Showing papers in "Trends in Amplification in 2008"

Selective attention in normal and impaired hearing.

Abstract: A common complaint among listeners with hearing loss (HL) is that they have difficulty communicating in common social settings. This article reviews how normal-hearing listeners cope in such settings, especially how they focus attention on a source of interest. Results of experiments with normal-hearing listeners suggest that the ability to selectively attend depends on the ability to analyze the acoustic scene and to form perceptual auditory objects properly. Unfortunately, sound features important for auditory object formation may not be robustly encoded in the auditory periphery of HL listeners. In turn, impaired auditory object formation may interfere with the ability to filter out competing sound sources. Peripheral degradations are also likely to reduce the salience of higher-order auditory cues such as location, pitch, and timbre, which enable normal-hearing listeners to select a desired sound source out of a sound mixture. Degraded peripheral processing is also likely to increase the time required to form auditory objects and focus selective attention so that listeners with HL lose the ability to switch attention rapidly (a skill that is particularly important when trying to participate in a lively conversation). Finally, peripheral deficits may interfere with strategies that normal-hearing listeners employ in complex acoustic settings, including the use of memory to fill in bits of the conversation that are missed. Thus, peripheral hearing deficits are likely to cause a number of interrelated problems that challenge the ability of HL listeners to communicate in social settings requiring selective attention.

Pitch perception and auditory stream segregation: implications for hearing loss and cochlear implants.

Abstract: Pitch is important for speech and music perception, and may also play a crucial role in our ability to segregate sounds that arrive from different sources. This article reviews some basic aspects of pitch coding in the normal auditory system and explores the implications for pitch perception in people with hearing impairments and cochlear implants. Data from normal-hearing listeners suggest that the low-frequency, low-numbered harmonics within complex tones are of prime importance in pitch perception and in the perceptual segregation of competing sounds. The poorer frequency selectivity experienced by many hearing-impaired listeners leads to less access to individual harmonics, and the coding schemes currently employed in cochlear implants provide little or no representation of individual harmonics. These deficits in the coding of harmonic sounds may underlie some of the difficulties experienced by people with hearing loss and cochlear implants, and may point to future areas where sound representation in auditory prostheses could be improved.

Time-frequency masking for speech separation and its potential for hearing aid design.

Abstract: A new approach to the separation of speech from speech-in-noise mixtures is the use of time-frequency (T-F) masking Originated in the field of computational auditory scene analysis, T-F masking performs separation in the time-frequency domain This article introduces the T-F masking concept and reviews T-F masking algorithms that separate target speech from either monaural or binaural mixtures, as well as microphone-array recordings The review emphasizes techniques that are promising for hearing aid design This article also surveys recent studies that evaluate the perceptual effects of T-F masking techniques, particularly their effectiveness in improving human speech recognition in noise An assessment is made of the potential benefits of T-F masking methods for the hearing impaired in light of the processing constraints of hearing aids Finally, several issues pertinent to T-F masking are discussed

Unilateral and mild bilateral hearing loss in children: past and current perspectives.

Abstract: Since the early 1980s, audiologists have become increasingly aware of the potential effect of even mild degrees of hearing loss on the psychoeducational and psychosocial outcomes of children. This review describes some of the key research findings during the past several decades that have led us to our current thinking about unilateral and mild bilateral hearing loss in children. The first section addresses unilateral hearing loss. This is followed by a review of the literature on mild bilateral hearing loss. Specifically, the issues addressed include the significance of permanent mild degrees of hearing loss on children's psychoeducational and psychosocial development and the speech, language, and auditory characteristics of children with mild degrees of hearing loss. Finally, some recommendations regarding the direction of future research are offered. This review is followed by 2 articles summarizing the proceedings of a 2005 workshop convened by the Centers for Disease Control and Prevention (CDC), Early Hearing Detection and Intervention (EHDI) program, and the Marion Downs Hearing Center to address concerns about the underidentification of-- and professionals' apparent lack of awareness of-- permanent unilateral and minimal to mild hearing loss in children.

Amplification considerations for children with minimal or mild bilateral hearing loss and unilateral hearing loss.

Abstract: Children with minimal or mild bilateral hearing loss and unilateral hearing loss are at higher risk for academic, speech-language, and social-emotional difficulties than their normal hearing peers. The choice to fit infants with moderate or greater degrees of bilateral hearing loss has been standard practice for most clinicians, but for those with minimal or mild bilateral hearing loss or unilateral hearing loss, the fitting of hearing technology must be based on limited data. Evidence does not yet exist to support all the management decisions that an audiologist must make upon identifying an infant with minimal or mild bilateral hearing loss or unilateral hearing loss. It is not yet known which children are at the greatest risk for educational problems nor is it known if the provision of early amplification in this population will help a child avoid later difficulties. Some of these considerations and current hearing technology options for children with minimal or mild bilateral hearing loss or unilateral hearing loss are reviewed in this article.

The choice of compression speed in hearing AIDS: theoretical and practical considerations and the role of individual differences.

Abstract: Compression is used in hearing aids to compensate for the effects of loudness recruitment. This article describes the distinction between, and relative merits of, slow and fast compression systems. A study of Gatehouse and coworkers leads to the following conclusions: (a) The benefit from compression is greatest among individuals who experience a wide range of sound levels within short periods of time, (b) slow compression generally leads to higher listening comfort than fast compression, (c) the benefit from fast compression varies across individuals, and those with high cognitive ability are able to benefit from fast compression to take advantage of temporal dips in a background sound. It is argued that listening in the dips depends on the ability to process the temporal fine structure of sounds. It is proposed that a test of the ability to process temporal fine structure might be useful for selecting compression speed for an individual.

Using Therapeutic Sound With Progressive Audiologic Tinnitus Management

Abstract: Management of tinnitus generally involves educational counseling, stress reduction, and/or the use of therapeutic sound. This article focuses on therapeutic sound, which can involve three objectives: (a) producing a sense of relief from tinnitus-associated stress (using soothing sound); (b) passively diverting attention away from tinnitus by reducing contrast between tinnitus and the acoustic environment (using background sound); and (c) actively diverting attention away from tinnitus (using interesting sound). Each of these goals can be accomplished using three different types of sound-broadly categorized as environmental sound, music, and speech-resulting in nine combinations of uses of sound and types of sound to manage tinnitus. The authors explain the uses and types of sound, how they can be combined, and how the different combinations are used with Progressive Audiologic Tinnitus Management. They also describe how sound is used with other sound-based methods of tinnitus management (Tinnitus Masking, Tinnitus Retraining Therapy, and Neuromonics).

Tinnitus outcomes assessment.

Abstract: Over the past two decades, recognition has grown that measures for evaluating treatment outcomes must be designed specifically to have high responsiveness. With that in mind, four major types of tinnitus measures are reviewed, including psychoacoustic measures, self-report questionnaires concerning functional effects of tinnitus, various rating scales, and global outcome measures. Nine commonly used tinnitus questionnaires, developed in the period 1980-2000, are reviewed. Because of many similarities between tinnitus and pain, comparisons between pain and tinnitus measures are discussed, and recommendations that have been made for developing a core set of measures to evaluate treatment-related changes in pain are presented as providing a fruitful path for developing a core set of measures for tinnitus. Finally, the importance of having both immediately obtainable outcome measures (psychoacoustic, rating scales, or single global measures) and longer term measures (questionnaires covering the negative effects of tinnitus) is emphasized for further work in tinnitus outcomes assessment.

The Role of Audiologic Evaluation in Progressive Audiologic Tinnitus Management

Abstract: Progressive Audiologic Tinnitus Management (PATM) is based on the premise that tinnitus is managed most efficiently using a hierarchy of clinical services that address different levels of need. PATM includes five levels of management: (a) triage; (b) audiologic evaluation; (c) group education; (d) tinnitus evaluation; and (e) individualized management. This article provides an overview of PATM and focuses on the procedures that make up the Level 2 Audiologic Evaluation. The evaluation is conducted to assess the potential need for medical, audiologic (hearing loss, tinnitus, hyperacusis), and/or mental health services. The Tinnitus Handicap Inventory, Hearing Handicap Inventory, and Tinnitus and Hearing Survey are used to differentiate effects of tinnitus and hearing loss. If indicated, patients are interviewed with the Tinnitus-Impact Screening Interview. Patients requiring amplification receive hearing aids. Often, management of hearing loss at Level 2 addresses any problems that were attributed to the tinnitus, which obviates further tinnitus-specific intervention.

Evaluating the benefit of hearing aids in solving the cocktail party problem

Abstract: The benefit of wearing hearing aids in multitalker, reverberant listening environments was evaluated in a study of speech-on-speech masking with two groups of listeners with hearing loss (younger/older). Listeners selectively attended a known spatial location in two room conditions (low/high reverberation) and identified target speech in the presence of two competing talkers that were either colocated or symmetrically spatially separated from the target. The amount of spatial release from masking (SRM) with bilateral aids was similar to that when listening unaided at or near an equivalent sensation level and was negatively correlated with the amount of hearing loss. When using a single aid, SRM was reduced and was related to the level of the stimulus in the unaided ear. Increased reverberation also reduced SRM in all listening conditions. Results suggest a complex interaction between hearing loss, hearing aid use, reverberation, and performance in auditory selective attention tasks.

Hearing Screening and Diagnostic Evaluation of Children With Unilateral and Mild Bilateral Hearing Loss

Abstract: More than 90% of newborns in the United States are now being screened for hearing loss. A large fraction of cases of unilateral hearing loss and mild bilateral hearing loss are not currently identified through newborn hearing screening. This is of concern because a preponderance of research has demonstrated that unilateral hearing loss and mild bilateral hearing loss can lead to developmental delays and educational problems for some children. To help address this probable underidentification of unilateral hearing loss and mild bilateral hearing loss among infants and children, the Centers for Disease Control and Prevention Early Hearing Detection and Intervention program and the Marion Downs Hearing Center convened a workshop in Breckenridge, Colorado, in July 2005. During this workshop, several issues related to screening and diagnosing unilateral hearing loss and mild bilateral hearing loss were identified, as well as recommendations for future research in this area. Issues identified included the lack of standardized definitions for permanent unilateral hearing loss and mild bilateral hearing loss; the use of screening protocols that are primarily designed to identify bilateral and unilateral hearing losses of a moderate degree or greater (eg, above 40 dB); calibration of screening equipment; availability of facilities that can provide the full range of audiologic, diagnostic, and management services to this pediatric population; and an overall lack of awareness by many professionals and families about the potential effect of unilateral hearing loss and mild bilateral hearing loss. Suggestions for future research, such as identifying ways to improve the identification of cases of unilateral hearing loss and mild bilateral hearing loss, were also discussed.

Reorganization of the adult auditory system: perceptual and physiological evidence from monaural fitting of hearing aids.

Abstract: Changes in the sensory environment modify our sensory experience and may result in experience-related or learning-induced reorganization within the central nervous system. Hearing aids change the sensory environment by stimulating a deprived auditory system; therefore, they may be capable of inducing changes within the central auditory system. Examples of studies that have shown hearing aid induced perceptual and/or physiological changes in the adult human auditory system are discussed. Evidence in the perceptual domain is provided by studies that have investigated (a) speech perception, (b) intensity discrimination, and (c) loudness perception. Evidence in the physiological domain is provided by studies that have investigated acoustic reflex thresholds and event-related potentials. Despite the controversy in the literature concerning the rate, extent, and clinical significance of the acclimatization effect, there is irrefutable evidence that the deprived auditory system of some listeners can be modified with hearing aid experience.

Early intervention for children with unilateral and mild bilateral degrees of hearing loss.

Abstract: Some children with unilateral hearing loss or mild bilateral hearing loss are at risk for developmental delays, educational difficulties, and other adverse effects. However, these children face several challenges in receiving services that can prevent such problems. Many do not meet existing eligibility requirements for early intervention services in their state. Information disseminated to professionals and parents often does not convey the significance of unilateral and mild bilateral hearing loss. Some professionals indicate that there are insufficient guidelines defining appropriate intervention services for these children. Factors that influence developmental outcomes in this population are not well understood, making it difficult to determine which children can benefit from intervention services. Additional data are needed about how to minimize or prevent adverse outcomes in these children. This article presents suggestions for intervention and future research that were developed by participants of the 2005 National Workshop on Mild and Unilateral Hearing Loss.

Causation of Permanent Unilateral and Mild Bilateral Hearing Loss in Children

Abstract: Children with permanent unilateral or mild bilateral hearing loss have been a focus of concern by audiologists, educators, and physicians for at least 2 decades. These children are known to be at risk for psychoeducational difficulties. However, despite this concern, little has been learned about the causative factors of these hearing losses and how those factors might be contributing to child development. This review of known causes of permanent unilateral and mild bilateral hearing loss in children is meant to draw attention to the importance of the search for etiologic factors. That is, the identification of the hearing loss should not signal the end of the diagnostic process but, rather, the beginning of a search for causation. With the combined efforts of audiologists, otolaryngologists, pediatricians, geneticists, and other medical professionals, we may enhance our understanding of the primary causes of unilateral and mild bilateral hearing loss and, perhaps, create links between causative factors and psychosocial and psychoeducational outcomes.

Treatment of Tinnitus With a Customized, Dynamic Acoustic Neural Stimulus: Underlying Principles and Clinical Efficacy:

Abstract: Tinnitus has been challenging to treat with consistently positive results. The Neuromonics Tinnitus Treatment is a newly available approach to the treatment of clinically significant, problematic tinnitus (and reduced sound tolerance) that was developed with the intention of simultaneously addressing the auditory, attentional, and emotional processes underlying the condition. It uses a prescribed acoustic stimulus, customized for each patient's individual audiometric profile, which provides a broad frequency stimulus to address the effects of auditory deprivation, promotes relief and relaxation with the intention of reducing engagement of the limbic system/amygdala and autonomic nervous system, and applies the principles of systematic desensitization to address the attentional processes. This article describes the underlying principles behind this approach. It also summarizes evidence for clinical efficacy from controlled clinical studies and from a private practice clinical setting, where it has been shown to provide consistently positive outcomes for patients meeting suitability criteria.

Somatosensory Pulsatile Tinnitus Syndrome: Somatic Testing Identifies a Pulsatile Tinnitus Subtype That Implicates the Somatosensory System

Abstract: A new tinnitus syndrome is described: high-pitched, cardiac-synchronous tinnitus, whose pulsations are suppressed by strong contractions or compressions of the neck and jaw muscles (somatic testing). 14 cases, 6 non-lateralized and 8 unilateral, are reported. In the non-lateralized cases, onset was bilateral. In the one intermittent case, while her tinnitus was absent her pulsatile tinnitus could be induced by somatic testing. No etiology was found from physical examination, imaging, or ancillary testing. Because these cases of pulsatile tinnitus can be both induced and suppressed by activation of the somatosensory system of the head or upper lateral neck, we propose that this syndrome is occurring from (a) cardiac synchronous somatosensory activation of the central auditory pathway or (b) failure of the somatosensory-auditory central nervous system interactions to suppress cardiac somatosounds.

The effects of cueing temporal and spatial attention on word recognition in a complex listening task in hearing-impaired listeners.

Abstract: In a complex listening situation such as a multiperson conversation, the demands on an individual's attention are considerable: There will often be many sounds occurring simultaneously, with continual changes in source and direction. A laboratory analog of this was designed to measure the benefit that helping attention (by visual cueing) would have on word identification. These words were presented unpredictably but were sometimes cued with a temporal cue or a temporal-and-spatial cue. Two groups of hearing-impaired, older-adult listeners participated, 57 unaided and 19 aided. There was a small effect of cueing: The cues gave a 2% benefit in word identification. A variety of subsidiary measures were collected, including the Test of Everyday Attention and the Speech, Spatial, & Qualities of Hearing Questionnaire, but their links with the benefits of cueing were few. The results demonstrate the difficulty of cueing attention to improve word recognition in a complex listening situation.

Treatments for Tinnitus

Abstract: The various forms of treatment for tinnitus that have been tested in properly controlled trials can be classified as pharmacological, acoustic-physical, and psychological. In clinical trials, no pharmacological agent has been shown to have lasting effect on the presence or severity of tinnitus, although there are promising signs in an animal model. Acoustic devices do not seem to influence tinnitus, although appropriately fitted hearing aids may slightly reduce its prominence. Of physical treatments, cortical implantation may hold some promise of being effective for tinnitus suppression in selected cases. A psychological treatment that has emerged as consistently beneficial is cognitive-behavior therapy in terms of affecting overall well-being and reducing level of tinnitus annoyance.

A multicenter trial of an assess-and-fit hearing aid service using open canal fittings and comply ear tips.

Abstract: Large potential benefits have been suggested for an assess-and-fit approach to hearing health care, particularly using open canal fittings. However, the clinical effectiveness has not previously been evaluated, nor has the efficiency of this approach in a National Health Service setting. These two outcomes were measured in a variety of clinical settings in the United Kingdom. Twelve services in England and Wales participated, and 540 people with hearing problems, not previously referred for assessment, were included. Of these, 68% (n = 369) were suitable and had hearing aids fitted to NAL NL1 during the assess-and-fit visit using either open ear tips, or Comply ear tips. The Glasgow Hearing Aid Benefit Profile was used to compare patients fitted with open ear tips with a group of patients from the English Modernization of Hearing Aid Services evaluation, who used custom earmolds. This showed a significant improvement in outcome for those with open ear tips after allowing for age and hearing loss in the analysis. In particular, the benefits of using bilateral open ear tips were significantly larger than bilateral custom ear-molds. This assess-and-fit model showed a mean service efficiency gain of about 5% to 10%. The actual gain will depend on current practice, in particular on the separate appointments used, the numbers of patients failing to attend appointments, and the numbers not accepting a hearing aid solution for their problem. There are potentially further efficiency and quality gains to be made if patients are appropriately triaged before referral.

The Design of a Project to Assess Bilateral Versus Unilateral Hearing Aid Fitting

Abstract: Binaural hearing provides advantages over monaural in several ways, particularly in difficult listening situations. For a person with bilateral hearing loss, the bilateral fitting of hearing aids thus seems like a natural choice. However, surprisingly few studies have been reported in which the additional benefit of bilateral versus unilateral hearing aid use has been investigated based on real-life experiences. Therefore, a project has been designed to address this issue and to find tools to identify people for whom the drawbacks would outweigh the advantages of bilateral fitting. A project following this design is likely to provide reliable evidence concerning differences in benefit between unilateral and bilateral fitting of hearing aids by evaluating correlations between entrance data and outcome measures and final preferences.

Auditory reality and self-assessment of hearing.

Abstract: Analyses are made of three problem areas in the realm of hearing disorder and its management, all of which are cogently informed by self-assessment: (a) prosthetic technology and the auditory ecology, (b) dimensions of benefit from amplification, and (c) dimensions of disability. Technology and ecology addresses the matter of “fitness for purpose” of different prosthetic schemes, moderated by people's hearing and listening environments (ecologies) and by what they bring to the task of hearing and listening. Dimensions of benefit covers what is achievable with prevailing technology, and also what people are aware of and identify as their needs. Dimensions of disability examines what has been recently learned about the range of hearing functions that need attending to in management of impaired hearing. A closing section provides a portrait of “auditory reality,” whose characteristics may be better appreciated when analyzed in contrast to and comparison with “visual reality.”

From the editor: special issue on tinnitus management.

Abstract: This issue of Trends in Amplification is devoted to tinnitus management by the audiologist, with special emphasis on sound therapy. Although most of us have had an episode of tinnitus at one time or another, some 50 million Americans have persistent tinnitus and 10 to 12 million of these people seek treatment because of the severity of their symptoms. Bothersome tinnitus can interfere with an individual's ability to concentrate or to sleep and can cause emotional disturbances. Various therapeutic approaches for managing tinnitus include sound therapy, psychological therapy, medication, and combinations of these approaches. In the first article, Henry, Zaugg, Myers, and Schechter describe a systematic approach for determining the required level of clinical management of tinnitus as determined by the severity of symptoms. Materials used during the assessment process are described and some of these materials are included as appendices. In the second article, Henry, Zaugg, Myers, and Schechter review general approaches to sound therapy, compare and contrast several different methods of using sound for tinnitus management, and present their own philosophy for using sound in the management of tinnitus symptoms. Theirs is a client-directed approach, wherein the person with tinnitus is given a role in deciding how sound will be used in specific situations. In this program, sound therapy, the primary mode of treatment, is supplemented by stress reduction and psychological counseling when needed. The client is educated with regard to three strategies for using sound and three types of sounds that can be used. Educational materials and materials to be used for the client in determining the helpfulness of the sound are provided. In the third article, Hanley and Davis describe a program of treatment that requires the use of a proprietary device for delivering a customized acoustic stimulus. The device is used as part of a 6-month program that includes education and counseling. The authors describe the rationale for the development of the device and the specific stimulus used. The results from clinical trials carried out during the development and modification of this treatment plan are reviewed, and descriptions of appropriate candidates for this form of treatment are included. One of the important components in evaluating any approach to the treatment of tinnitus is the availability of valid, reliable, and sensitive outcome measures. In the fourth article, Meikle, Stewart, Griest, and Henry critically review the methods currently used for evaluating tinnitus treatment outcomes: psychoacoustic measures, self-report questionnaires, rating scales, and global outcome measures. The authors point out the need for a standardized set of outcome measures responsive to treatment-related change for use in further studies of treatment efficacy. Next, Noble reviews the various approaches to the treatment of tinnitus symptoms—pharmacological, acoustic, and psychological—and the evidence or lack of evidence supporting their effectiveness. He points out the need for more research to support each approach. To date, the strongest evidence favors the use of cognitive behavior therapy. Finally, Levine, Namm, and Melcher provide a description of a form of pulsatile tinnitus with no apparent acoustic source. Physical examinations of 13 patients with pulsatile tinnitus were reported where the tinnitus could be either suppressed or induced by activating the somatosensory system of the head or lateral neck. The article includes a fascinating description of the process used by these physicians to determine the cause of such pulsatile tinnitus, including the examination methods and findings in each case. Two mechanisms are proposed to explain this form of pulsatile tinnitus; both implicate somatosensory modulation of auditory perception. The compendium of articles in this issue should serve as an introduction to tinnitus management for those uninvolved in this area and a resource for those who already use sound therapy in their audiology practices. Furthermore, the articles identify potential areas of research in the areas of intervention techniques and methods of assessing outcomes.

Stuart Gatehouse: a brief life.

Abstract: Stuart Gatehouse was an internationally renowned auditory scientist whose work on basic research, government policy, and clinical practice has directly improved the quality of life of adult hearing aid users. He addressed issues of relevance to the lives of hearing-impaired adults, especially on the impact of a hearing loss on an individual, the management of hearing loss, and the measurement of the benefits offered by hearing aids. He also influenced practice and service delivery and made major contributions to the delivery of audiological services in the United Kingdom, including chairing a report that directly led to their modernization in Scotland. This article describes his life and career.

From the Editor: Special Issue on Auditory Scene Analysis

Abstract: The most common complaint of a person with hearing loss is difficulty in understanding speech in noisy environments. Although communicating in noisy environments can prove challenging to people with normal hearing, the brain uses acoustic cues from a complex sound mixture to separate the speech signal of interest from competing sounds, a process known as auditory scene analysis. In a cocktail party, we can thus identify and concentrate on the speech of the person with whom we are speaking from the competing speech of other talkers, or follow a conversation among multiple talkers when seated at a table in a noisy restaurant. Although it has long been known that people with hearing loss have greater difficulty decoding speech in noisy situations (with or without hearing aids), little was known about how hearing loss or how the signal processing in hearing prostheses (hearing aids or cochlear implants) might affect specific aspects of listening thought to be important to auditory scene analysis. This issue of Trends in Amplification contains a series of articles that focus on aspects of listening in complex environments by persons with hearing loss, the effect of hearing aids and cochlear implants on listener performance in difficult listening environments, and how information about the mechanisms underlying auditory scene analysis might be used to improve the design of hearing aids and cochlear implants. In the first article, Shinn-Cunningham and Best focus on the role of selective attention in complex listening situations, that is, the “cocktail party” problem. They provide a description and explanation of why and how listeners with normal hearing are able to use attention to separate the wanted signal from a mixture of multiple voices, and they explain how the degradation of “bottom-up” cues because of hearing loss might affect auditory object formation and the ability to use selective attention. Finally, the authors address how hearing aids might help or hinder listening in complex listening environments. In the second article, Marrone, Mason, and Kidd report the results of a study investigating the ability of hearing aid users to benefit from spatial separation of the target talker and competing talkers (spatial release from masking) in reverberant environments. Listeners with hearing loss were tested with and without their personal hearing aids (unilateral and bilateral test conditions). Age-matched listeners with normal hearing served as a control group. The study revealed that listeners with hearing loss did obtain benefit from spatial separation of the target and maskers, but the spatial release from masking was less than that obtained by listeners with normal hearing. Greater benefit was obtained in the bilateral listening condition. The third article, by Oxenham, focuses on the role of pitch in grouping sounds from the same source and segregating sounds from different sources when listening in complex environments. The article provides a tutorial on current models of pitch perception, as well as a review of research on pitch perception and pitch and sound source segregation by listeners with normal hearing and hearing loss. The importance of preserving spectral information and temporal fine structure in hearing aid and cochlear implant processors is emphasized. In the final article, Wang describes an engineering approach to the problem of separating signal from noise. Wang introduces the idea of using time-frequency masks for the purpose of separating speech from interfering noise and also reviews recent research in this area. The suitability of this approach for hearing aid applications is discussed.

Stuart Gatehouse: the international perspective.

Abstract: The international contributions of Stuart Gatehouse are reviewed in three areas: as a scientist, as an advisor to health policy makers, and as a participant in international conferences. He was able, as no other auditory scientist of his time, to bridge the gap between scientific and clinical research. His ability to apply sound scientific principles to issues of clinical importance was most apparent in his work in three main areas of his research: acclimatization to amplified speech, auditory disability and hearing aid benefit, and candidature for linear and nonlinear signal processing.

Stuart Gatehouse: a personal appreciation.

Abstract: Stuart Gatehouse worked in the MRC Institute of Hearing Research Scottish Section for 29 years until his untimely death in 2007. The former director records a personal appreciation but also an explanation, for those who did not know him well, of the mixture of qualities that made him an outstanding applied scientist.