Study on effective improvement of mobile phone sound quality in a noise environment for the hearing-impaired

For the hearing-impaired population, quality of sound when listening to speech on mobile phone is often dissatisfactory. Even with a turning up the volume, they feel mobile speech unclear and desire the mobile sounds to be amplified as suited for the hearing characteristics. The purpose of this study was to estimate the appropriateness of NAL-NL1 fitting formula for the hearing-impaired mobile communication.

NAL-NL1 and a modified fitting formula (M-formula) were applied for sound amplification in consideration of individual hearing loss. Amplified speech material was presented for a word-recognition score (WRS) test in each subject. To simulate actual mobile phone sound, all speech material was filtered in 8 kHz low-pass filter and presented through a mobile phone to the subjects. Speech material was categorized into a speech-without-noise group and noisy speech group.

Amplified sound with NAL-NL1 formula had a slightly better WRS than amplified speech with M-formula in speech-without-noise environments. However, in the noisy speech group, M-formula showed better WRS than NAL-NL1.

For a good speech-perception in mobile phones, more high-frequency speech components need to be provided, especially for noisy environments. This study showed the possibility that specified fitting strategies may be applied for mobile phones to improve hearing in various environments, as with hearing aids.