Trends in Amplification最新文献

Perceptual training with spectrally degraded environmental sounds results in improved environmental sound identification, with benefits shown to extend to untrained speech perception as well. The present study extended those findings to examine longer-term training effects as well as effects of mere repeated exposure to sounds over time. Participants received two pretests (1 week apart) prior to a week-long environmental sound training regimen, which was followed by two posttest sessions, separated by another week without training. Spectrally degraded stimuli, processed with a four-channel vocoder, consisted of a 160-item environmental sound test, word and sentence tests, and a battery of basic auditory abilities and cognitive tests. Results indicated significant improvements in all speech and environmental sound scores between the initial pretest and the last posttest with performance increments following both exposure and training. For environmental sounds (the stimulus class that was trained), the magnitude of positive change that accompanied training was much greater than that due to exposure alone, with improvement for untrained sounds roughly comparable to the speech benefit from exposure. Additional tests of auditory and cognitive abilities showed that speech and environmental sound performance were differentially correlated with tests of spectral and temporal-fine-structure processing, whereas working memory and executive function were correlated with speech, but not environmental sound perception. These findings indicate generalizability of environmental sound training and provide a basis for implementing environmental sound training programs for cochlear implant (CI) patients.

Low-frequency otoacoustic emissions (OAEs) are often concealed by acoustic background noise such as those from a patient's breathing and from the environment during recording in clinics. When using electrocochleaography (ECochG or ECoG), such as cochlear microphonics (CMs), acoustic background noise do not contaminate the recordings. Our objective is to study the response pattern of CM waveforms (CMWs) to explore an alternative approach in assessing cochlear functions. In response to a 14-msec tone burst across several acoustic frequencies, CMWs were recorded at the ear canal from ten normal hearing subjects. A relatively long tone burst has a relatively narrow frequency band. The CMW amplitudes among different frequencies were compared. The CMW amplitudes among different frequencies were compared. Two features were observed in the response pattern of CMWs: the amplitude of CMWs decreased with an increase of stimulus frequency of the tone bursts; and such a decrease occurred at a faster rate at lower frequencies than at higher frequencies. Five factors as potential mechanisms for these features are proposed. Clinical applications such as hearing screening are discussed. Therefore, the response pattern of CMWs suggests that they may be used as an alternative to OAEs in the assessment of cochlear functions in the clinic, especially at low frequencies.

To restore hearing sensation, cochlear implants deliver electrical pulses to the auditory nerve by relying on sophisticated signal processing algorithms that convert acoustic inputs to electrical stimuli. Although individuals fitted with cochlear implants perform well in quiet, in the presence of background noise, the speech intelligibility of cochlear implant listeners is more susceptible to background noise than that of normal hearing listeners. Traditionally, to increase performance in noise, single-microphone noise reduction strategies have been used. More recently, a number of approaches have suggested that speech intelligibility in noise can be improved further by making use of two or more microphones, instead. Processing strategies based on multiple microphones can better exploit the spatial diversity of speech and noise because such strategies rely mostly on spatial information about the relative position of competing sound sources. In this article, we identify and elucidate the most significant theoretical aspects that underpin single- and multi-microphone noise reduction strategies for cochlear implants. More analytically, we focus on strategies of both types that have been shown to be promising for use in current-generation implant devices. We present data from past and more recent studies, and furthermore we outline the direction that future research in the area of noise reduction for cochlear implants could follow.

The present article reports on the perceptual weighting of prosodic cues in question-statement identification by adult cochlear implant (CI) listeners. Acoustic analyses of normal-hearing (NH) listeners' production of sentences spoken as questions or statements confirmed that in English the last bisyllabic word in a sentence carries the dominant cues (F0, duration, and intensity patterns) for the contrast. Furthermore, these analyses showed that the F0 contour is the primary cue for the question-statement contrast, with intensity and duration changes conveying important but less reliable information. On the basis of these acoustic findings, the authors examined adult CI listeners' performance in two question-statement identification tasks. In Task 1, 13 CI listeners' question-statement identification accuracy was measured using naturally uttered sentences matched for their syntactic structures. In Task 2, the same listeners' perceptual cue weighting in question-statement identification was assessed using resynthesized single-word stimuli, within which fundamental frequency (F0), intensity, and duration properties were systematically manipulated. Both tasks were also conducted with four NH listeners with full-spectrum and noise-band-vocoded stimuli. Perceptual cue weighting was assessed by comparing the estimated coefficients in logistic models fitted to the data. Of the 13 CI listeners, 7 achieved high performance levels in Task 1. The results of Task 2 indicated that multiple sources of acoustic cues for question-statement identification were utilized to different extents depending on the listening conditions (e.g., full spectrum vs. spectrally degraded) or the listeners' hearing and amplification status (e.g., CI vs. NH).

Low utilization of hearing aids has drawn increased attention to the study of consumer preferences using both simple ratings (e.g., Likert scale) and conjoint analyses, but these two approaches often produce inconsistent results. The study aims to directly compare Likert scales and conjoint analysis in identifying important attributes associated with hearing aids among those with hearing loss. Seven attributes of hearing aids were identified through qualitative research: performance in quiet settings, comfort, feedback, frequency of battery replacement, purchase price, water and sweat resistance, and performance in noisy settings. The preferences of 75 outpatients with hearing loss were measured with both a 5-point Likert scale and with 8 paired-comparison conjoint tasks (the latter being analyzed using OLS [ordinary least squares] and logistic regression). Results were compared by examining implied willingness-to-pay and Pearson's Rho. A total of 56 respondents (75%) provided complete responses. Two thirds of respondents were male, most had sensorineural hearing loss, and most were older than 50; 44% of respondents had never used a hearing aid. Both methods identified improved performance in noisy settings as the most valued attribute. Respondents were twice as likely to buy a hearing aid with better functionality in noisy environments (p < .001), and willingness to pay for this attribute ranged from US$2674 on the Likert to US$9000 in the conjoint analysis. The authors find a high level of concordance between the methods-a result that is in stark contrast with previous research. The authors conclude that their result stems from constraining the levels on the Likert scale.

In vertebrates, perception of sound, motion, and balance is mediated through mechanosensory hair cells located within the inner ear. In mammals, hair cells are only generated during a short period of embryonic development. As a result, loss of hair cells as a consequence of injury, disease, or genetic mutation, leads to permanent sensory deficits. At present, cochlear implantation is the only option for profound hearing loss. However, outcomes are still variable and even the best implant cannot provide the acuity of a biological ear. The recent emergence of stem cell technology has the potential to open new approaches for hair cell regeneration. The goal of this review is to summarize the current state of inner ear stem cell research from a viewpoint of its clinical application for inner ear disorders to illustrate how complementary studies have the potential to promote and refine stem cell therapies for inner ear diseases. The review initially discusses our current understanding of the genetic pathways that regulate hair cell formation from inner ear progenitors during normal development. Subsequent sections discuss the possible use of endogenous inner ear stem cells to induce repair as well as the initial studies aimed at transplanting stem cells into the ear.

Two methods of fine tuning the initial settings of hearing aids were compared: An audiologist-driven approach--using real ear measurements and a patient-driven fine-tuning approach--using feedback from real-life situations. The patient-driven fine tuning was conducted by employing the Amplifit(®) II system using audiovideo clips. The audiologist-driven fine tuning was based on the NAL-NL1 prescription rule. Both settings were compared using the same hearing aids in two 6-week trial periods following a randomized blinded cross-over design. After each trial period, the settings were evaluated by insertion-gain measurements. Performance was evaluated by speech tests in quiet, in noise, and in time-reversed speech, presented at 0° and with spatially separated sound sources. Subjective results were evaluated using extensive questionnaires and audiovisual video clips. A total of 73 participants were included. On average, higher gain values were found for the audiologist-driven settings than for the patient-driven settings, especially at 1000 and 2000 Hz. Better objective performance was obtained for the audiologist-driven settings for speech perception in quiet and in time-reversed speech. This was supported by better scores on a number of subjective judgments and in the subjective ratings of video clips. The perception of loud sounds scored higher than when patient-driven, but the overall preference was in favor of the audiologist-driven settings for 67% of the participants.

Functional simulation of sensorineural hearing impairment is an important research tool that can elucidate the nature of hearing impairments and suggest or eliminate compensatory signal-processing schemes. The objective of the current study was to evaluate the capability of an audibility-based functional simulation of hearing loss to reproduce the auditory-filter characteristics of listeners with sensorineural hearing loss. The hearing-loss simulation used either threshold-elevating noise alone or a combination of threshold-elevating noise and multiband expansion to reproduce the audibility-based characteristics of the loss (including detection thresholds, dynamic range, and loudness recruitment). The hearing losses of 10 listeners with bilateral, mild-to-severe hearing loss were simulated in 10 corresponding groups of 3 age-matched normal-hearing listeners. Frequency selectivity was measured using a notched-noise masking paradigm at five probe frequencies in the range of 250 to 4000 Hz with a fixed probe level of either 70 dB SPL or 8 dB SL (whichever was greater) and probe duration of 200 ms. The hearing-loss simulation reproduced the absolute thresholds of individual hearing-impaired listeners with an average root-mean-squared (RMS) difference of 2.2 dB and the notched-noise masked thresholds with an RMS difference of 5.6 dB. A rounded-exponential model of the notched-noise data was used to estimate equivalent rectangular bandwidths and slopes of the auditory filters. For some subjects and probe frequencies, the simulations were accurate in reproducing the auditory-filter characteristics of the hearing-impaired listeners. In other cases, however, the simulations underestimated the magnitude of the auditory bandwidths for the hearing-impaired listeners, which suggests the possibility of suprathreshold deficits.

A self-fitting, self-contained hearing aid is a device that can be managed entirely by the user, without assistance from a hearing health care professional or the need for special equipment. A key component of such a device is an automated audiometer that will enable the user to self-administer measurements of in situ thresholds, which the hearing aid will use to prescribe a baseline setting for the wearer. The success of the device therefore depends on the validity and reliability of in situ threshold measurements and automatically measured thresholds. To produce a complete and self-contained device, the self-fitting hearing aid will also enable identification of audiograms that are contraindicative of hearing aid usage. The feasibility and challenges of achieving these characteristics are explored and discussed. While the overall concept seems feasible, several challenges were identified that need thorough investigation and/or development. These include the use of instructions to self-manage hearing aid insertion and in situ threshold measurements, selection of an appropriate transducer and instant-fit tip that will allow measurements of a wide range of threshold levels, control of ambient noise during threshold measurements, and self-manageable procedures that enable identification of such audiogram characteristics as asymmetry and conductive hearing loss.