Audiology : official organ of the International Society of Audiology最新文献

This paper investigated the performance of an optimal bandpass filtering technique to effectively identify click evoked otoacoustic emissions in neonates. The frequency response of the filter was optimized by maximizing the correlation coefficient between two replicate recordings (reproducibility). The optimal cut-off frequencies were also set by controlling the maximum energy loss after filtering to stop the crucial response contents being filtered along with the noise. As an additional constraint, the cut-off frequencies were forced to be outside the range of 1.6 to 4.2 kHz to avoid (in a response identification task) the spontaneous otoacoustic emissions from polarizing the cut-offs and thereby filtering fundamental frequency components, thus leading to an erroneous response classification. The best performance of the optimal filter in terms of increasing the post-filtering reproducibility was obtained when the procedure was applied to recordings whose reproducibility before filtering ranged between 60 and 80 per cent, i.e. for responses classified in most cases as partial pass.

In this study speech intelligibility in background noise was evaluated with 10 binaural hearing-aid users for hearing aids with one omnidirectional microphone and a hearing aid with a two-microphone configuration (enabling an omnidirectional as well as a directional mode). Signal-to-noise ratio (SNR) measurements were carried out for three different types of background noise (speech-weighted noise, traffic noise and restaurant noise) and two kinds of speech material (bisyllabic word lists and sentences). The average SNR improvement of the directional microphone configuration relative to the omnidirectional one was 3.4 dB for noise presented from 90 degrees azimuth. This improvement was independent of the specific type of noise and speech material, indicating that one speech-in-noise condition may yield enough relevant information in the evaluation of directional microphones and speech understanding in noise.

Open set speech understanding with cochlear implants, without speechreading, is nowadays a common finding. However, there is a large variation in speech understanding between cochlear implant users. We tried to find pre-operative parameters which predicted the post-operative results. Thirty-seven adult post-lingually deafened Nucleus cochlear implant users with a mean age of 46 years (range 16 68) and a mean duration of deafness of 15 years (range 1.5-47) were studied. Pre-operatively, we performed pure-tone audiometry, round window and ear canal electrical stimulation, psychological tests and imaging. Additionally, we measured pre-operatively speech understanding in the auditory, the visual and the audiovisual conditions with several tests which were also administered after 6 and 12 months' implant experience. Correlation analysis between the pre-operative variables and the post-operative factors showed that duration of deafness and residual hearing are the most important predictors. The temporal difference limen in pre-operative round window electrical stimulation is a secondary predictor.

Sound localization in subjects with chronic otitis media (COM) was examined before and soon after ear surgery by means of virtual sound presented by headphones, sound being synthesized based on the head-related transfer functions (HRTFs) in a normal subject. The localization ability in COM patients was usually worse than that in normal subjects, but was better than expected when compared with cases of acute loss. On the other hand, the effects of hearing improvement on localization ability observed in COM patients were smaller than those of simulated acute hearing loss achieved by earplugs in normal subjects. This seems to suggest that the localization cues in patients with chronic hearing loss are different from those under normal conditions.

A total of 150 full-term and 66 pre-term infants were selected at birth and prospectively examined at three-monthly intervals from birth until the age of 27 months. Parental reports of middle ear infection and/or hearing impairment were obtained prior to otoscopic and audiometric evaluation. The relationships between parental reports and the diagnoses acute otitis media (AOM), otitis media with effusion (OME) and hearing impairment (HI), were assessed in terms of sensitivity, specificity and positive and negative predictive values, using the data obtained during the follow-up period. AOM and OME were diagnosed using otoscopy and tympanometry. Hearing was assessed by conditioned orientation reflex audiometry. HI was defined as averaged thresholds > or = 20 dB compared with age-appropriate response levels. Despite the repeated feedback which parents received on the middle ear condition and hearing of their infants, the majority fail to recognize the presence of AOM, OME and HI. The limited sensitivity of parental reporting should discourage both researchers and clinicians from using it as a diagnostic or monitoring instrument, but they should not disregard parental concern when confronted with it.

In this study we measured the efficacy of a digital hearing aid with compression and noise reduction in a well-controlled clinical field trial in two independent centres. The experiments focused on a number of aspects of the application of the digital hearing aids. The study combines a field test of 2x4 weeks with laboratory experiments. We used objective measurements (speech perception tests in background noise, loudness scaling) and subjective assessments (questionnaires). The measurements were performed before and after the field test. The questionnaires were collected after each field test. The results of the digital hearing aids were compared to the results of similar tests with newly fitted analogue reference aids. The study involved 27 sensorineural hearing-impaired subjects, wearing new hearing aids. They comprised a representative sample of in-the-ear users. We used a crossover design in which the subjects used successively digital hearing aids and analogue reference aids in a randomized order. On average, the subjective data are more positive than the objective data. In the end, 20 out of 27 subjects had an overall preference for the digital hearing aid. The financial implications were not taken into consideration. However, objective data do not support this strong subjective preference. A reason could be that the method of analysis (short sentences in a short-duration background noise) is not suited for the digital hearing aid; the testing procedure does not allow the noise-reduction algorithm to adapt to the background noise. There was a striking difference between the results for the two centres. This difference can, to at least a certain extent, be attributed to the timing of speech relative to the background noise in the objective tests. This illustrates that the test conditions are critical in modern non-linear signal-processing hearing aids with long time constants. New evaluation techniques should be developed for this new generation of active non-linear hearing aids.

Seven hundred and forty seven elderly people aged from 65 to 98 (209 male and 538 female) admitted to the Geriatric Health Service Facility were evaluated with pure-tone audiometry, Office of Population Censuses and Surveys (OPCS) personal care severity score, OPCS hearing severity score, Mini-mental State Examination (MMSE) and Self-rating Depression Scale (SDS). A single correlation study indicated that the hearing level significantly correlated with age, OPCS hearing severity score, MMSE total score and SDS total score. A multiple regression analysis showed that age, OPCS hearing severity score, and MMSE total score were significantly associated with the hearing level. We demonstrated here that the objective auditory function strongly correlated with the cognitive function measured by MMSE total score, suggesting that a regular audiological check-up and the early detection of the hearing impairment could contribute to the maintenance of the quality of life in the elderly.

The intent of this study was to compare the effectiveness of continuous versus gated contralateral noise in producing efferent suppression of CAPs in guinea pigs. The average contralateral suppression was 2.0 dB when using gated noise, with ipsilateral tone-pip rates of 2 s(-1), and 1.4 dB when using continuous noise at an ipsilateral tone-pip rate of 31 s(-1). When the ipsilateral tone-pip rate employed in the simultaneous paradigm with continuous noise was reduced to 2 s(-1), a rate equivalent to that employed in the non-simultaneous paradigm, the average attenuation was 2.1 dB, a magnitude comparable to the suppression achieved using gated noise. The present data suggest that, when equated for ipsilateral tone-pip pulse rate, simultaneous and non-simultaneous contralateral masking paradigms produce comparable levels of efferent suppression.

The effects of ambient noise and averaging time on distortion product otoacoustic emission (DPOAE) measurements were systematically examined in 20 normally hearing adults. For each frequency from 0.7 to 6 kHz, 2f1-f2 DPOAEs were measured at nine intensity levels of ambient noise for each of four different averaging times. The dependent variable of interest was the DPOAE:noise ratio (D:N)--the relationship between DPOAE amplitude and noise level at 2f1-f2. Findings indicated that, relative to the baseline condition (25 dBA), ambient noise levels of 40 dBA or greater affected the D:N considerably in the lower frequencies. However, noise levels of 55-65 dBA did not affect the D:N in the higher frequencies. Results also indicated that, to achieve detectable DPOAEs, longer averaging times were required as ambient noise increased and as frequency decreased. Based on the results, the maximum permissible ambient noise levels (MPANLs) were estimated in relation to averaging time.