the basis of the original live microphone preferences were largely represented in the acoustic recordings. Other hearing-impaired and normal-hearing participants who listened to the environmental recordings also accurately replicated the original live omnidirectional preferences; however, directional preferences were not as robust across the listeners. When the laboratory rating did not replicate the live directional microphone preference, listeners almost always expressed no preference for either microphone mode. Hence, a preference for omnidirectional processing was rarely expressed by any of the participants to recorded sites where directional processing had been preferred as a live judgment and vice versa. These results are interpreted to provide little basis for customizing automatic directionality algorithms for individual patients. The implications of these findings for hearing aid design are discussed.     

Comparison of performance across three directional hearing aids

This study compared the speech recognition performance of 12 hearing-impaired listeners fit with three commercially available behind-the-ear hearing aids in both directional and omnidirectional modes. One digitally programmable analog and two "true digital" hearing aids were selected as test instruments. Testing was completed in both "living room" and anechoic room environments. Speech recognition was examined using modified forms of the Hearing in Noise Test and the Nonsense Syllable Test. The single competing stimuli of these tests were replaced with five uncorrelated competing sources. Results revealed a significant speech recognition in noise advantage for all directional hearing aids in comparison to their omnidirectional counterparts. Maximum performance of the directional hearing aids did not significantly vary across circuit type, suggesting that processing differences did not affect maximum directional hearing aid performance. In addition, the results suggest that performance in one reverberant environment cannot be used to accurately predict performance in an environment with differing reverberation.     

Predicting directional hearing aid benefit for individual listeners

The fitting of directional microphone hearing aids is becoming increasingly more routine, and this fitting option has proven to be a successful method to improve speech intelligibility in many noisy listening environments. Data suggest, however, that some hearing-impaired listeners receive significantly more directional benefit than others. It is of interest, therefore, to determine if directional benefit is predictable from identifiable audiologic factors. In this report, we examined whether the slope of audiometric configuration, amount of high-frequency hearing loss, and/or the aided omnidirectional performance for a speech-in-noise intelligibility task could be used to predict the magnitude of directional hearing aid benefit. Overall results obtained from three separate investigations revealed no significant correlation between the slope of audiometric configuration or amount of high-frequency hearing loss and the benefit obtained from directional microphone hearing instruments. Although there was a significant, negative relationship between aided omnidirectional performance and the directional benefit obtained in one study, there was considerable variability among individual participants, and nearly all of the listeners with the best omnidirectional hearing aid performance still received significant additional benefit from directional amplification. These results suggest that audiologists should consider the use of directional amplification for patients regardless of audiogram slope, high-frequency hearing loss, or omnidirectional speech intelligibility score.     

Predicting hearing aid microphone preference in everyday listening

Seventeen hearing-impaired adults were fit with omnidirectional/directional hearing aids, which they wore during a four-week trial. For each listening situation encountered in daily living during a total of seven days, participants selected the preferred microphone mode and described the listening situation in terms of five environmental variables, using a paper and pencil form. Results indicated that hearing-impaired adults typically spend the majority of their active listening time in situations with background noise present and surrounding the listener, and the signal source located in front and relatively near. Microphone preferences were fairly evenly distributed across listening situations but differed depending on the characteristics of the listening environment. The omnidirectional mode tended to be preferred in relatively quiet listening situations or, in the presence of background noise, when the signal source was relatively far away. The directional mode tended to be preferred when background noise was present and the signal source was located in front of and relatively near the listener. Results suggest that knowing only signal location and distance and whether background noise is present or absent, omnidirectional/directional hearing aids can be set in the preferred mode in most everyday listening situations. These findings have relevance for counseling patients when to set manually switchable omnidirectional/directional hearing aids in each microphone mode, as well as for the development of automatic algorithms for selecting omnidirectional versus directional microphone processing.     

The impact of head angle on monaural and binaural performance with directional and omnidirectional hearing aids

OBJECTIVE: To evaluate the impact of head turn and monaural and binaural fittings on the sentence reception thresholds of hearing-impaired listeners wearing directional and omnidirectional hearing aids. DESIGN: Sentence reception thresholds were measured for 20 listeners fit monaurally and binaurally with behind-the-ear hearing aids set in both directional and omnidirectional modes. All listeners exhibited symmetrical, sloping, sensorineural hearing loss. The aided performance across these four fittings was evaluated for three different head and body angles. The three angles reflected body turns of 0 degrees, 15 degrees, and 30 degrees as measured relative to the primary sound source, with 0 degrees denoting the listener directly facing the sound source. Listeners were instructed to keep their heads in a fixed horizontal position and turn their heads and bodies to face visual targets at the three test angles. Sentences from the Hearing in Noise Test presented with a background of five, spatially separated, uncorrelated samples of cafeteria noise served as test material. All testing was performed in a moderately reverberant (Rt = 631 msec) "living room" environment. RESULTS: Participants generally performed significantly better when fit with directional versus omnidirectional hearing aids, and when fit binaurally versus monaurally across test conditions. The measured "binaural advantage" was reduced with increasing head angle. Participants performed significantly better with a 30 degree head angle than when directly facing the primary speaker. This "head turn advantage" was most prominent for monaural (versus binaural) conditions. Binaural and head turn advantages were not significantly different across directional and omnidirectional modes. CONCLUSIONS: These data provide additional support for the use of directional hearing aids and binaural amplification to improve speech intelligibility in noisy environments. The magnitude of these advantages was similar to that reported in previous investigations. The data also showed that hearing aid wearers achieved significantly better speech intelligibility in noise by turning their heads and bodies to a position in which they were not directly facing the sound source. This head turn advantage was in good agreement with the increase in Directivity Index with head turn and reflected the fact that hearing aids are generally most sensitive to sounds arriving from angles other than directly in front of the hearing aid wearer. Although these data suggest that many monaural hearing aid wearers may significantly improve speech intelligibility in noise through the use of head turn, the interaction between this advantage and the potential loss of visual cues with head turn is unknown.     

Noise reduction results of an adaptive filtering technique for dual-microphone behind-the-ear hearing aids

OBJECTIVE: The performance of an adaptive beam-former in a 2-microphone, behind-the-ear hearing aid for speech understanding in noisy environments was evaluated. Physical and perceptual evaluations were carried out. This was the first large-scale test of a wearable real-time implementation of this algorithm. The main perceptual research questions of this study were related to the influence on the noise reduction performance of (1) the spectro-temporal character of the jammer sound, (2) the jammer sound scene, (3) hearing impairment, and (4) the basic microphone configuration in the hearing aid. Four different speech materials were used for the perceptual evaluations. All tests were carried out in an acoustical environment comparable to living room reverberation. DESIGN: The adaptive beamformer was implemented in Audallion, a small, body-worn processor, linked to a Danasound 2-microphone behind-the-ear aid. The strategy was evaluated physically in different acoustical environments. Using speech reception threshold (SRT) measurements, the processing was evaluated perceptually and the different research questions addressed with three groups of subjects. Groups I, II, and III consisted of 10 normal-hearing, 5 hearing-impaired, and 7 normal-hearing persons, respectively. The tests were carried out in three spectro-temporally different jammer sounds (unmodulated and modulated speech weighted noise, multitalker babble) and in three different noise scenarios (single noise source at 90 degrees, noise sources at 90 degrees and 270 degrees relative to speaker position, diffuse noise scene). Two microphone configurations were compared: a device equipped with two omnidirectional microphones and a device equipped with one hardware directional and one omnidirectional microphone. In each of these conditions, the adaptive beamformer and the directional and omnidirectional microphone configurations were tested. RESULTS: The improvement in signal-to-noise ratio from the use of the adaptive beamformer did not depend on the spectro-temporal character of the jammer sounds and the speech materials used, although the absolute levels of the SRTs varied appreciably for different speech-noise combinations. The performance of the adaptive noise reduction depended on the jammer sound scene. CONCLUSIONS: No difference in signal-to-noise ratio improvement was observed between hearing-impaired and normal-hearing listeners, although individual SRT levels may differ. On average, an SRT improvement of 7.7 and 3.9 dB for a single noise source at 90 degrees and 5.9 and 3.4 dB for two noise sources at 90 degrees and 270 degrees was obtained for both normal-hearing and hearing-impaired listeners, using the adaptive beamformer and the directional microphone, respectively, relative to the omnidirectional microphone signal. In diffuse noise, only small improvements were obtained.     

Relationship between laboratory measures of directional advantage and everyday success with directional microphone hearing aids

The improvement in speech recognition in noise obtained with directional microphones compared to omnidirectional microphones is referred to as the directional advantage. Laboratory studies have revealed substantial differences in the magnitude of the directional advantage across hearing-impaired listeners. This investigation examined whether persons who were successful users of directional microphone hearing aids in everyday living tended to obtain a larger directional advantage in the test booth than persons who were unsuccessful users. Results revealed that the mean directional advantage did not differ significantly between patients who used the directional mode regularly and those who reported little or no benefit from directional microphones in daily living and, therefore, tended to leave their hearing aids set in the default omnidirectional mode. Success with directional microphone hearing aids in everyday living, therefore, cannot be reliably predicted by the magnitude of the directional advantage obtained in the clinic.     

Evaluation of an adaptive,directional-microphone hearing aid

The effectiveness of adaptive directional processing for improvement of speech recognition in comparison to non-adaptive directional and omni-directional processing was examined across four listening environments intended to simulate those found in the real world. The test environment was a single, moderately reverberant room with four loudspeaker configurations: three with fixed discrete noise source positions and one with a single panning noise source. Sentence materials from the Hearing in Noise Test (HINT) and Connected Speech Test (CST) were selected as test materials. Speech recognition across all listening conditions was evaluated for 20 listeners fitted binaurally with Phonak Claro behind-the-ear (BTE) style hearing aids. Results indicated improved speech recognition performance with adaptive and non-adaptive directional processing over that measured with the omnidirectional processing across all four listening conditions. While the magnitudes of directional benefit provided to subjects listening in adaptive and fixed directional modes were similar in some listening environments, a significant speech recognition advantage was measured for the adaptive mode in specific conditions. The advantage for adaptive over fixed directional processing was most prominent when a competing noise was presented from the listener's sides (both fixed and panning noise conditions), and was partially predictable from electroacoustically measured directional pattern data.     

Hearing-in-Noise: comparison of listeners with normal and (aided) impaired hearing

In this study, the performance of 48 listeners with normal hearing was compared to the performance of 46 listeners with documented hearing loss. Various conditions of directional and omnidirectional hearing aid use were studied. The results indicated that when the noise around a listener was stationary, a first- or second-order directional microphone allowed a group of hearing-impaired listeners with mild-to-moderate, bilateral, sensorineural hearing loss to perform similarly to normal hearing listeners on a speech-in-noise task (i.e., they required the same signal-to-noise ratio to achieve 50% understanding). When the noise source was moving around the listener, only the second-order (three-microphone) system set to an adaptive directional response (where the polar pattern changes due to the change in noise location) allowed a group of hearing-impaired individuals with mild-to-moderate sensorineural hearing loss to perform similarly to young, normal-hearing individuals.     

Full time directional versus user selectable microphone modes in hearing aids

OBJECTIVE: The purpose of this experiment was to systematically examine hearing aid benefit as measured by speech recognition and self-assessment methods across omnidirectional and directional hearing aid modes. These data were used to compare directional benefit as measured by speech recognition in the laboratory to hearing aid wearer's perceptions of benefit in everyday environments across full-time directional, full-time omnidirectional, and user selectable directional fittings. Identification of possible listening situations that resulted in different self reported hearing aid benefit as a function of microphone type was a secondary objective of this experiment. DESIGN: Fifteen adults with symmetrical, sloping sensorineural hearing loss were fitted bilaterally with in-the-ear (ITE) directional hearing aids. Measures of hearing aid benefit included the Profile of Hearing Aid Benefit (PHAB), the Connected Sentence Test (CST), the Hearing in Noise Test (HINT), and a daily use log. Additionally, two new subscales were developed for administration with the PHAB. These subscales were developed to specifically address situations in which directional hearing aids may provide different degrees of benefit than omnidirectional hearing aids. Participants completed these measures in three conditions: omnidirectional only (O), directional only with low-frequency gain compensation (D), and user-selectable directional/omnidirectional (DO). RESULTS: Results from the speech intelligibility in noise testing indicated significantly more hearing aid benefit in directional modes than omnidirectional. PHAB results indicated more benefit on the background noise subscale (BN) in the DO condition than in the O condition; however, this directional advantage was not present for the D condition. Although the reliability of the newly proposed subscales is as yet unknown, the data were interpreted as revealing a directional advantage in situations where the signal of interest was in front of the participant and a directional disadvantage in situations where the signal of interest was behind the listener or localization was required. CONCLUSIONS: Laboratory directional benefit is reflected in self-assessment measures that focus on listening in noise when the sound source of interest is in front of the listener. The use of a directional hearing aid mode; however, may have either a positive, a neutral, or a negative impact on hearing aid benefit measured in noisy situations, depending on the specific listening situation.     

Better speech perception in noise with an assistive multimicrophone array for hearing AIDS

OBJECTIVE: To evaluate the improvement in speech intelligibility in noise obtained with an assistive real-time fixed endfire array of bidirectional microphones in comparison with an omnidirectional hearing aid microphone in a realistic environment. DESIGN: The microphone array was evaluated physically in anechoic and reverberant conditions. Perceptual tests of speech intelligibility in noise were carried out in a reverberant room, with two types of noise and six different noise scenarios with single and multiple noise sources. Ten normal-hearing subjects and 10 hearing aid users participated. The speech reception threshold for sentences was measured in each test setting for the omnidirectional microphone of the hearing aid and for the hearing aid in combination with the array with one and three active microphones. In addition, the extra improvement of five active array microphones, relative to three, was determined in another group of 10 normal-hearing listeners. RESULTS: Improvements in speech intelligibility in noise obtained with the array relative to an omnidirectional microphone depend on noise scenario and subject group. Improvements up to 12 dB for normal-hearing and 9 dB for hearing-impaired listeners were obtained with three active array microphones relative to an omnidirectional microphone for one noise source at 90 degrees . For three uncorrelated noise sources at 90 degrees, 180 degrees, and 270 degrees, improvements of approximately 9 dB and 6 dB were obtained for normal-hearing and hearing-impaired listeners, respectively. Even with a single noise source at 45 degrees, benefits of 4 dB were achieved in both subject groups. Five active microphones in the array can provide an additional improvement at 45 degrees of approximately 1 dB, relative to the three-microphone configuration for normal-hearing listeners. CONCLUSIONS: These improvements in signal-to-noise ratio can be of great benefit for hearing aid users, who have difficulties with speech understanding in noisy environments.     

Distance and reverberation effects on directional benefit

OBJECTIVE: Understanding the potential benefits and limitations of directional hearing aids across a wide range of listening environments is important when counseling persons with hearing loss regarding realistic expectations for these devices. The purpose of this study was to examine the impact of speaker-to-listener distance on directional benefit in two reverberant environments, in which the dominate noise sources were placed close to the hearing aid wearer. In addition, speech transmission index (STI) measures made in the test environments were compared to measured sentence recognition to determine if performance was predictable across changes in distance, reverberation and microphone mode. DESIGN: The aided sentence recognition, in noise, for fourteen adult participants with symmetrical sensorineural hearing impairment was measured in six environmental conditions in both directional and omnidirectional modes. A single room, containing four uncorrelated noise sources served as the test environment. The room was modified to exhibit either low (RT60 = 0.3 sec) or moderate (RT60 = 0.9 sec) levels of reverberation. Sentence recognition was measured in both reverberant environments at three different speech loudspeaker-to-listener distances (1.2 m, 2.4 m, and 4.8 m). STI measures also were made in each of the 12 listening conditions (2 microphone modes x 3 distances x 2 reverberation environments). RESULTS: A decrease in directional benefit was measured with increasing distance in the moderate reverberation condition. Although reduced, directional benefit was still present in the moderately reverberant environment at the farthest speech speaker-to-listener distance tested in this experiment. A similar decrease with increasing speaker-to-listener distance was not measured in the low reverberation condition. The pattern of average sentence recognition results across varying distances and two different reverberation times agreed with the pattern of STI values measured under the same conditions. CONCLUSIONS: Although these data support increased directional benefit in noise for reduced speaker-to-listener distance, some benefit was still obtained by listeners when listening beyond "effective" critical distance under conditions of low (300 msec) to moderate (900 msec) reverberation. It is assumed that the directional benefit was due to the reduction of the direct sound energy from the noise sources near the listener. The use of aided STI values for the prediction of average word recognition across listening conditions that differ in reverberation, microphone directivity, and speaker-to-listener distance also was supported.     

Effect of signal-to-noise ratio on directional microphone benefit and preference

This study examined speech intelligibility and preferences for omnidirectional and directional microphone hearing aid processing across a range of signal-to-noise ratios (SNRs). A primary motivation for the study was to determine whether SNR might be used to represent distance between talker and listener in automatic directionality algorithms based on scene analysis. Participants were current hearing aid users who either had experience with omnidirectional microphone hearing aids only or with manually switchable omnidirectional/directional hearing aids. Using IEEE/Harvard sentences from a front loudspeaker and speech-shaped noise from three loudspeakers located behind and to the sides of the listener, the directional advantage (DA) was obtained at 11 SNRs ranging from -15 dB to +15 dB in 3 dB steps. Preferences for the two microphone modes at each of the 11 SNRs were also obtained using concatenated IEEE sentences presented in the speech-shaped noise. Results revealed that a DA was observed across a broad range of SNRs, although directional processing provided the greatest benefit within a narrower range of SNRs. Mean data suggested that microphone preferences were determined largely by the DA, such that the greater the benefit to speech intelligibility provided by the directional microphones, the more likely the listeners were to prefer that processing mode. However, inspection of the individual data revealed that highly predictive relationships did not exist for most individual participants. Few preferences for omnidirectional processing were observed. Overall, the results did not support the use of SNR to estimate the effects of distance between talker and listener in automatic directionality algorithms.     

An objective measure for selecting microphone modes in OMNI/DIR hearing aid circuits

OBJECTIVES: Studies have shown that listener preferences for omnidirectional (OMNI) or directional (DIR) processing in hearing aids depend largely on the characteristics of the listening environment, including the relative locations of the listener, signal sources, and noise sources; and whether reverberation is present. Many modern hearing aids incorporate algorithms to switch automatically between microphone modes based on an analysis of the acoustic environment. Little work has been done, however, to evaluate these devices with respect to user preferences, or to compare the outputs of different signal processing algorithms directly to make informed choices between the different microphone modes. This study describes a strategy for automatically switching between DIR and OMNI microphone modes based on a direct comparison between acoustic speech signals processed by DIR and OMNI algorithms in the same listening environment. In addition, data are shown regarding how a decision to choose one microphone mode over another might change as a function of speech to noise ratio (SNR) and spatial orientation of the listener. DESIGN: Speech and noise signals were presented at a variety of SNR's and in different spatial orientations relative to a listener's head. Monaural recordings, made in both OMNI and DIR microphone processing modes, were analyzed using a model of auditory processing that highlights the spectral and temporal dynamics of speech. Differences between OMNI and DIR processing were expressed in terms of a modified spectrotemporal modulation index (mSTMI) developed specifically for this hearing aid application. Differences in mSTMI values were compared with intelligibility measures and user preference judgments made under the same listening conditions. RESULTS: A comparison between the results of the mSTMI analyses and behavioral data (intelligibility and preference judgments) showed excellent agreement, especially in stationary noise backgrounds. In addition, the mSTMI was found to be sensitive to changes in SNR as well as spatial orientation of the listener relative to signal and noise sources. Subsequent mSTMI analyses on hearing aid recordings obtained from real-life environments with more than one talker and modulated noise backgrounds also showed promise for predicting the preferred microphone setting in varied and complex listening environments.     

Advantages of Binaural Amplification to Acceptable Noise Level of Directional Hearing Aid Users

Objectives

The goal of the present study was to examine whether Acceptable Noise Levels (ANLs) would be lower (greater acceptance of noise) in binaural listening than in monaural listening condition and also whether meaningfulness of background speech noise would affect ANLs for directional microphone hearing aid users. In addition, any relationships between the individual binaural benefits on ANLs and the individuals'' demographic information were investigated.

Methods

Fourteen hearing aid users (mean age, 64 years) participated for experimental testing. For the ANL calculation, listeners'' most comfortable listening levels and background noise level were measured. Using Korean ANL material, ANLs of all participants were evaluated under monaural and binaural amplification with a counterbalanced order. The ANLs were also compared across five types of competing speech noises, consisting of 1- through 8-talker background speech maskers. Seven young normal-hearing listeners (mean age, 27 years) participated for the same measurements as a pilot testing.

Results

The results demonstrated that directional hearing aid users accepted more noise (lower ANLs) with binaural amplification than with monaural amplification, regardless of the type of competing speech. When the background speech noise became more meaningful, hearing-impaired listeners accepted less amount of noise (higher ANLs), revealing that ANL is dependent on the intelligibility of the competing speech. The individuals'' binaural advantages in ANLs were significantly greater for the listeners with longer experience of hearing aids, yet not related to their age or hearing thresholds.

Conclusion

Binaural directional microphone processing allowed hearing aid users to accept a greater amount of background noise, which may in turn improve listeners'' hearing aid success. Informational masking substantially influenced background noise acceptance. Given a significant association between ANLs and duration of hearing aid usage, ANL measurement can be useful for clinical counseling of binaural hearing aid candidates or unsuccessful users.     

Speech recognition ability of children with unilateral sensorineural hearing loss as a function of amplification, speech stimuli and listening condition

The purpose of this investigation was to examine three types of audiological recommendations [unaided, CROS (contralateral routing of signals) and personal FM system] and their impact upon speech recognition ability of children with unilateral sensorineural hearing loss. Each of these recommendations was tested under three listening conditions encountered in a classroom [monaural direct (MD), monaural indirect (MI), midline signal/omnidirectional noise (MS/ON)] with two types of speech materials (Nonsense Syllable Test and an American English adaptation on the Bamford-Kowal-Bench Sentence Lists). These experimental conditions were simulated in a classroom, recorded on audiotape, and played back to subjects under headphones to control such factors as signal-to-noise ratio, earmold fit, and head shadow effects. Six school-age children with unilateral hearing losses between 56 and greater than 120 dB HL (PTA) were evaluated using a repeated measures design. The children experienced the most listening difficulty in the MI condition when they were unaided. The CROS aid improved speech recognition in this condition but degraded speech recognition in the MD condition. The FM system was the only audiological recommendation to produce uniformly high speech recognition scores across all listening conditions with both types of speech materials. Implications for the audiological management of unilaterally hearing-impaired children in the classroom are discussed.     

Loudness judgment procedures for evaluating hearing aid preselection decisions for severely and profoundly hearing-impaired listeners.

Hearing aid fitting involves a two-phase process of preselection and evaluation (Seewald RC and Ross M. Amplification for the Hearing Impaired 1988:213-271). The purpose of the present study was to examine alternative procedures that clinicians might use in the evaluation phase to verify the adequacy of hearing aid preselection decisions for severely and profoundly hearing-impaired listeners. Bekesy tracking, loudness rating, and conventional bracketing procedures were used to determine threshold, most comfortable listening level, and uncomfortable listening level for 10 hearing-impaired young adults. Stimuli were pulsed pure tones of 500, 1000, and 2000 Hz and filtered words. Means and standard deviations of most comfortable listening levels and uncomfortable listening levels derived from loudness judgments of the 10 subjects showed only nominal differences across procedures. However, correlation analysis (Pearson r) indicated that individuals responded to the three procedures in varying ways, producing different loudness judgments and overall dynamic ranges. Thus, test procedure may influence the clinician's final evaluation of a preselected hearing aid. Initial work suggests that closed-set response categories such as loudness rating can limit measurement variability and potentially guide the clinician's evaluation of hearing aid preselection decisions.     

Low-frequency gain compensation in directional hearing aids

Hearing aids currently available on the market with both omnidirectional and directional microphone modes often have reduced amplification in the low frequencies when in directional microphone mode due to better phase matching. The effects of this low-frequency gain reduction for individuals with hearing loss in the low frequencies was of primary interest. Changes in sound quality for quiet listening environments following gain compensation in the low frequencies was of secondary interest. Thirty participants were fit with bilateral in-the-ear hearing aids, which were programmed in three ways while in directional microphone mode: no-gain compensation, adaptive-gain compensation, and full-gain compensation. All participants were tested with speech in noise tasks. Participants also made sound quality judgments based on monaural recordings made from the hearing aid. Results support a need for gain compensation for individuals with low-frequency hearing loss of greater than 40 dB HL.