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Biomedical subjects

R M Cox

Publications and source records attributed to R M Cox.

At least 55 records · Page 3Linked to original sources
PubMed1988

Use of the Connected Speech Test (CST) with hearing-impaired listeners.

Two studies were performed in which hearing-impaired subjects responded to the Connected Speech Test (CST). In experiment 1, 40 subjects, divided into four groups according to extent and configuration of hearing loss, responded to the CST version 1 (CSTv1). This version of the test consisted of 57 passages of connected speech: 48 test passages and 9 practice passages. It was developed on the basis of data for normal-hearing listeners. Performance of hearing-impaired listeners for the CSTv1 revealed that, although the passages were equal in average intelligibility for normal hearers, they were not equally intelligible for hearing-impaired persons. Based on results of data analyses, the 57 passages were reconstituted into 28 pairs of passages: 24 test pairs and 4 practice pairs. The pairs were equal in average intelligibility for both normal and hearing-impaired listeners. This form of the test was named the CST version 2 (CSTv2). In experiment 2, an additional 23 hearing-impaired subjects responded to the CSTv2. Critical differences and the slope of the signal to babble ratio (SBR) function were determined for the CSTv2 for hearing-impaired listeners. When two CSTv2 pairs were used per score, the 95% critical difference for hearing-impaired subjects was about 15.5 rationalized arcsine units (rau). The mean SBR function slope for hearing-impaired listeners was 8.5 rau/dB. Comparing the critical difference with the SBR function slope, it may be seen that, for hearing-impaired listeners, differences in intelligibility equivalent to a 2 dB change in SBR can be detected with CST scores based on mean performance across two passage pairs.

Adult↗
PubMed1988

Distribution of short-term rms levels in conversational speech.

For 30 male and 30 female talkers, distributions of short-term rms speech levels, relative to the corresponding long-term rms levels, were determined in each of eight 1/3-oct bands for six short-term measurement intervals. Consecutive, Hanning-windowed, 20-ms time records were combined to produce nominal measurement intervals ranging from 20 to 120 ms. For each measurement interval, mean distributions of short-term rms speech levels relative to long-term levels were very similar for male and female talkers, and intertalker differences were small, especially for short-term amplitudes above the median level. The distribution of short-term rms speech levels relative to long-term rms speech levels varied with measurement interval for the short-term measurements. The effects of measurement interval was least for the highest amplitude speech levels and increased as speech levels decreased. For short-term amplitudes above the median level, the effect of measurement interval was greater in higher frequency regions, whereas for short-term amplitudes below the median level, measurement interval had the greatest effect on the lower frequency bands. These data may facilitate comparisons among investigations using different measurement intervals. In addition, they have implications for amplification strategies.

Female↗
PubMed1987

Electroacoustic calibration for sound field warble tone thresholds.

Walker, Dillon, and Byrne (1984) suggested reference equivalent threshold sound pressure levels (RETSPLs) for warble tones with specific modulation parameter values audited from a test position at the critical distance in a semireverberant sound field. This study evaluated these RETSPLs in two typical audiometric rooms and with typically encountered FM tones. Thresholds were measured under earphones and in two sound fields for 6-11 normal hearers at six test frequencies. Results indicated that there was a small but statistically significant difference between earphone and sound field thresholds in 4 of 24 comparisons. However, in both sound fields, 99% of the sound field thresholds were within 10 dB of the earphone thresholds. It is concluded that these RETSPLs are appropriate for electroacoustic calibration of sound field warble tones similar to those used in this study.

Acoustic Stimulation↗
PubMed1987

Development of the Connected Speech Test (CST).

This paper describes the first phase in the development of the Connected Speech Test (CST). This test of intelligibility of everyday speech has been developed primarily for use as a criterion measure in investigations of hearing aid benefit. The test consists of 48 passages of conversationally produced connected speech. Each passage contains 25 key words for scoring. All passages are of equal intelligibility for the average normal hearer. Key words vary in intelligibility within a passage but span the same intelligibility range in all passages. Several passages are administered, and the results averaged, to yield a single intelligibility score. For pairs of scores, each based on mean performance across 4 randomly-chosen passages, the 95% critical difference is estimated to be about 14 rationalized arcsine units (rau). The performance-intensity function for the CST has a slope of 12 rau/dB signal-to-babble ratio. Investigations of the test are continuing with hearing-impaired listeners.

Auditory Threshold↗
PubMed1987

Intelligibility of average talkers in typical listening environments.

Intelligibility of conversationally produced speech for normal hearing listeners was studied for three male and three female talkers. Four typical listening environments were used. These simulated a quiet living room, a classroom, and social events in two settings with different reverberation characteristics. For each talker, overall intelligibility and intelligibility for vowels, consonant voicing, consonant continuance, and consonant place were quantified using the speech pattern contrast (SPAC) test. Results indicated that significant intelligibility differences are observed among normal talkers even in listening environments that permit essentially full intelligibility for everyday conversations. On the whole, talkers maintained their relative intelligibility across the four environments, although there was one exception which suggested that some voices may be particularly susceptible to degradation due to reverberation. Consonant place was the most poorly perceived feature, followed by continuance, voicing, and vowel intelligibility. However, there were numerous significant interactions between talkers and speech features, indicating that a talker of average overall intelligibility may produce certain speech features with intelligibility that is considerably higher or lower than average. Neither long-term rms speech spectrum nor articulation rate was found to be an adequate single criterion for selecting a talker of average intelligibility. Ultimately, an average talker was chosen on the basis of four speech contrasts: initial consonant place, and final consonant place, voicing, and continuance.

Adult↗
PubMed1986

Comparison of in-the-ear and over-the-ear hearing aid fittings.

A custom in-the-ear (ITE) hearing aid fitting was compared to two over-the-ear (OTE) hearing aid fittings for each of 9 subjects with mild to moderately severe hearing losses. Speech intelligibility via the three instruments was compared using the Speech Intelligibility Rating (SIR) test. The relationship between functional gain and coupler gain was compared for the ITE and the higher rated OTE instruments. The difference in input received at the microphone locations of the two types of hearing aids was measured for 10 different subjects and compared to the functional gain data. It was concluded that (a) for persons with mild to moderately severe hearing losses, appropriately adjusted custom ITE fittings typically yield speech intelligibility that is equal to the better OTE fitting identified in a comparative evaluation; and (b) gain prescriptions for ITE hearing aids should be adjusted to account for the high-frequency emphasis associated with in-the-concha microphone placement.

Acoustics↗
PubMed1986

Damping the hearing aid frequency response: effects on speech clarity and preferred listening level.

Damped hearing aid frequency responses were compared with undamped responses to determine the effect of response smoothing on speech clarity and on gain received when the hearing aid was adjusted to the preferred listening level (PLL). Damping elements were located in the hearing aid's earhook. Three commercially available hearing aids, two bandwidths, and two speech input levels were evaluated in a completely crossed experimental design. Data were collected using a paired comparison method and 10 hearing-impaired subjects. Results indicated that the undamped frequency responses were judged to produce more clear, pleasant, natural sounding speech than the damped responses (p = .09). Although significant midfrequency peak reduction was achieved through earhook damping, the effects on gain at PLL were negligible.

Acoustics↗
PubMed1986

Reference equivalent threshold levels for pure tones and 1/3-oct noise bands: insert earphone and TDH-49 earphone.

Reference equivalent threshold sound pressure levels (RETSPLs) were determined for 20 subjects for pure tones and 1/3-oct noise bands. Two transducers were used: a Telephonics TDH-49 earphone mounted in an MX-41/AR cushion, and a Danavox SMW insert earphone coupled to an "HA-2" earmold. RETSPLs for pure tones transduced by the TDH-49 earphone were very similar to those published previously. For each transducer, RETSPLs for 1/3-oct noise bands were essentially identical to the RETSPLs for pure tones near the center of each band. Applications for threshold testing using the insert earphone and/or 1/3-oct noise bands are discussed.

Adult↗
PubMed1986

NBS-9A coupler-to-eardrum transformation: TDH-39 and TDH-49 earphones.

A transformation was derived to convert sound-pressure levels referenced to an NBS-9A coupler to corresponding eardrum sound-pressure levels. It was found that the same transformation may be used for male and female adults and for both TDH-39 and TDH-49 earphones in MX-41/AR supra-aural cushions. It was determined that from 250-2000 Hz the transformation provides an eardrum sound-pressure level estimate that is within 6 dB of the actual eardrum level for 95% of individuals. However, in the 4000-6300-Hz range, the accuracy deteriorates to +/- 12 dB of actual eardrum level for 95% of individuals.

Audiometry↗
PubMed1984

Relationship between two measures of aided binaural advantage.

The relationship between aided binaural squelch measured using a conventional paradigm and binaural squelch inferred from the ability to detect an intelligibility difference between binaural and pseudobinaural stimuli (presumably utilizing interaural time and intensity cues) was investigated. The conventional measures of aided binaural squelch included the NU-6 monosyllables and the high-predictability sentences from the revised SPIN test. For each measure, binaural squelch was derived by comparing the binaural intelligibility of speech-in-babble with corresponding monaural scores. Subjects were also asked to select the more intelligible hearing-aid-processed speech sample when presented with a paired-comparison task in which each pair consisted of a binaural and a pseudobinaural stimulus. Ability to choose the binaural stimulus as most intelligible was considered to be evidence of binaural squelch ability. Although the hearing-impaired subjects demonstrated typical binaural squelch for the conventional speech tests, they were usually unable to distinguish between the binaural/pseudobinaural pairs. These results suggest that (a) binaural squelch measured using conventional procedures does not necessarily quantify the listener's ability to profit from interaural differences, and (b) many hearing-impaired individuals may be unable to utilize interaural differences to enhance speech intelligibility in noise.

Acoustics↗
PubMed1984

Intelligibility ratings of continuous discourse: application to hearing aid selection.

Twelve normal-hearing subjects rated the intelligibility of 35-s, hearing-aid-processed continuous discourse (CD) passages. Three talkers (two male, one female), four hearing aids, and two signal-to-babble (S/B) ratios were used in a completely crossed design. Research questions concerned: (1) ability of listeners to rate intelligibility, (2) sensitivity of hearing aid rankings were based on intelligibility ratings for three CD passages per instrument, and (3) dependence of hearing aid rankings on (a) S/B ratio, and (b) talker characteristics. Results were: (1) listeners were able to rate intelligibility, (2) rankings based on intelligibility ratings of three CD passages per hearing aid were capable of identifying two superior instruments within a group of four hearing aids that were similar in frequency/gain function, (3) listening in a more difficult S/B ratio substantially decreased the sensitivity of the hearing aid rankings for the female talker but had only minor effects on the rankings for the male talkers, and (4) hearing aid intelligibility rankings were found to be different for different talkers. Applications to hearing aid selection are discussed.

Adult↗
PubMed1975

Room temperature stability of drug products labeled for refrigerated storage.

The stability at room temperature of many pharmaceutical products labeled for storage under refrigeration is presented. The data were obtained through a survey of manufacturers. It is observed that many drug products labeled for refrigerated storage are stable at room temperature for extended periods.

Drug Stability↗