Effects Of Presentation Level Research Articles

Effect of hearing aids on speech perception in noisy situations.

Hearing-impaired people often complain about poor speech intelligibility when they are in noisy surroundings. Several authors have published data suggesting that hearing aids add distortion to the signal and thus make speech less intelligible. Given the tendency of people to speak louder in competing noise, it means that some patients might understand better in such circumstances without an aid than with an aid. The present study investigated the effect of modern commercial hearing aids on the ability of patients to understand speech monaurally in noisy circumstances. The results in general showed speech to be equally understandable with and without an aid if the effects of presentation level (amplification) are excluded. The results, however, varied considerably between patients. Statistical analysis showed that the variance could be explained primarily by the degree of high-frequency loss and the slope of the audiogram. Patients with steep sloping audiograms understand better and patients with a conductive hearing loss component understand less in noisy circumstances with a hearing aid. Speech intelligibility in noisy situations did not correlate at all with the hearing loss averaged over the mid-frequencies (500, 1,000 and 2,000 Hz) but it did correlate with the high-frequency hearing loss (2,000 and 4,000 Hz) and the slope of the audiogram, indicating the importance of high-frequency emphasis in hearing aids.

An evaluation of the speech perception in noise test

The effects of presentation level and signal-to-babble ratio (S/B) on SPIN performance were investigated for eighty normal hearing listeners. Both intensity and S/B had a significant effect on scores. Performance improved at the more favourable S/B regardless of presentation level, and scores were better at the lower presentation level regardless of S/B. Possible clinical applications of the SPIN test are discussed.

Effect of presentation level on the SSW test with hearing-impaired adults

The effects of varying presentation level on the Staggered Spondaic Word (SSW) test scores of sensorineural hearing-impaired subjects were investigated. Subjects were 15 adults having cochlear hearing losses between 30 and 50 dB (re: PTA). Performance-intensity (PI) functions were generated using subjects SSW test scores. Each subject received all 40-SSW test items, but the PI functions were generated by presenting items numbered 1–10 at 20 dB SL (re: three frequency PTA); 11–20 at 30 dB SL; 21–30 at 40 dB SL; and 31–40 at 50 dB SL. These results for the hearing-impaired were compared to functions reported earlier for normal subjects [P. C. Doyle, thesis, University of California, Santa Barbara (1981)]. The PI functions were analyzed for “competing” versus “noncompeting” conditions, and differences between subjects' raw SSW scores and word discrimination scores as a function of presentation level. Practical and theoretical implications for the clinical presentation of the SSW test at the various intensity levels to hearing-impaired adults are discussed.