On Detectable and Meaningful Speech-Intelligibility Benefits.

The most important parameter that affects the ability to hear and understand speech in the presence of background noise is the signal-to-noise ratio (SNR). Despite decades of research in speech intelligibility, it is not currently known how much improvement in SNR is needed to provide a meaningful benefit to someone. We propose that the underlying psychophysical basis to a meaningful benefit should be the just noticeable difference (JND) for SNR. The SNR JND was measured in a series of experiments using both adaptive and fixed-level procedures across participants of varying hearing ability. The results showed an average SNR JND of approximately 3 dB for sentences in same-spectrum noise. The role of the stimulus and link to intelligibility was examined by measuring speech-intelligibility psychometric functions and comparing the intelligibility JND estimated from those functions with measured SNR JNDs. Several experiments were then conducted to establish a just meaningful difference (JMD) for SNR. SNR changes that could induce intervention-seeking behaviour for an individual were measured with subjective scaling and report, using the same stimuli as the SNR JND experiment as pre- and post-benefit examples. The results across different rating and willingness-to-change tasks showed that the mean ratings increased near linearly with a change in SNR, but a change of at least 6 dB was necessary to reliably motivate participants to seek intervention. The magnitude of the JNDs and JMDs for speech-intelligibility benefits measured here suggest a gap between what is achievable and what is meaningful.

International Collegium of Rehabilitative Audiology (ICRA) recommendations for the construction of multilingual speech tests. ICRA Working Group on Multilingual Speech Tests.

OBJECTIVE: To provide guidelines for the development of two types of closed-set speech-perception tests that can be applied and interpreted in the same way across languages. The guidelines cover the digit triplet and the matrix sentence tests that are most commonly used to test speech recognition in noise. They were developed by a working group on Multilingual Speech Tests of the International Collegium of Rehabilitative Audiology (ICRA). DESIGN: The recommendations are based on reviews of existing evaluations of the digit triplet and matrix tests as well as on the research experience of members of the ICRA Working Group. They represent the results of a consensus process. RESULTS: The resulting recommendations deal with: Test design and word selection; Talker characteristics; Audio recording and stimulus preparation; Masking noise; Test administration; and Test validation. CONCLUSIONS: By following these guidelines for the development of any new test of this kind, clinicians and researchers working in any language will be able to perform tests whose results can be compared and combined in cross-language studies.

The effect of hearing aid microphone mode on performance in an auditory orienting task.

OBJECTIVES: Although directional microphones on a hearing aid provide a signal-to-noise ratio benefit in a noisy background, the amount of benefit is dependent on how close the signal of interest is to the front of the user. It is assumed that when the signal of interest is off-axis, users can reorient themselves to the signal to make use of the directional microphones to improve signal-to-noise ratio. The present study tested this assumption by measuring the head-orienting behavior of bilaterally fit hearing-impaired individuals with their microphones set to omnidirectional and directional modes. The authors hypothesized that listeners using directional microphones would have greater difficulty in rapidly and accurately orienting to off-axis signals than they would when using omnidirectional microphones. DESIGN: The authors instructed hearing-impaired individuals to turn and face a female talker in simultaneous surrounding male-talker babble. Participants pressed a button when they felt they were accurately oriented in the direction of the female talker. Participants completed three blocks of trials with their hearing aids in omnidirectional mode and three blocks in directional mode, with mode order randomized. Using a Vicon motion tracking system, the authors measured head position and computed fixation error, fixation latency, trajectory complexity, and proportion of misorientations. RESULTS: Results showed that for larger off-axis target angles, listeners using directional microphones took longer to reach their targets than they did when using omnidirectional microphones, although they were just as accurate. They also used more complex movements and frequently made initial turns in the wrong direction. For smaller off-axis target angles, this pattern was reversed, and listeners using directional microphones oriented more quickly and smoothly to the targets than when using omnidirectional microphones. CONCLUSIONS: The authors argue that an increase in movement complexity indicates a switch from a simple orienting movement to a search behavior. For the most off-axis target angles, listeners using directional microphones appear to not know which direction to turn, so they pick a direction at random and simply rotate their heads until the signal becomes more audible. The changes in fixation latency and head orientation trajectories suggest that the decrease in off-axis audibility is a primary concern in the use of directional microphones, and listeners could experience a loss of initial target speech while turning toward a new signal of interest. If hearing-aid users are to receive maximum directional benefit in noisy environments, both adaptive directionality in hearing aids and clinical advice on using directional microphones should take head movement and orientation behavior into account.

Amplification with hearing aids for patients with tinnitus and co-existing hearing loss.

BACKGROUND: Tinnitus is described as the perception of sound or noise in the absence of real acoustic stimulation. In the current absence of a cure for tinnitus, clinical management typically focuses on reducing the effects of co-morbid symptoms such as distress or hearing loss. Hearing loss is commonly co-morbid with tinnitus and so logic implies that amplification of external sounds by hearing aids will reduce perception of the tinnitus sound and the distress associated with it. OBJECTIVES: To assess the effects of hearing aids specifically in terms of tinnitus benefit in patients with tinnitus and co-existing hearing loss. SEARCH METHODS: We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the search was 19 August 2013. SELECTION CRITERIA: Randomised controlled trials and non-randomised controlled trials recruiting adults with subjective tinnitus and some degree of hearing loss, where the intervention involves amplification with hearing aids and this is compared to interventions involving other medical devices, other forms of standard or complementary therapy, or combinations of therapies, no intervention or placebo interventions. DATA COLLECTION AND ANALYSIS: Three authors independently screened all selected abstracts. Two authors independently extracted data and assessed those potentially suitable studies for risk of bias. For studies meeting the inclusion criteria, we used the mean difference (MD) to compare hearing aids with other interventions and controls. MAIN RESULTS: One randomised controlled trial (91 participants) was included in this review. We judged the trial to have a low risk of bias for method of randomisation and outcome reporting, and an unclear risk of bias for other criteria. No non-randomised controlled trials meeting our inclusion criteria were identified. The included study measured change in tinnitus severity (primary measure of interest) using a tinnitus questionnaire measure, and change in tinnitus loudness (secondary measure of interest) on a visual analogue scale. Other secondary outcome measures of interest, namely change in the psychoacoustic characteristics of tinnitus, change in self reported anxiety, depression and quality of life, and change in neurophysiological measures, were not investigated in this study. The included study compared hearing aid use to sound generator use. The estimated effect on change in tinnitus loudness or severity as measured by the Tinnitus Handicap Inventory score was compatible with benefits for both hearing aids or sound generators but no difference was found between the two alternative treatments (MD -0.90, 95% confidence interval (CI) -7.92 to 6.12) (100-point scale); moderate quality evidence. No negative or adverse events were reported. AUTHORS' CONCLUSIONS: The current evidence base for hearing aid prescription for tinnitus is limited. To be useful, future studies should make appropriate use of blinding and be consistent in their use of outcome measures. Whilst hearing aids are sometimes prescribed as part of tinnitus management, there is currently no evidence to support or refute their use as a more routine intervention for tinnitus.

A method for measuring the intelligibility of uninterrupted, continuous speech.

Speech-in-noise tests commonly use short, discrete sentences as representative samples of everyday speech. These tests cannot, however, fully represent the added demands of understanding ongoing, linguistically complex speech. Using a new monitoring method to measure the intelligibility of continuous speech and a standard trial-by-trial, speech-in-noise test the effects of target duration and linguistic complexity were examined. For a group of older hearing-impaired listeners, significantly higher speech reception thresholds were found for continuous, complex speech targets than for syntactically simple sentences. The results highlight the need to sample speech intelligibility in a variety of everyday speech-in-noise scenarios.

The perception of apparent auditory source width in hearing-impaired adults.

In a previous study [Whitmer, Seeber and Akeroyd, J. Acoust. Soc. Am. 132, 369-379 (2012)], it was demonstrated that older hearing-impaired (HI) listeners produced visual sketches of headphone-presented noises that were insensitive to changes in interaural coherence. The current study further explores this insensitivity by comparing (a) binaural temporal fine-structure (TFS) resolution and (b) sound localization precision to (c) auditory source width judgments. Thirty-five participants aged 26-81 years with normal to moderately impaired hearing (a) discriminated interaurally phase-shifted tones from diotic tones presented over headphones, (b) located 500-ms speech-spectrum filtered click trains presented over loudspeakers between ±30° in quiet, and (c) sketched the perceived width of low-pass, high-pass, and speech-spectrum noise stimuli presented over loudspeakers from 0° and simultaneously from ±45° at attenuations of 0-20 dB to generate partially coherent stimuli. The results showed a decreasing sensitivity to width with age and impairment which was related to binaural TFS threshold: the worse one's threshold-which was correlated with age-the less the perceived width increased with decreasing interaural coherence. These results suggest that senescent changes to the auditory system do not necessarily lead to perceptions of broader, more diffuse sound images based on interaural coherence.

Proposed norms for the Glasgow hearing-aid benefit profile (Ghabp) questionnaire.

OBJECTIVE: To form a normative set of responses to the GHABP questionnaire from a large regional dataset. DESIGN: Participants were asked to rate their hearing disability, handicap, hearing-aid (HA) use, HA benefit, HA satisfaction, and residual (aided) disability on a five-point scale for four situations: quiet conversation, television (TV) listening, noisy conversation, and group conversation. A subset of participants also estimated the time spent in these situations. STUDY SAMPLE: A group of 1574 adults with normal to profound hearing thresholds participated. RESULTS: There was a significant relationship between increasing perceived disability and increasing hearing loss as given by the better-ear audiometric average (BEA). Responses for HA measures did not vary greatly with hearing loss: HA use was reported as high, whereas residual disability, HA benefit, and satisfaction were all reported on average as moderate. CONCLUSIONS: The results can be used as a normative dataset with which to evaluate individual responses in the clinic, where the GHABP provides a useful short-form questionnaire to engage the patient. The lack of systematic changes in hearing-aid related responses shows room for improvement in the benefit afforded by amplification.

A factor analysis of the SSQ (Speech, Spatial, and Qualities of Hearing Scale).

OBJECTIVE: The speech, spatial, and qualities of hearing questionnaire (SSQ) is a self-report test of auditory disability. The 49 items ask how well a listener would do in many complex listening situations illustrative of real life. The scores on the items are often combined into the three main sections or into 10 pragmatic subscales. We report here a factor analysis of the SSQ that we conducted to further investigate its statistical properties and to determine its structure. DESIGN: Statistical factor analysis of questionnaire data, using parallel analysis to determine the number of factors to retain, oblique rotation of factors, and a bootstrap method to estimate the confidence intervals. STUDY SAMPLE: 1220 people who have attended MRC IHR over the last decade. RESULTS: We found three clear factors, essentially corresponding to the three main sections of the SSQ. They are termed "speech understanding", "spatial perception", and "clarity, separation, and identification". Thirty-five of the SSQ questions were included in the three factors. There was partial evidence for a fourth factor, "effort and concentration", representing two more questions. CONCLUSIONS: These results aid in the interpretation and application of the SSQ and indicate potential methods for generating average scores.

Muddy, muddled, or muffled? Understanding the perception of audio quality in music by hearing aid users.

Introduction: Previous work on audio quality evaluation has demonstrated a developing convergence of the key perceptual attributes underlying judgments of quality, such as timbral, spatial and technical attributes. However, across existing research there remains a limited understanding of the crucial perceptual attributes that inform audio quality evaluation for people with hearing loss, and those who use hearing aids. This is especially the case with music, given the unique problems it presents in contrast to human speech. Method: This paper presents a sensory evaluation study utilising descriptive analysis methods, in which a panel of hearing aid users collaborated, through consensus, to identify the most important perceptual attributes of music audio quality and developed a series of rating scales for future listening tests. Participants (N = 12), with a hearing loss ranging from mild to severe, first completed an online elicitation task, providing single-word terms to describe the audio quality of original and processed music samples; this was completed twice by each participant, once with hearing aids, and once without. Participants were then guided in discussing these raw terms across three focus groups, in which they reduced the term space, identified important perceptual groupings of terms, and developed perceptual attributes from these groups (including rating scales and definitions for each). Results: Findings show that there were seven key perceptual dimensions underlying music audio quality (clarity, harshness, distortion, spaciousness, treble strength, middle strength, and bass strength), alongside a music audio quality attribute and possible alternative frequency balance attributes. Discussion: We outline how these perceptual attributes align with extant literature, how attribute rating instruments might be used in future work, and the importance of better understanding the music listening difficulties of people with varied profiles of hearing loss.

Interventions for the prevention of postoperative ear discharge after insertion of ventilation tubes (grommets) in children.

BACKGROUND: Grommets are frequently inserted in children's ears for acute otitis media and otitis media with effusion. A common complication is postoperative ear discharge (otorrhoea). A wide range of treatments are used to prevent the discharge, but there is no consensus on whether or not intervention is necessary nor which is the most effective intervention. OBJECTIVES: To assess the effectiveness of prophylactic interventions, both topical and systemic, in reducing the incidence of otorrhoea following the surgical insertion of grommets in children. SEARCH METHODS: We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the search was 3 July 2012. SELECTION CRITERIA: We included randomised controlled trials (RCTs) that compared the efficacy of prophylactic interventions against placebo/control and/or with other prophylactic interventions for postoperative otorrhoea in children. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed study eligibility and risk of bias, and extracted data. The outcome data were dichotomous for all the included trials. We calculated individual and pooled risk ratios (RR) using the Mantel-Haenszel fixed-effect method. We also calculated the numbers needed to treat to benefit (NNTB). MAIN RESULTS: We found 15 eligible RCTs (2476 children, aged from four months to 17 years). We graded seven RCTs as being at a low risk of bias (n = 926 children) and for an eighth RCT we also graded two of the arms as being at a low risk of bias. We graded the other seven trials as being at a high risk of bias.For a single application at surgery, there was evidence from two low risk of bias trials that at two weeks postoperatively the risk of otorrhoea was reduced by multiple saline washouts (from 30% to 16%; RR 0.52, 95% confidence interval (CI) 0.27 to 1.00; NNTB 7; one RCT; 140 children) and antibiotic/steroid ear drops (from 9% to 1%; RR 0.13, 95% CI 0.03 to 0.57; NNTB 13; one RCT; 322 ears). A meta-analysis of two low risk of bias trials (222 ears) failed to find an effect of a single application of antibiotic/steroid ear drops at four to six weeks postoperatively.For a prolonged application of an intervention, there was evidence from four low risk of bias trials that the risk of otorrhoea was reduced two weeks postoperatively by antibiotic ear drops (from 15% to 8%; RR 0.54, 95% CI 0.30 to 0.97; NNTB 15; one RCT; 372 children), antibiotic/steroid ear drops (from 39% to 5%; RR 0.13, 95% CI 0.05 to 0.31; NNTB 3; one RCT; 200 children), aminoglycoside/steroid ear drops (from 15% to 5%; RR 0.37, 95% CI 0.18 to 0.74; NNTB 11; one RCT; 356 children) or oral antibacterial agents/steroids (from 39% to 5%; RR 0.13, 95% CI 0.03 to 0.51; NNTB 3; one RCT; 77 children).Only one trial assessed the secondary outcome of ototoxicity, but no effect was found. There were no trials that assessed quality of life. AUTHORS' CONCLUSIONS: Our review found that each of the following were effective at reducing the rate of otorrhoea up to two weeks following surgery: (1) multiple saline washouts at surgery, (2) a single application of topical antibiotic/steroid drops at surgery, (3) a prolonged application of topical drops (namely antibiotic ear drops, antibiotic/steroid eardrops or aminoglycoside/steroid ear drops) and (4) a prolonged application of oral antibacterial agents/steroids. However, the rate of otorrhoea between RCTs varied greatly and the higher the rates of otorrhoea within a RCT, the smaller the NNTB for therapy.We conclude that if a surgeon has a high rate of postoperative otorrhoea in children then either saline irrigation or antibiotic ear drops at the time of surgery would significantly reduce that rate. If topical drops are chosen, it is suggested that to reduce the cost and potential for ototoxic damage this be a single application at the time of surgery and not prolonged thereafter.

Measuring the apparent width of auditory sources in normal and impaired hearing.

It is often assumed that single sources of sound are perceived as being punctate, but this cannot be guaranteed, especially for hearing-impaired listeners. Any impairment that gives a reduction at the periphery in the accuracy of coding fine-scale temporal information must give a slight interaural jitter in the temporal information passed to higher centres, and so would be expected to lead to an effective reduction in the interaural coherence (IC) of any stimulus. This would lead to deficits in locating sounds, but deficits of imprecision, not inaccuracy. In turn, this implies that older hearing-impaired individuals should have a diminished perception of auditory space, affecting their abilities to perceive clear, concise, punctate spatial impressions or to separate sounds by location. The current work tested this hypothesis by using two separate visual-analogy methods to measure auditory source width for broadband sounds. In one method, the listener sketched the auditory image, a visual-description task, and for the other, the listener selected the closest one of a set of pre-drawn visual sketches (note that the first is an open-set experiment, whereas the second is a closed-set experiment). We found that older hearing-impaired listeners had increased difficulty in judging changes in interaural coherence, showing a corresponding insensitivity to auditory source width in the visual-analogy tasks.

The internal representation of vowel spectra investigated using behavioral response-triggered averaging.

Listeners presented with noise were asked to press a key whenever they heard the vowels [a] or [i:]. The noise had a random spectrum, with levels in 60 frequency bins changing every 0.5 s. Reverse correlation was used to average the spectrum of the noise prior to each key press, thus estimating the features of the vowels for which the participants were listening. The formant frequencies of these reverse-correlated vowels were similar to those of their respective whispered vowels. The success of this response-triggered technique suggests that it may prove useful for estimating other internal representations, including perceptual phenomena like tinnitus.

A short form of the Speech, Spatial and Qualities of Hearing scale suitable for clinical use: the SSQ12.

OBJECTIVE: To develop and evaluate a 12-item version of the Speech, Spatial and Qualities of Hearing scale for use in clinical research and rehabilitation settings, and provide a formula for converting scores between the full (SSQ49) and abbreviated (SSQ12) versions. DESIGN: Items were selected independently at the three centres (Eriksholm Research Centre, MRC Institute of Hearing Research, University of New England) to be representative of the complete scale. A consensus was achieved after discussion. STUDY SAMPLE: The data set (n = 1220) used for a factor analysis (Akeroyd et al, submitted) was re-analysed to compare original SSQ scores (SSQ49) with scores on the short version (SSQ12). RESULTS: A scatter-plot of SSQ12 scores against SSQ49 scores showed that SSQ12 score was about 0.6 of a scale point lower than the SSQ49 (0-10 scale) in the re-analysis of the Akeroyd et al data. SSQ12 scores lay on a slightly steeper slope than scores on the SSQ49. CONCLUSIONS: The SSQ12 provides similar results to SSQ49 in a large clinical research sample. The slightly lower average SSQ12 score and the slightly steeper slope reflect the composition of this short form relative to the SSQ49.

Inferring the basis of binaural detection with a modified autoencoder.

The binaural system utilizes interaural timing cues to improve the detection of auditory signals presented in noise. In humans, the binaural mechanisms underlying this phenomenon cannot be directly measured and hence remain contentious. As an alternative, we trained modified autoencoder networks to mimic human-like behavior in a binaural detection task. The autoencoder architecture emphasizes interpretability and, hence, we "opened it up" to see if it could infer latent mechanisms underlying binaural detection. We found that the optimal networks automatically developed artificial neurons with sensitivity to timing cues and with dynamics consistent with a cross-correlation mechanism. These computations were similar to neural dynamics reported in animal models. That these computations emerged to account for human hearing attests to their generality as a solution for binaural signal detection. This study examines the utility of explanatory-driven neural network models and how they may be used to infer mechanisms of audition.

The long-term impacts of hearing loss, tinnitus and poor balance on the quality of life of people living with and beyond cancer after platinum-based chemotherapy: a literature review.

PURPOSE: To elucidate the long-term impacts of hearing loss, tinnitus and balance in people living with and beyond cancer (LWBC) treated with platinum-based chemotherapy (PBCT). METHODS: A literature search was conducted between March and June 2022 using PubMed, Web of Science and Google Scholar. Full-text papers in English were included. Articles explored the impacts of hearing loss, tinnitus and balance and discussed them in the context of treatment. If PBCT was used in conjunction with other treatments, the article was included. There were no constraints on age, cancer type, publication date, location, study design or data type. Sixteen studies and two reviews were included. RESULTS: Hearing loss and tinnitus can cause communication difficulties and subsequent social withdrawal. There were deficits in cognition, child development and educational performance. Employment and the ease of everyday life were disrupted by hearing loss and tinnitus, whereas poor balance interfered with walking and increased the risk of falls. Depression and anxiety were related to ototoxicity. Most notable were the differing mindsets experienced by adults LWBC with ototoxicity. There was evidence of inadequate monitoring of ototoxicity by clinicians and a lack of communication between clinicians and patients about ototoxicity as a side effect. CONCLUSIONS: Ototoxicity has a negative long-term impact on multiple areas of life for adults and children LWBC. This can compromise their quality of life. IMPLICATIONS FOR CANCER SURVIVORS: Increased awareness, monitoring and education surrounding these issues may lead to earlier intervention and better management of ototoxicity, enhancing the quality of life of people LWBC.

The executive disruption model of tinnitus distress: Model validation in two independent datasets using factor score regression.

This study presents the executive disruption model (EDM) of tinnitus distress and subsequently validates it statistically using two independent datasets (the Construction Dataset: n = 96 and the Validation Dataset: n = 200). The conceptual EDM was first operationalised as a structural causal model (construction phase). Then multiple regression was used to examine the effect of executive functioning on tinnitus-related distress (validation phase), adjusting for the additional contributions of hearing threshold and psychological distress. For both datasets, executive functioning negatively predicted tinnitus distress score by a similar amount (the Construction Dataset: ß = -3.50, p = 0.13 and the Validation Dataset: ß = -3.71, p = 0.02). Theoretical implications and applications of the EDM are subsequently discussed; these include the predictive nature of executive functioning in the development of distressing tinnitus, and the clinical utility of the EDM.

The impact of tinnitus on adult cochlear implant recipients: A mixed-method approach.

BACKGROUND: Tinnitus is a common problem in patients with a cochlear implant (CI). Between 4% and 25% of CI recipients experience a moderate to severe tinnitus handicap. However, apart from handicap scores, little is known about the real-life impact tinnitus has on those with CIs. We aimed to explore the impact of tinnitus on adult CI recipients, situations impacting tinnitus, tinnitus-related difficulties and their management strategies, using an exploratory sequential mixed-method approach. METHODS: A 2-week web-based forum was conducted using Cochlear Ltd.'s online platform, Cochlear Conversation. A thematic analysis was conducted on the data from the forum discussion to develop key themes and sub-themes. To quantify themes and sub-themes identified, a survey was developed in English with face validity using cognitive interviews, then translated into French, German and Dutch and disseminated on the Cochlear Conversation platform, in six countries (Australia, France, Germany, New Zealand, the Netherlands and United Kingdom). Participants were adult CI recipients experiencing tinnitus who received a Cochlear Ltd. CI after 18 years of age. RESULTS: Four key themes were identified using thematic analysis of the discussion forum: tinnitus experience, situations impacting tinnitus, difficulties associated with tinnitus and tinnitus management. Among the 414 participants of the survey, tinnitus burden on average was a moderate problem without their sound processor and not a problem with the sound processor on. Fatigue, stress, concentration, group conversation and hearing difficulties were the most frequently reported difficulties and was reported to intensify when not wearing the sound processor. For most CI recipients, tinnitus seemed to increase when performing a hearing test, during a CI programming session, or when tired, stressed, or sick. To manage their tinnitus, participants reported turning on their sound processor and avoiding noisy environments. CONCLUSION: The qualitative analysis showed that tinnitus can affect everyday life of CI recipients in various ways and highlighted the heterogeneity in their tinnitus experiences. The survey findings extended this to show that tinnitus impact, related difficulties, and management strategies often depend on sound processor use. This exploratory sequential mixed-method study provided a better understanding of the potential benefits of sound processor use, and thus of intracochlear electrical stimulation, on the impact of tinnitus.

Apparent auditory source width insensitivity in older hearing-impaired individuals.

Previous studies have shown a loss in the precision of horizontal localization responses of older hearing-impaired (HI) individuals, along with potentially poorer neural representations of sound-source location. These deficits could be the result or corollary of greater difficulties in discriminating spatial images, and the insensitivity to punctate sound sources. This hypothesis was tested in three headphone-presentation experiments varying interaural coherence (IC), the cue most associated with apparent auditory source width. First, thresholds for differences in IC were measured for a broad sampling of participants. Older HI participants were significantly worse at discriminating IC across reference values than younger normal-hearing participants. These results are consistent with senescent increases in temporal jitter. Performance decreased with age, a finding corroborated in a second discrimination experiment using a separate group of participants matched for hearing loss. This group also completed a third, visual experiment, with both a cross-mapping task where they drew the size of the sound they heard and the identification task where they chose the image that best corresponded to what they heard. The results from the visual tasks indicate that older HI individuals do not hear punctate images and are relatively insensitive to changes in width based on IC.

Auditory externalization in hearing-impaired listeners: the effect of pinna cues and number of talkers.

Hearing-aid wearers have reported sound source locations as being perceptually internalized (i.e., inside their head). The contribution of hearing-aid design to internalization has, however, received little attention. This experiment compared the sensitivity of hearing-impaired (HI) and normal-hearing listeners to externalization cues when listening with their own ears and simulated behind-the-ear hearing-aids in increasingly complex listening situations and reduced pinna cues. Participants rated the degree of externalization using a multiple-stimulus listening test for mixes of internalized and externalized speech stimuli presented over headphones. The results showed that HI listeners had a contracted perception of externalization correlated with high-frequency hearing loss.