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Biomedical subjects

B Hagerman

Publications and source records attributed to B Hagerman.

11 recordsLinked to original sources
PubMed1992

Perceived sound quality in a hearing aid with vented and closed earmould equalized in frequency response.

Nine normal-hearing subjects listened to speech and music in a hearing aid, either through a vented earmould or a closed earmould. The complex frequency responses of the two systems were made equal by compensating the aid and closed mould combination with a digital filter. The subjects rated the perceived sound quality of the systems on seven perceptual scales and a scale for overall impression. The results of the ratings support the hypothesis that there is no difference in perceived sound quality between vented and closed earmoulds that are equalized in frequency response, provided that the perceived loudness is the same in both cases.

Acoustic Stimulation↗
PubMed1990

Perceived sound quality of reproductions with different frequency responses and sound levels.

Three programs (female voice, jazz music, and pink noise) were reproduced using four different frequency responses and two different sound levels. Fourteen normal hearing subjects listened to the reproduction via earphones and judged the sound quality on seven perceptual scales (loudness, clarity, fullness, spaciousness, brightness, softness/gentleness, and nearness) and a fidelity scale. Significant differences among the reproductions appeared in all scales and could be attributed to the differences in frequency response or sound level or both. Interactions between the reproductions and the programs could be explained by the relations between the spectrum of the programs and the frequency responses used. The results for the noise program were similar to those for the jazz music program.

Adult↗
PubMed1989

To find the PB max--simulations of Levitt's adaptive method.

Levitt's (Scand Audiol 1978;6(Suppl):241-291) adaptive method for finding the speech level giving the maximum speech recognition score (PB max) was simulated in a computer. The results show that at least 50 words should be used to estimate the speech level at PB max before measuring the speech recognition at that level. The choice of stepping parameters is critical. Within a word pair, a 20 dB level difference is suggested. Scatter plots show the variability in the measured speech levels. The variability of conventional speech recognition measurements is also clearly illustrated.

Computer Simulation↗
PubMed1988

The effects of different frequency responses on sound quality judgments and speech intelligibility.

Four speech programs and two music programs were reproduced using five different frequency responses: one flat and the others combinations of reductions at lower frequencies and/or increases at higher frequencies. Twelve hearing impaired (HI) and 8 normal hearing (NH) subjects listened monaurally to the reproductions at comfortable listening level and judged the sound quality on seven perceptual scales and a scale for total impression. Speech intelligibility was measured for phonetically balanced (PB) word lists and for sentences in noise. Significant differences among the reproductions appeared in practically all scales. The most preferred system was characterized by a flat response at lower frequencies and a 6 dB/octave increase thereafter. There were certain differences between the NH and HI listeners in the judgments of the other systems. The intelligibility of PB word lists did not differ among the systems, and the S/N threshold for the sentences in noise only distinguished the flat response as worse than all others for the HI listeners. There was little correspondence between intelligibility measures and sound quality measures. The latter provided more information and distinctions among systems.

Adult↗
PubMed1987

Relations between speech intelligibility and psychoacoustical modulation transfer function (PMTF).

The modulation transfer function, MTF, has proved to be a powerful measure for predicting speech intelligibility in speech transmission channels. We extended it to include the ear, by measuring the psycho-acoustical MTF, i.e. the PMTF. Tone thresholds of 11 normal-hearing and 20 hearing-impaired subjects were measured in presence of unmodulated and intensity modulated noise. Octave frequencies from 500 to 4,000 Hz were used. The noise was octave filtered around the frequency of the probe tone. Six modulation frequencies from 1 to 50 Hz were used. From these results the PMTFs were calculated, as well as the corresponding psycho-acoustical speech transmission indices, i.e. the PSTIs. The subjects' speech discrimination scores in quiet and speech reception thresholds in noise were also measured. A correlation coefficient of 0.85 between the speech discrimination score in quiet and the PSTI was obtained. For the speech reception threshold in noise and the PSTI, the correlation was 0.71. The first of these two figures is promising, but our method needs some improvement, as it gave some problems due to fatigue effects.

Hearing Loss, Sensorineural↗
PubMed1985

Questionnaires on desirable properties of hearing aids.

Three questionnaires were presented to 49 hearing-impaired patients. They were asked to rank different properties of behind-the-ear hearing aids with regard to their importance. The first questionnaire dealt with physical properties such as size, weight, and battery-cost, but also with the importance of good sound quality. The second questionnaire focused on the relative importance of various sound quality dimensions, such as softness, clarity, fullness, and others. The third questionnaire asked for suitable sound programs to be used in the procedure of hearing aid fitting in the clinic. Sound quality scored the highest rank by 43 of the patients, and clarity was considered to be the most important sound quality dimension. The most preferred sound programs included male and female voices with or without a background of other voices.

Adolescent↗
PubMed1984

A clinical comparison between a laboratory and a commercial impedance audiometer.

Impedance audiometry is a useful tool in the diagnosis of retrocochlear lesions, provided that adequate normal values regarding the stapedius reflex thresholds and decay are used. The normal values in Sweden (and elsewhere) have been obtained with a laboratory impedance audiometer that is not in common use. We have compared a commercial impedance audiometer, the Grason-Stadler 1723, with this laboratory model to determine whether the normal values are valid. We found that the Grason-Stadler 1723 audiometer gives reliable stapedius reflex thresholds, but at 2-4 dB higher levels. The reflex decay curves, however, are unsatisfactory. Possible explanations for the results are discussed. We have also proposed a modification of the recorder of the commercial audiometer. The study demonstrates that normal values cannot be transferred freely between different equipments.

Acoustic Impedance Tests↗
PubMed1984

Clinical measurements of speech reception threshold in noise.

New lists of spoken sentences, edited in a computer, word by word, were tested clinically together with a noise, spectrally shaped as the speech. The purpose was to investigate the reliability and the learning effect of the speech reception threshold in noise, and also to assess the relations of this threshold to conventional audiometric measures. The threshold values ranged from -7 to +7 dB signal-to-noise ratio for the 97 ears investigated. Reliability, expressed as standard deviation for repeated measurements, deteriorated from 0.7 to 1.1 dB as the threshold deteriorated. Learning effect between the first and the second threshold increased from 0 to 1 dB as the threshold deteriorated. No conventional audiometric test showed a high correlation to this threshold measure. The discrimination of the sentences without noise as well as the self-rated speech recognition in noise were also investigated.

Audiometry, Pure-Tone↗
PubMed1984

Some aspects of methodology in speech audiometry.

The aim of this study was to provide more knowledge about the influence of various factors on the reliability of speech audiometric measurements. On the basis of these data, new material on speech has also been developed for measurements of the speech reception threshold in noise. In a theoretical and a clinical investigation it has been shown that the reliability of speech discrimination scores may be predicted by using the binomial distribution. The reliability mainly depends on the score obtained and on the length of the word list. Curves with confidence intervals as well as diagrams which indicate when two different discrimination results deviate significantly from each other are presented. On the whole, the reliability is surprisingly poor. The reliability of speech reception threshold (SRT) measurements was studied by computer simulations and clinical studies. The SRT results of "subjects" who had poor speech discrimination were unreliable and were greatly affected by the level at which the test started. Some new methods were also simulated, one of which (the 2x4-word method) was 8% faster and also somewhat more reliable in the clinical studies than the ordinary 10-word method. It was also less affected by the patient's speech discrimination. Several speech lists with exactly the same content of sound, but with new sentences, were obtained by editing a list of ten spoken Swedish sentences in a computer. A noise was synthesized from the speech material by the computer to obtain the exact same spectrum of the speech and the noise. This material was tested monaurally on normal-hearing subjects and hearing-impaired subjects. A very steep intelligibility curve was obtained in noise (25%/dB), which gave a standard deviation of only 0.44 dB at repeated threshold measurements in noise for the normal-hearing subjects when the learning effect was outbalanced. This figure increased to 1.1 dB for those with severely impaired hearing. The learning effect between the first and the second thresholds did not exceed 1 dB. The threshold values ranged from -8 to -5 dB signal-to-noise ratio for those with normal hearing and from -7 to +7 dB for those with impaired hearing. The new sentence and noise material developed is well suited for clinical measurements of the speech reception threshold in noise.

Adult↗
PubMed1979

Reliability in the determination of speech reception threshold (SRT).

Clinical measurements of the speech reception threshold (SRT) have been made in order to determine the parameter values of a psychometric function. SRT measurements were then simulated in a computer to obtain, among other things, the standard deviation of a number of measurements from one and the same "patient". "Patients" with poor speech discrimination resulted in bad reliability of the SRT and great sensitivity to the hearing level at which the test started. New methods are proposed here, which are both faster and less susceptible to influence from the patient's speech discrimination.

Aged↗