Intelligibility of the Frequency-Shifted Words heard by the Hearing Impaired Persons with Hearing Aids

Abstract

Effectiveness in speech reception of the frequency-shifted words was evaluated in the elderly persons with sensorineural hearing impairment and using hearing aids. The subjects were 11 persons (including 2 females) with the mean hearing levels between 46dBHL and 83dB HL. The word intelligibility was measured under environmental noise level of 45-50dB (A) and speech sound level of 70dB (A) at the listening position 2 meters apart from a loud speaker. Two sets of 50 words, one was of ordinal pitch range and another was of very high pitch range, uttered by female narrators, were used for this evaluation. Each word set was modified it's pitch frequency and spectral envelop simultaneously up and down, that is frequency-shifted, by every one fourth octave. All subjects heard all modified word sets. Consequently, it was considered that the frequency compression for high voice was effective in improvement of word intelligibility and there would exist the frequency range where all subjects felt easy to listen. However, it was suggested that the frequency shift of wide range would cause perceptible voice character changes. Further, it was suggested that the pitch frequency of speech materials for auditory test would possibly influence to the test results.