British journal of audiology最新文献

The increasing use of transiently evoked otoacoustic emissions (TEOAE) in large neonatal hearing screening programmes makes a standardized method of response classification desirable. Until now methods have been either subjective or based on arbitrary response characteristics. This study takes an expert system approach to standardize the subjective judgements of an experienced scorer. The method that is developed comprises three stages. First, it transforms TEOAEs from waveforms in the time domain into a simplified parameter set. Second, the parameter set is classified by an artificial neural network that has been taught on a large database TEOAE waveforms and corresponding expert scores. Third, additional fuzzy logic rules automatically detect probable artefacts in the waveforms and synchronized spontaneous emission components. In this way, the knowledge of the experienced scorer is encapsulated in the expert system software and thereafter can be accessed by non-experts. Teaching and evaluation of the neural network was based on TEOAEs from a database totalling 2190 neonatal hearing screening tests. The database was divided into learning and test groups with 820 and 1370 waveforms respectively. From each recorded waveform a set of 12 parameters was calculated, representing signal static and dynamic properties. The artifical network was taught with parameter sets of only the learning groups. Reproduction of the human scorer classification by the neural net in the learning group showed a sensitivity for detecting screen fails of 99.3% (299 from 301 failed results on subjective scoring) and a specificity for detecting screen passes of 81.1% (421 of 519 pass results). To quantify the post hoc performance of the net (generalization), the test group was then presented to the network input. Sensitivity was 99.4% (474 from 477) and specificity was 87.3% (780 from 893). To check the efficiency of the classification method, a second learning group was selected out of the previous test group, and the previous learning group was used as the test group. Repeating learning and test procedures yielded 99.3% sensitivity and 80.7% specificity for reproduction, and 99.4% sensitivity and 86.7% specificity for generalization. In all respects, performance was better than for a previously optimized method based simply on cross-correlation between replicate non-linear waveforms. It is concluded that classification methods based on neural networks show promise for application to large neonatal screening programmes utilizing TEOAEs.

Evoked otoacoustic emissions are well established as a hearing screening technique and are used extensively in paediatric audiology. They are believed to originate from the outer hair cells and can be detected in almost 100% of normally hearing ears; even a mild hearing loss has been shown to abolish otoacoustic emissions. Results are presented of a baby boy born at 29 weeks' gestation requiring 77 days of neonatal care, but experiencing no complications following discharge from the neonatal unit. This child had clear bilateral evoked otoacoustic emissions at almost four months of age, but was subsequently found to have a profound bilateral hearing impairment and absent otoacoustic emissions. Radiological investigations revealed bilateral Mondini dysplasia, and this child has now been implanted with a multi-channel MXM Digisonic cochlear implant. He is progressing well and shows awareness of sound. Approximately 10 previous cases of otoacoustic emissions occurring in profoundly deaf ears have been reported in the literature. Although it is likely that this child's hearing loss was progressive in nature, the authors believe that this is the first reported case of otoacoustic emissions being recorded in the presence of Mondini dysplasia. This raises concerns about the use of neonatal screening in isolation without adequate mechanisms for later identification of hearing impairment, although it is acknowledged that it represents a rare situation.

Tinnitus is a prevalent condition which has no practical and effective pharmacological treatment. In the absence of relief by conventional routes, sufferers are increasingly turning to 'alternative' or 'complementary' medicine. This paper reports the evaluation of a homeopathic preparation 'Tinnitus' by a double-blind, placebo-controlled clinical trial. The remedy was taken in tablet form at a homeopathic D60 potency. Perceived intensity and intrusiveness of the tinnitus was assessed at four points during the trial by subjective procedures (visual analogue scales and questionnaires) and by a battery of audiological measurements. Although questionnaire responses indicated that the homeopathic preparation was preferred to placebo by 14 of the 28 subjects, an analysis of variance indicated that neither the VAS scores nor the audiological measures showed significant improvement in tinnitus symptoms in response to 'Tinnitus' versus the placebo. It was concluded that 'Tinnitus' could not be shown to be more effective than the matched placebo.

Hearing aids with multi-channel compression are often fitted on the basis of loudness scaling data obtained using narrow bands of noise or tones. Here, we report the development and evaluation of an alternative fitting procedure based on the use of speech signals. The parameters of the hearing aid (the gains in each channel for high and low input levels) are adjusted adaptively under computer control on the basis of the listener's responses. The goal is that speech at 85 dB SPL should be judged as 'loud', speech at 60 dB SPL should be judged as 'quiet', and speech at both levels should be judged as 'neither tinny nor boomy'. The procedure was evaluated using a two-channel compression hearing aid, the remote control of which allowed two programs to be stored. One program was based on our fitting procedure. The other was either based on the manufacturer's recommended full fitting procedure (which included loudness scaling with bands of noise), or was based on the audiogram alone, using the manufacturer's algorithm. After an acclimatization period of at least two weeks, subjects were then asked to fill in a questionnaire about their experiences with the two programs in different listening situations. The results generally indicated a preference for the program based on our adaptive fitting procedure. We also conducted laboratory measurements of speech intelligibility, in quiet and in a background of a single competing talker. These showed no clear difference between programs, although scores overall were very high. We conclude that our adaptive procedure gives very satisfactory results in everyday life. Parameter values giving good comfort also give good intelligibility. The procedure typically takes between five and 10 minutes per ear, which is quicker than most loudness scaling procedures.

This study was designed to investigate earlier observations that probe-tube microphone measurements of insertion gain overestimates the functional gain received from hearing aids by users with significant conductive hearing losses. This was originally thought to be due to artefacts in the probe-tube measurement caused by middle ear pathology, but is now believed to be the result of the bone conduction stimulation of the ear exposed to high intensities of airborne sound during sound field threshold measurements. Since the functional gain must relate to the true aided benefit in such cases, these findings suggest that probe-tube microphone measurements in ears with significant air-bone gaps should be interpreted with caution.

Although hearing aid fitting by insertion gain measurement is known to be an accurate and reliable technique, it is rarely used routinely in the UK National Health Service (NHS) because of high demands on staff and time. This study investigated whether an alternative, more practical procedure of fitting by median ear corrected coupler measurements would be as beneficial to NHS patients. Forty patients took part in a double-blind cross-over study comparing the two fitting methods. Results show that the insertion gain fittings were significantly better than the coupler fittings in terms of both patient preference and speech discrimination in noise. It is concluded that, even with the limited response adjustments available, individual deviations from the median ear make routine hearing aid fitting by insertion gain measurement indeed desirable in the NHS.

As the distance between two communicators increases, weaker sounds of speech become inaudible, conversation becomes more difficult and there is a greater need to resolve communication difficulties. This study investigated the effects of distance on face-to-face social conversation by 27 older adults with hearing impairment, under three listening conditions (without amplification, with personal hearing aids, with a small portable amplifier). Each participant was rated on a 1-5 scale of conversational fluency at distances between 0.5 and 3.0 metres. Results indicate that the subjects conversed more fluently with amplification and at short communication distances. Use of a portable amplifier resulted in high conversational fluency regardless of distance.