Maximizing Cochlear Implant Outcomes with Short-Term Aural Rehabilitation.

BACKGROUND: Increasing numbers of adults are receiving cochlear implants (CIs) and many achieve high levels of speech perception and improved quality of life. However, a proportion of implant recipients still struggle due to limited speech recognition and/or greater communication demands in their daily lives. For these individuals a program of aural rehabilitation (AR) has the potential to improve outcomes. PURPOSE: The study investigated the effects of a short-term AR intervention on speech recognition, functional communication, and psychosocial outcomes in post lingually deafened adult CI users. RESEARCH DESIGN: The experimental design was a multisite clinical study with participants randomized to either an AR treatment or active control group. Each group completed 6 weekly 90-minute individual treatment sessions. Assessments were completed pretreatment, 1 week and 2 months post-treatment. STUDY SAMPLE: Twenty-five post lingually deafened adult CI recipients participated. AR group: mean age 66.2 (48-80); nine females, four males; months postactivation 7.7 (3-16); mean years severe to profound deafness 18.4 (2-40). Active control group: mean age 62.8 (47-85); eight females, four males; months postactivation 7.0 (3-13); mean years severe to profound deafness 18.8 (1-55). INTERVENTION: The AR protocol consisted of auditory training (words, sentences, speech tracking), and psychosocial counseling (informational and communication strategies). Active control group participants engaged in cognitive stimulation activities (e.g., crosswords, sudoku, etc.). DATA COLLECTION AND ANALYSIS: Repeated measures ANOVA or analysis of variance, MANOVA or multivariate analysis of variance, and planned contrasts were used to compare group performance on the following measures: CasperSent; Hearing Handicap Inventory; Nijmegen Cochlear Implant Questionnaire; Client Oriented Scale of Improvement; Glasgow Benefit Inventory. RESULTS: The AR group showed statistically significant improvements on speech recognition performance, psychosocial function, and communication goals with no significant improvement seen in the control group. The two groups were statistically equivalent on all outcome measures at preassessment. The robust improvements for the AR group were maintained at 2 months post-treatment. CONCLUSION: Results of this clinical study provide evidence that a short-term AR intervention protocol can maximize outcomes for adult post lingually deafened CI users. The impact of this brief multidimensional AR intervention to extend CI benefit is compelling, and may serve as a template for best practices with adult CI users.

Cartilage conduction is characterized by vibrations of the cartilaginous portion of the ear canal.

Cartilage conduction (CC) is a new form of sound transmission which is induced by a transducer being placed on the aural cartilage. Although the conventional forms of sound transmission to the cochlea are classified into air or bone conduction (AC or BC), previous study demonstrates that CC is not classified into AC or BC (Laryngoscope 124: 1214-1219). Next interesting issue is whether CC is a hybrid of AC and BC. Seven volunteers with normal hearing participated in this experiment. The threshold-shifts by water injection in the ear canal were measured. AC, BC, and CC thresholds at 0.5-4 kHz were measured in the 0%-, 40%-, and 80%-water injection conditions. In addition, CC thresholds were also measured for the 20%-, 60%-, 100%-, and overflowing-water injection conditions. The contributions of the vibrations of the cartilaginous portion were evaluated by the threshold-shifts. For AC and BC, the threshold-shifts by the water injection were 22.6-53.3 dB and within 14.9 dB at the frequency of 0.5-4 kHz, respectively. For CC, when the water was filled within the bony portion, the thresholds were elevated to the same degree as AC. When the water was additionally injected to reach the cartilaginous portion, the thresholds at 0.5 and 1 kHz dramatically decreased by 27.4 and 27.5 dB, respectively. In addition, despite blocking AC by the injected water, the CC thresholds in force level were remarkably lower than those for BC. The vibration of the cartilaginous portion contributes to the sound transmission, particularly in the low frequency range. Although the airborne sound is radiated into the ear canal in both BC and CC, the mechanism underlying its generation is different between them. CC generates airborne sound in the canal more efficiently than BC. The current findings suggest that CC is not a hybrid of AC and BC.

Cartilage conduction efficiently generates airborne sound in the ear canal.

OBJECTIVE: By attaching a transducer to the aural cartilage, a relatively loud sound is audible even with a negligibly small fixation force. Previous study has identified several pathways for sound transmission by means of cartilage conduction. This investigation focused on the relative contribution of direct vibration of the aural cartilage to sound transmission in an open and in an occluded ear. METHODS: Thresholds with and without an earplug were compared for three experimental conditions: the transducer being placed on the tragus, pretragus, and mastoid. Eight volunteers with normal hearing participated. RESULTS: The thresholds increased with distance of the transducer from the ear canal (tragus, pretragus, mastoid, in that order). The differences were statistically significant for all conditions except for the occluded ear at 4 kHz. With the earplug inserted, the thresholds for the tragus condition were most sensitive below 2 kHz, indicating a significant contribution of direct vibration of the aural cartilage. CONCLUSION: Direct vibration of the aural cartilage can enhance sound transmission. At low frequencies, cartilage conduction can deliver sound efficiently across a blockage in the ear canal. Stray airborne sound radiating from the transducer dominates cartilage conduction in the open ear at high frequencies.

Optimizing Performance in Adult Cochlear Implant Users through Clinician Directed Auditory Training.

Clinician-directed auditory training using the KTH Speech Tracking Procedure can be a powerful approach for maximizing outcomes with adult cochlear implant (CI) users. This article first reviews prior research findings from an 8-week clinician-directed auditory training (AT) program using speech tracking that yielded significant gains in speech tracking rate and sentence recognition scores following training. The second focus of the article is to illustrate the value of intensive face-to-face long-term AT using speech tracking with adult CI users. A detailed case study report is presented that demonstrates major ongoing and progressive gains in tracking rate, sentence recognition, and improvements in self-perceived competence and confidence over the course of intensive long-term training. Given the potential of both short- and long-term clinician-directed auditory training via KTH speech tracking to help CI users reach their optimal performance level, consideration for more widespread clinical use is proposed in the overall rehabilitation of adult CI users.

Cartilage conduction hearing.

Sound information is known to travel to the cochlea via either air or bone conduction. However, a vibration signal, delivered to the aural cartilage via a transducer, can also produce a clearly audible sound. This type of conduction has been termed "cartilage conduction." The aural cartilage forms the outer ear and is distributed around the exterior half of the external auditory canal. In cartilage conduction, the cartilage and transducer play the roles of a diaphragm and voice coil of a loudspeaker, respectively. There is a large gap between the impedances of cartilage and skull bone, such that cartilage vibrations are not easily transmitted through bone. Thus, these methods of conduction are distinct. In this study, force was used to apply a transducer to aural cartilage, and it was found that the sound in the auditory canal was amplified, especially for frequencies below 2 kHz. This effect was most pronounced at an application force of 1 N, which is low enough to ensure comfort in the design of hearing aids. The possibility of using force adjustments to vary amplification may also have applications for cell phone design.

The clinical utility of expressing hearing thresholds in terms of the forward-going sound pressure wave.

OBJECTIVE: To assess the clinical utility of quantifying pure-tone hearing thresholds in terms of the forward-going sound pressure wave. DESIGN: Sound pressure measurements in the ear canal were used to derive, with hearing threshold measurements, hearing thresholds expressed in terms of the forward-going sound pressure wave, hearing thresholds based on coupler-based calibration, and hearing thresholds expressed in terms of the sound pressure measured at the microphone. STUDY SAMPLE: Fifty-two adults, 18 to 34 years of age, served as the study group. RESULTS: Audiogram configurations were similar up to 2000 Hz for the three expressions of hearing threshold, consistent with the ear canal acting as a simple volume up to this frequency. Above 2000 Hz, notable differences in hearing threshold were found, consistent with the acoustic input impedance of the ear differing from a rigid, hard-walled cavity. Repeat testing showed all three expressions of hearing threshold to be repeatable. High density measurements of hearing threshold from 3000 to 6000 Hz provided qualified support for the derivation of the forward-going sound pressure wave. CONCLUSIONS: Hearing thresholds expressed in terms of the forward-going sound pressure wave are repeatable, and with in-situ calibration, may be superior to the current coupler-based method.

Is cartilage conduction classified into air or bone conduction?

OBJECTIVES/HYPOTHESIS: The aim of this study was to establish the sound transmission characteristics of cartilage conduction proposed by Hosoi (2004), which is available by a vibration signal delivered to the aural cartilage from a transducer. STUDY DESIGN: Experimental study. METHOD: Eight volunteers with normal hearing participated. Thresholds at frequencies of 0.5, 1, 2, and 4 kHz for air conduction, bone, and cartilage conductions were measured with and without an earplug. The sound pressure levels on the eardrum at the threshold estimated with a Head and Torso Simulator were compared between air and cartilage conductions. The force levels calibrated with an artificial mastoid at the threshold were compared between bone and cartilage conductions. RESULTS: The difference in the estimated sound pressure levels on the eardrum at the thresholds between air and cartilage conductions were within 10 dB. In contrast, the force levels at the thresholds for cartilage conduction were remarkably lower than those for bone conduction. These findings suggested that sounds were probably transmitted via the eardrum for cartilage conduction. The threshold shifts by an earplug showed no significant difference between bone and cartilage conductions at 0.5 kHz. At 1 and 2 kHz, the threshold-shifts increased significantly in the order of bone, cartilage, and air conductions. These results suggested that airborne sound induced by the vibration of the cartilaginous portion of the ear canal played a significant role in sound transmission for cartilage conduction. CONCLUSIONS: Cartilage conduction has different characteristics from conventional air and bone conductions.

Speech comprehension training and auditory and cognitive processing in older adults.

PURPOSE: To provide a brief history of speech comprehension training systems and an overview of research on auditory and cognitive aging as background to recommendations for future directions for rehabilitation. METHOD: Two distinct domains were reviewed: one concerning technological and the other concerning psychological aspects of training. Historical trends and advances in these 2 domains were interrelated to highlight converging trends and directions for future practice. RESULTS: Over the last century, technological advances have influenced both the design of hearing aids and training systems. Initially, training focused on children and those with severe loss for whom amplification was insufficient. Now the focus has shifted to older adults with relatively little loss but difficulties listening in noise. Evidence of brain plasticity from auditory and cognitive neuroscience provides new insights into how to facilitate perceptual (re-)learning by older adults. CONCLUSIONS: There is a new imperative to complement training to increase bottom-up processing of the signal with more ecologically valid training to boost top-down information processing based on knowledge of language and the world. Advances in digital technologies enable the development of increasingly sophisticated training systems incorporating complex meaningful materials such as music, audiovisual interactive displays, and conversation.

Temporal integration of the contralateral acoustic reflex threshold for a 1000 hz tonal activator and its age-related changes.

BACKGROUND: Previous research has noted an age effect on the temporal integration of the acoustic reflex for a noise activator. PURPOSE: To determine whether the age effect earlier noted for a noise activator will be noted for a tonal activator. RESEARCH DESIGN: Comparison of ARTs of younger and older groups at activating stimulus durations of 12, 25, 50, 100, 200, 300, 500, and 1000 msec. STUDY SAMPLE: Two groups of adults with normal-hearing sensitivity: one group of 20 young adults (ten males and ten females, ages 18-29 years, with a mean age of 24 years) and one group of 20 older adults (ten males and ten females, ages 59-75 years, with a mean age of 67.5 years). RESULTS: A significant main effect for duration was obtained. That is, as the duration increased, the acoustic reflex threshold for the 1000 Hz tonal activator decreased. The interactions of duration x age group and duration x hearing level were not significant. There was a nonsignificant main effect (p = .889) for the between-subjects factor of age. CONCLUSION: Results contradict the findings for broadband noise.

Stuart Gatehouse: the international perspective.

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.

Effect of dual sensory loss on auditory localization: implications for intervention.

Our sensory systems are remarkable in several respects. They are extremely sensitive, they each perform more than one function, and they interact in a complementary way, thereby providing a high degree of redundancy that is particularly helpful should one or more sensory systems be impaired. In this article, the problem of dual hearing and vision loss is addressed. A brief description is provided on the use of auditory cues in vision loss, the use of visual cues in hearing loss, and the additional difficulties encountered when both sensory systems are impaired. A major focus of this article is the use of sound localization by normal hearing, hearing impaired, and blind individuals and the special problem of sound localization in people with dual sensory loss.

A historical perspective on digital hearing AIDS: how digital technology has changed modern hearing AIDS.

This article provides the author's perspective on the development of digital hearing aids and how digital signal processing approaches have led to changes in hearing aid design. Major landmarks in the evolution of digital technology are identified, and their impact on the development of digital hearing aids is discussed. Differences between analog and digital approaches to signal processing in hearing aids are identified.

Temporal integration of the contralateral acoustic-reflex threshold and its age-related changes.

Although numerous studies have investigated temporal integration of the acoustic-reflex threshold (ART), research is lacking on the effect of age on temporal integration of the ART. Therefore the effect of age on temporal integration of the ART was investigated for a broad-band noise (BBN) activator. Subjects consisted of two groups of adults with normal-hearing sensitivity: one group of 20 young adults (ten males and ten females, ages 18-29 years, with a mean age of 24 years) and one group of 20 older adults (ten males and ten females, ages 59-75 years, with a mean age of 67.5 years). Activating stimulus durations were 12, 25, 50, 100, 200, 300, 500, and 1000 ms. Significant main effects for duration and age were obtained. That is, as the duration increased, the acoustic reflex threshold for BBN decreased. The interactions of duration x age group and duration x hearing level were not significant. The result of pair-wise analysis indicated statistically significant differences between the two age groups at durations of 20 ms and longer. The observed age effect on temporal integration of the ART for the BBN activator is interpreted in relation to senescent changes in the auditory system.

Evaluation of human middle ear function via an acoustic power assessment.

Measurements of middle ear (ME) acoustic power flow (power reflectance, power absorption, and transmittance) and normalized impedance (acoustic resistance, acoustic reactance, and impedance magnitude) were compared for their utility in clinical applications. Transmittance, a measure of the acoustic power absorbed by the ME, was found to have several important advantages over other measures of acoustic power flow. In addition to its simple and audiologically relevant physical interpretation (absorbed power), the normal transmittance curve has a simple shape that is visually similar to the ME transfer function. The acoustic impedance measures (resistance and reactance) provided important additional information about ME status and supplemented transmittance measurements. Together these measurements can help identify unusual conditions such as eardrum perforations. While this article is largely a review of the development of a commercial power reflectance measurement system, previously unpublished experimental results are presented.

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

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

Studies with Digital Hearing Aids.

Digital hearing aids offer many advantages over conventional hearing aids. These include signal-processing capabilities that are superior to those of a conventional analog hearing aid, methods of signal-processing and control that are unique to digital systems and which cannot be implemented in conventional analog hearing aids, and innovative new techniques that are changing our way of thinking about hearing aids. An example of the first of these advantages is the extremely high precision with which the frequency-gain characteristic can be specified and the use of this capability to study the effects of frequency response irregularities commonly encountered with hearing aids. An example of the second advantage is the use of memory and logical operations in the implementation of multivariate adaptive paired-comparison techniques for more effective hearing-aid prescription. Another example is the use of powerful new signal processing techniques for noise reduction. The third advantage is the most important. The digital hearing aid can be viewed as a generalized hearing instrument which can be used for simulation, testing and prescription, as well as amplification. The use of the digital hearing aid as a simulator of other hearing aids is discussed and an illustrative example provided in which a new form of amplitude compression, orthogonal-polynomial compression, has been simulated using a digital master hearing aid.