Biomedical subjects

R Plomp

Publications and source records attributed to R Plomp.

At least 37 records · Page 2Linked to original sources

PubMed1990

Auditive and cognitive factors in speech perception by elderly listeners.

A key issue in research on speech perception in the elderly is whether the difficulties in understanding speech are caused by auditive and/or cognitive factors. Resolving this issue is not only scientific interest but has many practical, i.e. diagnostic and rehabilitative, implications as well. We developed a test battery comprising auditive (sensitivity, frequency selectivity and temporal resolution), cognitive (memory performance, processing speed and intellectual abilities), and speech perception tests (at the phoneme, spondee and sentence level). This test battery was administered to 72 elderly subjects (aged 60 to 93 years). The results show that the deterioration of speech perception in the elderly consists of two statistically independent components (a) a large component mainly representing the progressive high-frequency hearing loss with age which accounts for approximately two-thirds of the systematic variance of the tests of speech perception, and (b) a smaller component (accounting for one-third of the systematic variance of the speech perception tests) mainly representing a general performance decrement due to reduced mental efficiency, which is indicated by a general slowing of performance and a reduced memory capacity. Although both components are correlated with age, it was found that the balance between auditive and cognitive contributions to speech perception performance did not change with age.

Aged↗

PubMed1990

A clinical test for the assessment of binaural speech perception in noise.

The present paper describes a clinical test for the assessment of speech perception in noise. The test was designed to separate the effects of several relevant monaural and binaural cues. Results show that the performance of individual hearing-impaired listeners deviates significantly from normal for at least 2 of the following aspects: (1) perception of speech in steady-state noise; (2) relative binaural advantage due to directional cues; (3) relative advantage due to masker fluctuations. In contrast, both the hearing loss for reverberated speech and the relative binaural advantage due to interaural signal decorrelation, caused by reverberation, were essentially normal for almost all hearing impaired.

Adult↗

PubMed1990

Difficulties with speech intelligibility in noise in spite of a normal pure-tone audiogram.

A group of 15 patients with complaints of having difficulties in understanding speech, especially in noisy surroundings in spite of (nearly) normal pure-tone audiograms, was subjected to a battery of speech-audiometric tests. The results showed that these subjects had a statistically significantly higher speech reception threshold (SRT) for sentences in noise than a reference group of 10 normal-hearing subjects. This difference was most clear for a fluctuating masking noise. In conditions with much reverberation, the patients also proved to be handicapped more than the control group. Binaural hearing gain was equal for both groups. The pathogenesis of the speech-hearing loss is not known, but assessment of the SRT in noise proves to be a valuable asset in objectifying these patients' complaints.

Adult↗

PubMed1990

Considerations on adaptive gain and frequency response in hearing aids.

Most sensorineurally hearing-impaired listeners need a better signal-to-noise ratio for speech reception than normal-hearing listeners do. This aspect of hearing loss is probably related to deterioration of the signal-analysing power of the ear. In an impaired ear, noise in one frequency region may have considerable masking effects in other frequency regions. To prevent the hearing-impaired listener from excessive masking, we need an adaptive hearing aid that selectively amplifies only those frequency bands with a signal quality that can contribute to intelligibility. It suffices to present signals in other frequency regions at a just-audible level. A signal-processing scheme is proposed that meets these requirements. The audiological reasoning for the spectral characteristics of such a hearing aid is illustrated with the Articulation Theory. The temporal characteristics required for adaptation to changes in the acoustic environment are discussed in terms of the Modulation Transfer Function. It is shown that amplitude compression with short time constants seriously reduces the quality of speech transmission as expressed in the Speech Transmission Index.

Hearing Aids↗

PubMed1990

Speech-reception threshold in noise for hearing-impaired listeners in conditions with a varying amplitude-frequency response.

In a study on the effects of a frequency-dependent automatic gain control in hearing-aids, two experiments were carried out with hearing-impaired listeners. In the first experiment, the effect of varying the amplitude-frequency response on the speech-reception threshold (SRT) of sentences presented in noise was studied. The noise had the same spectrum as the long-term average spectrum of the sentences. Results suggest that the amplitude-frequency response may vary within a range from, roughly, -3 to +10 dB/oct relative to the bisector of the dynamic range, without giving an increase in SRT larger than 2 dB. In the second experiment, the effect on masked SRT of adjusting the amplitude-frequency response to situations of seriously interfering low-frequency noise was studied. Again, the noise had a spectrum identical with the long-term average spectrum of the sentences, but this time the noise level in one octave band was increased by 20 dB. Preliminary results indicate that a selective attenuation of the signal in the band containing the extra noise may give a decrease of masked SRT up to 4.5 dB.

Audiometry, Pure-Tone↗

PubMed1989

The effect of varying the amplitude-frequency response on the masked speech-reception threshold of sentences for hearing-impaired listeners.

In an evaluation of frequency-dependent automatic gain-control systems in hearing aids, the effect of varying the amplitude-frequency response on the speech-reception threshold (SRT) for sentences in noise is studied for 20 hearing-impaired listeners. The noise has a spectrum identical to the long-term average spectrum of the sentences. Speech and noise are shaped by the same amplitude-frequency response; their spectra are varied relative to the bisector of the individual's dynamic range. In four experimental conditions, the effect of a steady-state amplitude-frequency response is studied. Steepening the negative spectral slope of speech and noise appears to cause an increase of masked SRT, possibly due to increased effect of upward spread of masking. The effect of a single transition of the amplitude-frequency response between 10 and -10 dB/oct halfway through the sentence seems to be related to the effect for the fixed -10-dB/oct condition. Two transition times are tested. For a transition time of 0.25 s, the SRT is only a little higher than for 1 s. The results suggest that the amplitude-frequency response may be varied in time without having a detrimental effect on the masked SRT of sentences for hearing-impaired listeners as long as strongly negatively sloping spectra are avoided.

Adult↗

PubMed1989

Binaural speech intelligibility in noise for hearing-impaired listeners.

The effect of head-induced interaural time delay (ITD) and interaural level differences (ILD) on binaural speech intelligibility in noise was studied for listeners with symmetrical and asymmetrical sensorineural hearing losses. The material, recorded with a KEMAR manikin in an anechoic room, consisted of speech, presented from the front (0 degree), and noise, presented at azimuths of 0 degree, 30 degrees, and 90 degrees. Derived noise signals, containing either only ITD or only ILD, were generated using a computer. For both groups of subjects, speech-reception thresholds (SRT) for sentences in noise were determined as a function of: (1) noise azimuth, (2) binaural cue, and (3) an interaural difference in overall presentation level, simulating the effect of a monaural hearing acid. Comparison of the mean results with corresponding data obtained previously from normal-hearing listeners shows that the hearing impaired have a 2.5 dB higher SRT in noise when both speech and noise are presented from the front, and 2.6-5.1 dB less binaural gain when the noise azimuth is changed from 0 degree to 90 degrees. The gain due to ILD varies among the hearing-impaired listeners between 0 dB and normal values of 7 dB or more. It depends on the high-frequency hearing loss at the side presented with the most favorable signal-to-noise (S/N) ratio. The gain due to ITD is nearly normal for the symmetrically impaired (4.2 dB, compared with 4.7 dB for the normal hearing), but only 2.5 dB in the case of asymmetrical impairment. When ITD is introduced in noise already containing ILD, the resulting gain is 2-2.5 dB for all groups. The only marked effect of the interaural difference in overall presentation level is a reduction of the gain due to ILD when the level at the ear with the better S/N ratio is decreased. This implies that an optimal monaural hearing aid (with a moderate gain) will hardly interfere with unmasking through ITD, while it may increase the gain due to ILD by preventing or diminishing threshold effects.

Adolescent↗

PubMed1989

Auditive and cognitive factors in speech perception by elderly listeners. I: Development of test battery.

This study compares performance of 24 young normal-hearing (aged 18-28 years) and 24 elderly (aged 61-85 years) listeners on auditive (sensitivity, frequency selectivity, and temporal resolution), cognitive (memory performance, processing speed, and divided attention ability), and speech perception tests (at the phoneme, spondee, and sentence level). Its principal aim is to assess whether the tests selected yield meaningful results. The results obtained will be used to reduce the test battery in order to be manageable in a second study on a much larger number of elderly listeners. The relationships between the tests are explored by multivariate statistical methods. The results show that: (a) in young listeners, individual differences in speech perception performance are remarkably small resulting in low correlations between the tests, while in the elderly tests of phoneme, spondee, and sentence perception overlap considerably; (b) speech perception in the elderly seems to be largely determined by hearing loss at the higher frequencies, whereas the effects of other auditive and cognitive factors seem to be relatively small or absent; and (c) performance in the elderly is only partly correlated with age.

Acoustic Stimulation↗

PubMed1989

The effect of stapedectomy on speech intelligibility in noise.

Speech intelligibility in noise was tested pre- and postoperatively after 27 stapedectomy cases and 10 cases of reexploration after previous stapes surgery. We did not find a postoperative threshold shift (signal-to-noise ratio) for the intelligibility of sentences presented in noise. This finding corresponds well with the absence of postoperative high-frequency sensorineural loss in these patients. Using two types of prostheses we found a significant amelioration of speech intelligibility in quiet for the Schuknecht minihole prosthesis as compared to the House wire loop.

Adult↗

PubMed1988

Automatic phonetogram recording supplemented with acoustical voice-quality parameters.

A new method for automatic voice-quality registration is presented. The method is based on a technique called phonetography, which is the registration of the dynamic range of a voice as a function of fundamental frequency. In the new phonetogram-recording method fundamental frequency (Fo) and sound-pressure level (SPL) are automatically measured and represented in an XY-diagram. Three additional acoustical voice-quality parameters are measured simultaneously with Fo and SPL: (a) jitter in the Fo as a measure for roughness, (b) the SPL difference between the 0-1.5 kHz and the 1.5-5 kHz bands as a measure for sharpness, and (c) the vocal-noise level above 5 kHz as a measure for breathiness. With this method, the voice-quality parameter values, which may change substantially as a function of Fo and SPL, are pinned to a reference position in the patient's total vocal range. Seen as a reference tool, the phonetogram opens the possibility for a more meaningful comparison of voice-quality data. Some examples, demonstrating the dependence of the chosen quality parameters on Fo and SPL are given.

Humans↗

PubMed1988

The effect of head-induced interaural time and level differences on speech intelligibility in noise.

A study was made of the effect of interaural time delay (ITD) and acoustic headshadow on binaural speech intelligibility in noise. A free-field condition was simulated by presenting recordings, made with a KEMAR manikin in an anechoic room, through earphones. Recordings were made of speech, reproduced in front of the manikin, and of noise, emanating from seven angles in the azimuthal plane, ranging from 0 degree (frontal) to 180 degrees in steps of 30 degrees. From this noise, two signals were derived, one containing only ITD, the other containing only interaural level differences (ILD) due to headshadow. Using this material, speech reception thresholds (SRT) for sentences in noise were determined for a group of normal-hearing subjects. Results show that (1) for noise azimuths between 30 degrees and 150 degrees, the gain due to ITD lies between 3.9 and 5.1 dB, while the gain due to ILD ranges from 3.5 to 7.8 dB, and (2) ILD decreases the effectiveness of binaural unmasking due to ITD (on the average, the threshold shift drops from 4.6 to 2.6 dB). In a second experiment, also conducted with normal-hearing subjects, similar stimuli were used, but now presented monaurally or with an overall 20-dB attenuation in one channel, in order to simulate hearing loss. In addition, SRTs were determined for noise with fixed ITDs, for comparison with the results obtained with head-induced (frequency dependent) ITDs.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential Threshold↗

PubMed1988

The negative effect of amplitude compression in multichannel hearing aids in the light of the modulation-transfer function.

The article deals with the question of why multichannel amplitude compression appears to have a negative rather than a positive effect on speech intelligibility by hearing-impaired listeners. It is argued that the small time constants of amplitude compression diminish the temporal as well as the spectral contrasts in the speech signal. According to the modulation-transfer function concept, this results in reduced intelligibility scores. Experimental evidence is reviewed indicating that the following two arguments in favor of amplitude compression in case of sensorineural hearing loss are not valid: (1) to compensate for the effects of loudness recruitment and (2) to get weak consonants above threshold. The author concludes that, in multichannel hearing aids, automatic gain control with time constants of 0.25-0.5 s should be given preference to amplitude compression.

Adult↗

PubMed1988

The timbre of sung vowels.

The perception of timbre differences in a vowel sung by eight male and seven female singers has been investigated by means of two types of listening experiments: (1) using the paradigm of the comparison of similarity, and (2) using judgments on 21 semantic bipolar scales. Using INDSCAL analysis for the similarity-comparison data and MDPREF analysis for the semantic-scale judgments, vowel configurations in a multidimensional perceptual space were derived, as well as a space that showed the weighting of perceptual dimensions by individual listeners (INDSCAL). The interpretation of semantic scales was represented by directions in the perceptual space (MDPREF). The perceptual vowel configurations, either based on timbre similarities or semantic scales judgments, were comparable. Broadly, semantic scales clustered into the categories vocal technique, general evaluation, vibrato, clarity, and sharpness. These five clusters were not independent and could be described in two dimensions. Timbre differences could be predicted on the basis of differences in 1/3-oct spectra of the vowels. It showed up that only sharpness had a constant interpretation for the various stimulus sets and was roughly related to the slope of the spectrum. One experiment, using a song phrase, extended the results to a more general domain.

Acoustic Stimulation↗

PubMed1987

[Acoustic trauma].

Explore the source record for details and available documents.

Ear Protective Devices↗

PubMed1987

The effect of varying the slope of the amplitude-frequency response on the masked speech-reception threshold of sentences.

Within the framework of a study on the merits of a frequency-dependent automatic gain control in hearing aids, the effect of varying the slope of the amplitude-frequency response on the speech-reception threshold (SRT) for sentences in noise was studied for normal-hearing listeners. Speech and noise were both subjected to the same amplitude-frequency response. In the first experiment, the effect of a constant slope was investigated (20 listeners). Over a range of about -7 to +10 dB/oct, the SRT in noise remained constant. In the second experiment, a single change in the slope of the amplitude-frequency response was introduced halfway through the sentence. The effect of varying the transition time over a range down to 0.125 s appeared to be very small. In the third experiment, the slope varied continuously with range and variation frequency (0.25-2 Hz) as the parameters. The masked SRT increased gradually with variation frequency. The results indicate that the masked SRT for sentences is remarkably resistant to dynamic variations in the slope of the amplitude-frequency response.

Hearing Aids↗

PubMed1987

The effect of speechreading on the speech-reception threshold of sentences in noise.

The monaural speech-reception threshold of sentences in noise, here defined as the 50% correct-syllables threshold, was measured for a female speaker with and without speechreading via a video monitor. The additional visual information resulted in a 4.6-dB lower threshold for a group of 12 young subjects and in a 4.0-dB lower threshold for a group of 18 elderly subjects compared to auditory presentation alone.

Adult↗

PubMed1986

A signal-to-noise ratio model for the speech-reception threshold of the hearing impaired.

This paper reviews the results of a series of investigations inspired by a model of the speech-reception threshold (SRT) of hearing-impaired listeners. The model contains two parameters accounting for the SRT of normal-hearing listeners (SRT in quiet and signal-to-noise ratio corresponding to the threshold at high noise levels), two parameters describing the hearing loss (attenuation and threshold elevation in terms of signal-to-noise ratio), and three parameters describing the hearing aid (acoustic gain, threshold elevation expressed in signal-to-noise ratio, and equivalent internal noise level). Experimental data are reported for three different types of hearing impairment: presbycusis, hearing losses with a pathological origin, and noise-induced losses. The model gives an excellent description of the data. It demonstrates that for many hearing-impaired persons speech intelligibility at noise levels beyond 50 to 60 dB(A) is their main problem, whereas hearing aids are most effective below that noise level.

Auditory Threshold↗

PubMed1986

The sound level of the singer's formant in professional singing.

The relative sound level of the "singer's formant," measured in a 1/3-oct band with a center frequency of 2.5 kHz for males and of 3.16 kHz for females, has been investigated for 14 professional singers, nine different modes of singing, nine different vowels, variations in overall sound-pressure level, and fundamental frequencies ranging from 98 up to 880 Hz. Variation in the sound level of the singer's formant due to differences among male singers was small (4 dB), the factors vowels (16 dB) and fundamental frequency (9-14 dB) had an intermediate effect, while the largest variation was found for differences among female singers (24 dB), between modes of singing (vocal effort) (23 dB), and in overall sound-pressure level (more than 30 dB). In spite of this great potential variability, for each mode of singing the sound level of the singer's formant was remarkably constant up to F0 = 392 Hz, due to adaptation of vocal effort. This may be explained as the result of the perceptual demand of a constant voice quality. The definition of the singer's formant is discussed.

Female↗