PubMed Health⌕ Search

Biomedical subjects

J Barfod

Publications and source records attributed to J Barfod.

6 recordsLinked to original sources
PubMed1979

Speech perception processes and fitting of hearing aids.

A model of speech perception is modified to take into account the adaptational factors involved in speech perception and learning. In connection with fitting of hearing aids, the model permits a description and identification of factors influencing the immediate and long-term benefits of a hearing aid. Various aspects of the model in connection with the rehabilitation process using hearing aids are considered and a new step-wise adjusting procedure for the assessment of hearing aids is proposed. Our observations imply that speech audiometry is a poor indicator of the long-term benefit of a hearing aid.

Audiometry, Speech↗
PubMed1978

Estimation of the critical bandwidth from loudness summation data.

An automatic method for critical band estimation from loudness summation data is presented. A mathematical model, based on a power function, is fitted to the data and the critical bandwidth is defined at the intersection of the asymptotes. The model is designed for clinical use, involving the treatment of the data from single test persons; it represents an operational solution to a difficult task. The model is able to describe data from normals and patients with a sensorineural hearing loss. Variability of the critical band estimates, intrasubject as well as intersubject, is larger than for visually obtained estimates. However, visual estimation is difficult, subjective, and probably heavily biased. The model produces estimates which in logarithmic form have a Normal distribution at medium loudness level, while visual estimation gives rise to irregular distributions at all levels. A normal range for model estimates from sets of data obtained at medium loudness level is defined by mean and standard deviation.

Auditory Perception↗
PubMed1978

Multichannel compression hearing aids: experiments and consideration on clinical applicability.

The rational for applying multichannel compression in connection with peripheral perceptive hearing loss is briefly discussed. The speech transfer ability of a multichannel compression hearing aid with up to 4 channels is evaluated on high tone hearing impaired subjects. The compression characteristic of each channel is individually fitted to compensate on average the loudness recruitment of the subject's hearing within each individually determined frequency band. Experiments on 5 subjects under several signal-to-noise ratio conditions reveal that 4-channel recruitment compensation is indistinguishable in performance from an "optimally" fitted linear hearing aid which takes advantage of the limited dynamic range of the applied speech signal. Contrarily, 3- and 2-channel configurations investigated show in general degraded performance on speech compared to this condition. The results obtained and their implications for the design objectives of future multichannel compression hearing aids and the clinical fitting of such an aid are discussed.

Adult↗
PubMed1978

Automatic regulation systems with relevance to hearing aids.

Compression amplification in hearing aids has gained much interest in the recent years. Other types of nonlinear signal processing in hearing aids are developing. The principles of nonlinear signal processing through automatic regulation, as opposed to instanteaneously acting nonlinear signal transfer, is described in general. In particular the properties and terminology of amplitude compression and limiting circuits in relation to hearing aids are discussed. Several examples are given of nonlinear regulation systems for hearing aids involving other features than amplitude compression.

Acoustics↗
PubMedDate not supplied

A new concept of vertex ERA and EEG analysis applying inverse filtering.

Evidence for a common anatomical and physiological substrate for the generation of the background EEG and the vertex-evoked response led to the hypothesis that the EEG can be interpreted as the output from a time varying filter driven by (a) a noise generator responsible for the background activity, and (b) a pulse generator creating the evoked response. The characteristics of the filter can be estimated by autoregression. The application of such a model results in considerable theoretical and practical improvements in the detection of evoked responses. Selected averaging on EEGs classified according to the filter characteristics shows improved S/N ratios and considerable diversity between classes. Investigations of an estimate of the input signal to the filter, derived by deconvolution, reveal a sound-evoked potential which is less variable than the response in the EEG. The study concludes that the proposed model and methods have a sufficient applicability and physiological relevance to support further developments.

Audiometry↗