Speech Recognition Threshold In Noise Research Articles

Comparison of speech recognition threshold in noise using laboratory and clinical procedures

Determining threshold for speech in quiet and as a function of increasing noise levels has been used to quantify the effects of hearing loss in terms of attenuation and distortion [R. Plomp, J. Acoust. Soc. Am. 63, 533–549 (1978)]. The speech recognition threshold (SRT) in noise has also been found to be a sensitive measure of electroacoustic changes in amplification [D. Van Tasell and J. Yanz, J. Speech Hear. Res.30 , 377–386 (1987)]. The purpose of this study was to determine if there was close correspondence between the laboratory measure of SRT in noise and a shortened clinical version using the Van Tasell and Yanz monosyllabic, high-frequency words. The clinical procedure was based on the SRT method recommended by the American Speech, Language, and Hearing Association and involved two conditions, quiet and speech-shaped noise at a moderate intensity level. The derived values of attenuation and distortion were significantly correlated across the two procedures. [Research supported by NIDCD of NIH.]

Speech Recognition in Noise: Development of a Computerized Test and Preparation of Test Material

In adaptable, Finnish language, "speech in noise" test was developed using a personal computer equipped with a sound card. each of the 1000 test items stored as a separate digitized wave form file on the hard disk of a personal computer consisted of disyllabic words on one stereo track and synchronized speech noise on the other. Because only a few randomly selected words are presented in this test for SRTN (speech recognition threshold in noise or S/N ratio corresponding to 50% recognition) the selection and equalization of test material is considered to be crucial to the achievement of reproducible results in short time. Equalization of the test items (word + noise) in accordance with degree of difficulty, by adapting the noise signal to the properties of the corresponding word, and selection of 510 of the initial 1,000 recordings with the smallest SDs are described. The effect of this procedure on the test-retest reliability of testing SRTN is evaluated. Despite contrary expectations, the procedure appears to have no effect on the reliability of the speech recognition threshold in noise (SD from 1.5 to 1.7 dB).

Effect of time scale modification of speech on the speech recognition threshold in noise for elderly listeners.

The effect of time scale modification of speech on the speech recognition threshold in noise (SRTN) was investigated for a group of 44 elderly subjects, varying in age from 56 to 88 years with sloping mild-to-moderate sensorineural hearing losses. Subjects' pure-tone average thresholds at 500, 1,000 and 2,000 Hz (PTA1) ranged from 3 to 58 dB. The study confirms the well-known fact that speech recognition in noise deteriorates with increasing age. Furthermore, time-compressing speech results in an even greater influence of age on the SRTN. The apparent age effect on SRTN values referenced to SRTN in the control condition is mostly caused indirectly by the significant correlation between age and PTA1, although there was a slight tendency for age to have a greater independent effect on relative SRTN values when the amount of time compression increased. The percentage of explained variance in relative SRTN values by the subject variables in this study was limited, indicating that there are other factors not investigated in this study (e.g. cochlear mechanisms, short-term memory, feature extractors) that significantly influence the effect of time compression on SRTN.

Effects of an adaptive filter hearing aid on speech recognition in noise by hearing-impaired subjects.

In a digitally controlled adaptive filter, ongoing detection and spectral analysis of quasi steady state noise are performed, and analog filter parameters are adjusted to provide greatest attenuation in frequency regions where noise energy is greatest. Attenuation introduced by the filter affects both speech and noise signals in the attenuation region. Effects of a master hearing aid incorporating an adaptive filter chip were assessed by measuring aided speech recognition threshold in noise with and without the filter. Performance of four hearing-impaired subjects showed that filter effects were related both to the frequency spectrum of the noise and to the distribution of speech information by frequency. No improvement in speech recognition threshold was seen for broadband speech materials in broadband noise. Better performance was observed for low-frequency noise in combination with speech materials for which the important information was confined to high frequencies.