Investigation Of Chinese Mandarin Intelligibility And Sound Location For The Elderly

Due to hearing loss,the elderly often cannot hear or understand the words of others,especially in the environment with noise and reverberation.Hearing loss has a great impact on their lives.In the thesis,three rooms with different reverberation time and different functions were selected as experimental sites in a nursing home in Guangzhou,subjective listening evaluation about Chinese Mandarin was carried out by 12 elderly participants and 8 young adults with normal hearing under different signal-to-noise ratio and noise azimuth angles.The results showed that the Chinese intelligibility improved with the increase of signal-to-noise ratio,the spatial separation of speech and noise and the decrease of reverberation time for the elderly participants.The improvements of intelligibility scores for spatial separation azimuth between speech and noise from 0 to 45 degrees were more than those from 45 to 90 degrees in all three rooms for the elderly.When the signal-to-noise ratio increased equally or the speech signal source and noise source were separated spatially,the increase of the speech intelligibility score under low signal-to-noise ratio was more than that under high signal-to-noise ratio for the elderly.There was a great difference in the Chinese intelligibility scores of hearing impairment elderly and normal hearing elderly under low signal-to-noise ratio conditions and the difference decreased with the increase of signal-to-noise ratio.The difference in the Chinese intelligibility scores between hearing impairment participants and normal hearing participants also became smaller when the target speech and noise was spatially separated.The comparison between the results of the elderly participants and young adults showed,regardless of hearing loss or not for the elderly,they had worse speech intelligibility than young adults with normal hearing in the same conditions.When the speech signal source and noise source were separated spatially,the increase of the speech intelligibility score for the elderly was more than that for the young adults.In order to verify the applicability of the test results,two rooms in another nursing home were selected for testing.The results showed that there was no significant difference in the speech intelligibility scores for the elderly subjects in the two nursing homes when the hearing level of the selected elderly participants was similar and the reverberation time of the selected rooms was relatively close.Considering that it was troublesome to go to the site for actual testing for the elderly.In the thesis,different signal-to-noise ratio and different noise azimuth angles were adopted in the two rooms with different reverberation time.The listening evaluation for the elderly over 60 years old was carried out in the mode of loudspeaker reproduction and headphone reproduction after using artificial head recorded that obtain the Chinese speech intelligibility scores to explore the effect of reproduction on the evaluation of Chinese intelligibility score for the elderly,the results were compared with those obtained by young adults with normal hearing.The results showed that Chinese speech intelligibility scores obtained in the loudspeaker reproduction mode were slightly higher than those obtained in the headphone reproduction mode.The scores difference between two reproduction modes for the elderly was slightly higher than that for the young adults.However,there was no significant difference in speech intelligibility between loudspeaker reproduction and headphone reproduction for the elderly.After the Chinese speech intelligibility evaluation was completed,the experiment of locating noise sound source was also carried out for the participants in the thesis.The tests in the two nursing homes showed,among the three rooms,the results of locating noise source in the room with shorter reverberation time were better than those with longer reverberation time.The elderly participants were less sensitive to the azimuth of lateral noise source than to the azimuth of forward noise source.The experiment on the effect of two reproduction modes on sound source location showed that there was a great difference in the results of sound source location between the two reproduction modes for the elderly participants.The results of sound source location in the headphone reproduction mode were worse than those in the loudspeaker reproduction mode for the elderly participants and young participants.The ability of locating sound source for the elderly participants decreased more severely than that for young participants in the headphone reproduction.It should be pointed out that these results were obtained from the experiment at limited noise source azimuths.The further study is to increase the number of noise azimuth angles and the number of participants.