Bilateral Hearing Aid Fitting Research Articles

Effectiveness of an Over-the-Counter Self-fitting Hearing Aid Compared With an Audiologist-Fitted Hearing Aid

Hearing loss is a highly prevalent condition, with numerous debilitating consequences when left untreated. However, less than 20% of US adults with hearing loss use hearing aids. Over-the-counter (OTC) hearing aids became available in October 2022 to improve access and affordability. However, clinical effectiveness studies of available OTC hearing aids using the existing devices in the market are limited. To compare the clinical effectiveness of a self-fitting OTC hearing aid with remote support and a hearing aid fitted using audiologist-fitted best practices. This randomized clinical effectiveness trial was conducted between April 14 and August 29, 2022. Sixty-eight adults with self-perceived mild to moderate hearing loss were recruited and randomly assigned to either the self-fitting or the audiologist-fitted group. Following bilateral hearing aid fitting, participants first completed a 2-week, take-home field trial without any support. Access to fine-tuning for both groups was only available after the 2-week trial. Support and adjustment were provided remotely for the self-fitting group per request and by the audiologist for the audiologist-fitted group. Participants were then reassessed after an additional 4-week take-home trial. A commercially available self-fitting OTC hearing aid was provided to participants in the self-fitting group who were expected to set up the hearing aids using the commercially supplied instructional material and accompanying smartphone application. In the audiologist-fitted group, audiologists fitted the same hearing aid according to the National Acoustics Laboratories nonlinear version 2 algorithm for prescriptive gain target using real-ear verification with hearing aid use instruction. The primary outcome measure was self-reported hearing aid benefit, measured using the Abbreviated Profile of Hearing Aid Benefit (APHAB). Secondary measures included the International Outcome Inventory for Hearing Aids (IOI-HA) and speech recognition in noise measured using an abbreviated speech-in-noise test and a digits-in-noise test. All measures were completed at baseline and at 2 intervals following hearing aid fitting (2 and 6 weeks). Sixty-four participants were included in the analytic sample (33 men [51.6%]; mean [SD] age, 63.6 [14.1] years), with equal numbers of participants (n = 32) randomized into each group. The groups did not differ significantly in age (effect size r = -0.2 [95% CI, -0.3 to 0.2]) or 4-frequency pure-tone average (effect size r = 0.2 [95% CI, -0.1 to 0.4]). After the 2-week field trial, the self-fitting group had an initial advantage compared with the audiologist-fitted group on the self-reported APHAB (Cohen d = -0.5 [95% CI, -1.0 to 0]) and IOI-HA (effect size r = 0.3 [95% CI, 0.0-0.5]) but not speech recognition in noise. At the end of the 6-week trial, no meaningful differences were evident between the groups on any outcome measures. In this randomized clinical effectiveness trial, self-fitting OTC hearing aids with remote support yielded outcomes at 6 weeks post fitting comparable to those of hearing aids fitted using audiologist best practices. These findings suggest that self-fitting OTC hearing aids may provide an effective intervention for mild to moderate hearing loss. ClinicalTrials.gov Identifier: NCT05337748.

Determining unilateral or bilateral hearing aid preference in adults: a prospective study

Objective Despite high rates of bilateral hearing aid fitting globally, a number of adults continue to reject one hearing aid. The current study aimed to identify a clinically suitable tool for determining, pre-fitting, which clients might prefer one hearing aid. Study Sample: Ninety-five new adult hearing aid candidates, aged 49–87 years, were assessed prior to a first hearing aid fitting. Sixty-eight participants adhered to the prescribed protocol for both bilateral and unilateral hearing aid use. Design Performance was assessed on a modified version of the Listening in Spatialised Noise – Sentences test (LiSN-S), the Dichotic Digits difference Test, the Experiential Hearing Aid simulator, and the Grooved Pegboard Test. All participants were fitted bilaterally, but were instructed to alternate between unilateral and bilateral hearing aid use over fourteen weeks post-fitting. Participants’ wearing preferences were assessed via a short questionnaire. Results 78% of participants expressed an overall preference for bilateral hearing aid use. Only the LiSN-S bilateral advantage test outcomes significantly correlated with overall wearing preference. Conclusions Although the LiSN-S bilateral advantage score related to overall wearing preference, the accuracy of the predictor was too low to warrant implementation of this test prior to hearing aid fitting. The current practice of recommending bilateral hearing aid use continues to be the best option for clinicians.

Effects of directional hearing aid settings on different laboratory measures of spatial awareness perception.

Hearing loss can negatively influence the spatial hearing abilities of hearing-impaired listeners, not only in static but also in dynamic auditory environments. Therefore, ways of addressing these deficits with advanced hearing aid algorithms need to be investigated. In a previous study based on virtual acoustics and a computer simulation of different bilateral hearing aid fittings, we investigated auditory source movement detectability in older hearing- impaired (OHI) listeners. We found that two directional processing algorithms could substantially improve the detectability of left-right and near-far source movements in the presence of reverberation and multiple interfering sounds. In the current study, we carried out similar measurements with a loudspeaker-based setup and wearable hearing aids. We fitted a group of 15 OHI listeners with bilateral behind-the-ear devices that were programmed to have three different directional processing settings. Apart from source movement detectability, we assessed two other aspects of spatial awareness perception. Using a street scene with up to five environmental sound sources, the participants had to count the number of presented sources or to indicate the movement direction of a single target signal. The data analyses showed a clear influence of the number of concurrent sound sources and the starting position of the moving target signal on the participants’ performance, but no influence of the different hearing aid settings. Complementary artificial head recordings showed that the acoustic differences between the three hearing aid settings were rather small. Another explanation for the lack of effects of the tested hearing aid settings could be that the simulated street scenario was not sufficiently sensitive. Possible ways of improving the sensitivity of the laboratory measures while maintaining high ecological validity and complexity are discussed.

Auditory Acclimatization to Bilateral Hearing Aids: Effects on Sentence-in-Noise Processing Times and Speech-Evoked Potentials.

Using a longitudinal design, the present study sought to substantiate indications from two previous cross-sectional studies that hearing aid (HA) experience leads to improved speech processing abilities as quantified using eye-gaze measurements. Another aim was to explore potential concomitant changes in event-related potentials (ERPs) to speech stimuli. Groups of elderly novice (novHA) and experienced (expHA) HA users matched in terms of age and working memory capacity participated. The novHA users were acclimatized to bilateral HA fittings for up to 24 weeks. The expHA users continued to use their own HAs during the same period. The participants' speech processing abilities were assessed after 0 weeks (novHA: N = 16; expHA: N = 14), 12 weeks (novHA: N = 16; expHA: N = 14), and 24 weeks (N = 10 each). To that end, an eye-tracking paradigm was used for estimating how quickly the participants could grasp the meaning of sentences presented against background noise together with two similar pictures that either correctly or incorrectly depicted the meaning conveyed by the sentences (the "processing time"). Additionally, ERPs were measured with an active oddball paradigm requiring the participants to categorize word stimuli as living (targets) or nonliving (nontargets) entities. For all measurements, the stimuli were spectrally shaped according to individual real-ear insertion gains and presented via earphones. Concerning the processing times, no changes across time were found for the expHA group. After 0 weeks of HA use, the novHA group had significantly longer (poorer) processing times than the expHA group, consistent with previous findings. After 24 weeks, a significant mean improvement of ~30% was observed for the novHA users, leading to a performance comparable with that of the expHA group. Concerning the ERPs, no changes across time were found. The results from this exploratory study are consistent with the view that auditory acclimatization to HAs positively impacts speech comprehension in noise. Further research is needed to substantiate them.

Exploring the Effects of the Narrative Embodied in the Hearing Aid Fitting Process on Treatment Outcomes.

There is strong evidence from other fields of health, and growing evidence in audiology, that characteristics of the process of intervention as perceived by the client (embodied narratives) can have significant effects on treatment outcomes, independent of the technical properties of the intervention itself. This phenomenon deserves examination because studies of technical interventions that fail to take account of it may reach erroneous conclusions and because clinical practice can put such effects to therapeutic use. The aim of this study was to test the idea that embodied narratives might affect outcomes in hearing aid fitting. This was achieved by carrying out experiments in which technical (acoustic) differences between alternative hearing aid fittings were absent, while providing test subjects with a strong contrast between the processes apparently applied to derive the fittings being compared. Thus, any effects of contrasting narratives could be observed, free of acoustical confounds. The hypothesis was that narrative effects would be observed. A balanced crossover design was used, in which subjects received and evaluated two bilateral hearing aid fittings in succession. Subjects were deceived as to the true identical content of the hearing aid fittings being compared, but encouraged to believe that one fitting process was "interactive" and the other was "diagnostic" in character. Two almost identical experiments were undertaken: one with 24 experienced adult hearing aid users and another with 16 adult first-time users. Each hearing aid fitting was worn at home for 2 weeks, after which self-report outcome measures (Hearing Aid Performance Questionnaire, Hearing Handicap Inventory for the Elderly, and International Outcome Inventory for Hearing Aids) were administered. After the second test period, a short preference questionnaire was also completed. Twenty of the 24 experienced users showed a clear preference for one or the other fitting, and their self-report scores reflected these preferences. Effect sizes were comparable with those typically observed for true acoustical contrasts. No order effect was seen in this group. In contrast, 13 of the 16 first-time users preferred the second fitting. Trends in the self-report measures were similar for this group but weaker than for the experienced users. In both groups, the reasons given for subjects' preference were predominantly related to sound, despite there being no acoustical differences. This study suggests that the narrative embodied in a given fitting process can have a substantial effect on the perceived benefit of the treatment, independent of any acoustical differences, at least for experienced users. For first-time users, acclimatization seems to overshadow the purely narrative effect of any fitting process. In the future, research study designs should include steps to avoid narrative effects when technical parameters of hearing aids are the intended object of study. In clinical practice, the narrative is part of the therapeutic context, and one may design it for maximum beneficial effect.

Auditory acclimatization and hearing aids: late auditory evoked potentials and speech recognition following unilateral and bilateral amplification.

The aim of this study was to investigate changes in central auditory processing following unilateral and bilateral hearing aid fitting using a combination of physiological and behavioral measures: late auditory event-related potentials (ERPs) and speech recognition in noise, respectively. The hypothesis was that for fitted ears, the ERP amplitude would increase over time following hearing aid fitting in parallel with improvement in aided speech recognition. The N1 and P2 ERPs were recorded to 500 and 3000 Hz tones presented at 65, 75, and 85 dB sound pressure level to either the left or right ear. New unilateral and new bilateral hearing aid users were tested at the time of first fitting and after 12 weeks hearing aid use. A control group of long-term hearing aid users was tested over the same time frame. No significant changes in the ERP were observed for any group. There was a statistically significant 2% improvement in aided speech recognition over time for all groups, although this was consistent with a general test-retest effect. This study does not support the existence of an acclimatization effect observable in late ERPs following 12 weeks' hearing aid use.

Evaluation of Speech Intelligibility and Sound Localization Abilities with Hearing Aids Using Binaural Wireless Technology.

Wireless synchronization of the digital signal processing (DSP) features between two hearing aids in a bilateral hearing aid fitting is a fairly new technology. This technology is expected to preserve the differences in time and intensity between the two ears by co-ordinating the bilateral DSP features such as multichannel compression, noise reduction, and adaptive directionality. The purpose of this study was to evaluate the benefits of wireless communication as implemented in two commercially available hearing aids. More specifically, this study measured speech intelligibility and sound localization abilities of normal hearing and hearing impaired listeners using bilateral hearing aids with wireless synchronization of multichannel Wide Dynamic Range Compression (WDRC). Twenty subjects participated; 8 had normal hearing and 12 had bilaterally symmetrical sensorineural hearing loss. Each individual completed the Hearing in Noise Test (HINT) and a sound localization test with two types of stimuli. No specific benefit from wireless WDRC synchronization was observed for the HINT; however, hearing impaired listeners had better localization with the wireless synchronization. Binaural wireless technology in hearing aids may improve localization abilities although the possible effect appears to be small at the initial fitting. With adaptation, the hearing aids with synchronized signal processing may lead to an improvement in localization and speech intelligibility. Further research is required to demonstrate the effect of adaptation to the hearing aids with synchronized signal processing on different aspects of auditory performance.

Effects of independent bilateral compressive amplification on lateralization of a single source.

Use of compressive amplification in bilateral hearing aid fittings can disrupt binaural cues important to spatial hearing. The head‐related transfer function introduces direction‐dependent interaural time and level differences (ITDs and ILDs) which are consistent with one another. Independent bilateral compression, however, reduces ILDs such that they suggest a different, conflicting direction than ITDs. The reduction in ILDs is a dynamic effect that depends on the characteristics of the compression and the sound. Single‐channel compression was applied over a wide, high‐frequency band. Two conditions were run, with the high‐frequency channel presented to listeners in isolation or recombined with an unprocessed low‐frequency channel. Stimuli included pink noise bursts with varied onset slopes and rates of amplitude modulation and speech. The effects of compression on the perceived auditory objects were assessed using a semantic differential method, in which listeners rated various spatial attributes on sca...

Self-reported disability and handicap after hearing-aid fitting and benefit of hearing aids: comparison of fitting procedures, degree of hearing loss, experience with hearing aids and uni- and bilateral fittings

Self-reported outcome on hearing disability and handicap as well as overall health-related quality of life were measured after hearing-aid fitting in a large-scale clinical population. Fitting was performed according to two different procedures in a double-blind study design. We used a comparative procedure based on optimizing speech intelligibility scores and a strictly implemented fitting formula. Hearing disability and handicap were assessed with the hearing handicap and disability inventory and benefit of hearing aids with the abbreviated profile of hearing aid benefit. Effects on health-related quality of life and depression were assessed with the EuroQol-5D questionnaire and the geriatric depression scale. We found that hearing-aid fitting according to either procedure had a significantly positive effect on disability and handicap associated with hearing loss. This effect lasted for several months. Only the effect on disability persisted after 1-year of follow-up. Self-reported benefit from hearing aids was comparable for both fitting procedures. Unaided hearing disability was more pronounced in groups of participants with greater hearing loss, while the benefit of hearing aids was independent from the degree of hearing impairment. First-time hearing aid users reported greater benefit from their hearing aids. The added value from a bilateral hearing-aid fitting was not significant. Overall health-related quality of life and incidence of depression did not alter after hearing-aid fitting.

Hearing aids plus cochlear implants: Optimizing the bimodal pediatric fitting

Hearing aids plus cochlear implants: Optimizing the bimodal pediatric fitting

Candidacy for Bilateral Hearing Aids: A Retrospective Multicenter Study

The goal of this study was to find factors for refining candidacy criteria for bilateral hearing aid fittings. Clinical files of 1,000 consecutive hearing aid fittings were analyzed. Case history, audiometric, and rehabilitation data were collected from clinical files, and an extensive questionnaire on long-term outcome measures was conducted. After at least 2 years of hearing aid use, 505 questionnaires were returned. In order to compare differences in benefits between unilateral and bilateral fittings, two subgroups were composed in which most relevant variables (age, degree of hearing loss, and audiometric asymmetry) were matched for unilateral fittings (n=212) and bilateral fittings (n=477). The bilateral group had significantly higher benefit scores than the unilateral group for detection, speech intelligibility in reverberation, and localization, but poorer scores for comfort of loud sounds. The benefit of bilateral hearing aids was not significantly related to the level of technology of the hearing aids. The analysis of the relation between objective parameters and the subjective outcome measures showed that candidacy for a successful bilateral fitting could not be predicted from age, maximum speech intelligibility, employment, exposure to background noise, or social activities.

Education qualification levels and school careers of unilateral versus bilateral hearing aid users

Analyse the difference in school careers and secondary school qualification levels between unilateral hearing aid users and bilateral hearing aid users. Retrospective questionnaire study. Postal-based questionnaire. Names of adults known to have been fitted with unilateral or bilateral hearing aids during childhood were retrieved. This resulted in 292 names. Participants were selected using the following criteria: availability of the medical record, presence of bilateral hearing loss, completed secondary school education, normal IQ and a minimum aided word-recognition score of 70% at 10 years of age. The questionnaire was sent to 50 potential participants of whom 40 responded, resulting in two groups comprising 19 unilateral and 21 bilateral hearing aid users. A questionnaire was developed to obtain data on secondary school levels and aspects of the school careers, such as type of schools attended (mainstream versus special), repeating a school year and additional assistance (speech and language therapy, personal frequency modulation systems). Comparison of the benefit of bilateral hearing aid fitting versus unilateral hearing aid fitting on secondary school qualification level, type of school the children attended, class failure and additional assistance used. The group of bilaterally fitted hearing aid users eventually completed secondary school at a superior level than the unilaterally fitted users. 33% of binaural hearing aid users achieved qualifications giving access to a bachelors degree compared with 21% of unilateral users. There were no differences between those fitted with unilateral and bilateral hearing aids in the type of schools attended, repeating a school year and additional assistance. The bilateral hearing aid users obtained superior secondary school qualifications than the unilateral users but their school careers were comparable.

Benefits of Fitting One Versus Two Hearing Aids

Benefits of Fitting One Versus Two Hearing Aids

A survey of public health policy on bilateral fittings and comparison with market trends: The evidence-base required to frame policy

This report presents a review of the situation in a number of countries with respect to public health policy for funding of hearing aid services in general and support to bilateral fittings in particular. The data show considerable variations among the countries studied in number of hearing aids fitted per 1000 inhabitants, differing by a factor of 6 between the extremes. Also the percentage of bilateral fittings differs with an average estimated to be of the order of 50%. For hearing-impaired children, bilateral fittings are given full financial support in most countries studied. The data presented indicate the need for a reliable, scientifically valid evidence-base regarding bilateral hearing aid fitting.

Effects of bilateral versus unilateral hearing aid fitting on abilities measured by the Speech, Spatial, and Qualities of Hearing scale (SSQ)

The Speech, Spatial and Qualities of Hearing Scale (Gatehouse & Noble, ) was applied to three independent clinical groups: 144 people prior to being fitted with amplification; 118 people with six months experience with unilateral amplification; and 42 people with six months experience with bilateral amplification. For traditional speech hearing contexts (one-on-one, in groups, in quiet, in noise) there was benefit with one aid, and no further benefit with two. By contrast, hearing speech in demanding contexts (divided or rapidly switching attention) showed benefit with one aid and further benefit with two. In the spatial domain, directional hearing showed some benefit with one hearing aid, and particular further benefit in distance and movement discrimination from fitting with two. There was some benefit from unilateral fitting for elements of the qualities domains (clarity, naturalness, recognisability, segregation of sounds), with no consistent sign of further benefit from two. Bilateral fitting added benefit with respect to listening effort. Two hearing aids offer advantage in demanding and dynamic contexts; these contexts are argued as significant in the maintenance of social competence and emotional wellbeing. The present results go toward establishing the real-world advantages of bilateral hearing aid fitting and suggest that previous, inconclusive clinical findings reflect inquiry limited to more traditional areas of hearing function.SumarioSe aplicó la escala de cualidades auditiva, espacial y del lenguaje (Gatehouse & Noble, ) a tres grupos clínicos independientes: 144 personas, antes de adaptarles auxiliares auditivos; 118 personas con 6 meses de experiencia con amplificación unilateral y 42 personas con 6 meses de experiencia con amplificación bilateral. Se encontró beneficio de la amplificación unilateral en el contexto de habla tradicional (uno a uno, en grupo, en silencio y en ruido) y no hubo beneficio posterior en el modo bilateral. En contraste, bajo condiciones de discriminación del lenguaje en contexto demandante (atención dividida o cambio de rápido de atención) hubo beneficio con un solo un auxiliar, y mayor beneficio con dos. En el dominio espacial, hubo cierto beneficio en la audición direccional con un solo auxiliar auditivo y particularmente resultó benéfica la condición bilateral en la discriminación de distancia y movimiento. Hubo cierto beneficio de la condición unilateral para elementos de cualidad (claridad, naturalidad, fácil discriminación, segregación de sonidos) sin signos consistentes de beneficio con amplificación bilateral. La amplificación bilateral benefició el menor esfuerzo para escuchar. Hay ventajas con dos auxiliares auditivos en contexto demandante o dinámico; estos contextos son considerados como significativos en el mantenimiento de la competencia social y el bienestar emocional. Estos resultados se encaminan a establecer las ventajas de la amplificación bilateral en el mundo real y sugieren que los hallazgos clínicos previos e inconclusos, reflejan información limitada a áreas más tradicionales de la función auditiva.

Fitting strategies and candidature criteria for unilateral and bilateral hearing aid fittings

In this paper, hearing aid fitting strategies are reviewed and candidature criteria for unilateral and bilateral fittings are discussed. Fitting strategies are primarily governed by the objectives of hearing aid fitting that can be set in different ways. Based on common goals, fitting strategies can be broken down into three stages: (1) basic fitting, (2) fine-tuning and (3) verification and validation. A fine-tuning concept basing on so-called meta-controllers is described and the issue of bilateral fitting strategies is discussed. In a first order approach, bilateral hearing aids can be fitted in parallel as unilateral aids, followed by bilateral fine-tuning, making sure that loudness is balanced and overall loudness is accepted. Parallel fitting of bilateral aids is more favourable than sequential fitting to avoid rejection because of a negative experience with unilateral amplification due to difficulties in disadvantageous listening situations. Candidature criteria are presented by means of a flow chart structuring the decision making process and arriving at the conclusion that bilateral fitting should be considered the normal case. If there is any doubt about the benefit of bilateral fitting, a trial with bilateral aids should be performed.

Bilateral amplification and sound localization: Then and now

This article is concerned with the evolution and pros and cons of bilateral amplification. Determining whether a bilateral hearing aid fitting is superior to that of a monaural hearing aid is a long-standing question; for this reason, the trend toward bilateral amplification has been slow. However, it is now assumed that bilateral amplification has significant advantages over monaural amplification in most cases, a view that is supported by our localization results. In this article, we will address the advantages of bilateral hearing aids and reveal some new localization data that show that most listeners with bilateral amplification, when tested unaided, as well as normal-hearing listeners manifested very high degrees of symmetry in their judgments of perceived angle while listeners who routinely use monaural amplification and those with asymmetric hearing loss had relatively large asymmetries. These data show that asymmetry in localization judgments is a much more sensitive indicator of abnormal localization ability than the magnitude of localization errors.

Effects of Release Time and Directionality on Unilateral and Bilateral Hearing Aid Fittings in Complex Sound Fields

In studies to date, the effectiveness of the directional microphone has been investigated independently of the signal processing scheme used in the hearing aid. In addition, the number and placement of the background noise speakers can create an advantage for a particular polar pattern (i.e., cardioid, supercardioid, and hypercardioid) in any laboratory design. With these considerations in mind, the purpose of this investigation was twofold: (1) to determine the effect of different amplitude-compression release times on speech perception ability in noise, measured with directional microphone hearing aids, and (2) to determine the impact of environment (classroom vs anechoic chamber) on those measures. Ten subjects with mild to moderate sensorineural hearing loss participated. Using an eight-speaker complex sound field, speech perception was assessed in an anechoic chamber and a typical classroom environment. None of the release times resulted in superior performance in either the anechoic or classroom environment.

Effect of Spectral Shaping and Content on Loudness Discomfort

The purpose of this investigation was to study the impact of spectral shape and content on thresholds of discomfort (TD) for listeners with normal hearing and listeners with hearing loss. Secondary to that purpose was to quantify binaural summation at high intensities across complex stimulus conditions for both groups of listeners. Forty subjects (20 with normal hearing, 20 with hearing loss) participated. Complex acoustic stimuli (multitone and continuous discourse) were filtered to have four spectral shapes: (1) flat spectrum, (2) long-term average speech spectrum, (3) reverse long-term average speech spectrum, and (4) the TD contour derived for each subject from pure-tone TD obtained with eight pure tones from 250 to 4000 Hz. The results suggest that (1) TD for complex stimuli are lower for subjects with hearing loss compared with those with normal hearing, suggesting increased loudness summation with this population; (2) binaural summation of approximately 6 dB (independent of stimulus type, filter shape, or spectral content), indicating that a correction of similar magnitude for bilateral hearing aid fittings is appropriate; and (3) TD obtained at 750, 1500, and 3000 Hz accounted for approximately 60 percent of the variance in the complex TD measures, suggesting that TD at these frequencies be used to set the output obtained from a hearing aid with a 90-dB pure-tone sweep as the input stimulus.

Localization and speech-identification ability of hearing-impaired listeners using phase-preserving amplification

Hearing-impaired listeners experience increased difficulties recognizing speech and localizing sounds in adverse environments. This study investigated the benefits of signal processing in binaural hearing aids designed to preserve cues that accompany spatial location. The ability of listeners to localize click-trains in noise was tested, along with their ability both to localize and to identify words in noise (a dual task). Listeners experienced two types of bilateral hearing aid fittings: (1) a custom fitting that provided appropriate gain while also matching the phase measured near the tympanic membranes without the hearing aids, and (2) a conventional fitting (using the same hearing aid device) that provided the same gain with noncustom, linear phase. Testing occurred for each fitting immediately and following 3-months listening experience using a within-listener, within-device, randomized, single blind, crossover design. A rating-scale questionnaire was administered to assess perceived speech- hearing and spatial abilities. In the dual task, the listeners exhibited superior localization ability for the phase-preserving fitting initially and after 3-months experience. This advantage did not occur for the click-train localization task. Listeners rated their spatial abilities higher with the phase-preserving fitting, although little improvement was observed or reported for speech hearing.