Abstract
The tranquil solution for the hearing impaired subjects to get rid of the impairment is to wear the appropriate hearing aid to increase the hearing level and clarity of the perceived speech. Though the present day hearing aids are inbuilt with a suitable noise removing algorithm to get a clear speech signal, the satisfaction among the users is low. The satisfaction of the hearing aid users will be enhanced only with the fixation of appropriate Real Ear Insertion Gain (REIG) values for different frequency bands of the perceived speech signal. Various prescriptive procedures were developed so far in prescribing these values. But, the strenuous task for the audiologists is in selecting the best procedure and to suggest required modifications. The present work focuses this problem faced by the audiologists by analyzing the various technical snags and arrived with suitable solutions. In the present work, an expert system was developed to predict gain values without the need of the prescriptive procedures and reduced the trial and error time of the audiologists. A gain suggestion database of the satisfied subjects was developed, and later it was used by the correlation algorithm in the gain prediction process. The successful gain suggestions of the most correlated subject for different frequencies in the database are recommended for the new subject. The developed expert system was validated by performing hearing aid trials with 256 hearing impaired subjects and 93.7% of them received satisfaction. The successful gain suggestions made by the expert system are stored continuously to strengthen the database, so as to recommend the most appropriate gain values for the new subject.
Highlights
The hearing capability of an individual is assessed by performing pure tone and speech audiometric test
The important parameters used in the correlation algorithm are minimum threshold of hearing in dBHL for a particular octave frequency, Pure Tone Average (PTA) in dBHL which is an average of minimum threshold of hearing measured at three frequencies 500Hz, 1000Hz and 2000Hz, Sound input level in dBSPL for the hearing aid, and age of the subject
The successful gain suggestions of the correlated subject for three different sound input levels 40dBSPL, 60dBSPL and 80dBSPL are recommended to the new subject
Summary
The hearing capability of an individual is assessed by performing pure tone and speech audiometric test. Hearing aid trials were made to the impaired subjects fitted with gain values recommended by different successful prescriptive procedures. Based on the test conducted with population under study and with the SDS value calculated, it was found that, the procedures based on speech intelligibility from NAL acoustic laboratories NAL-R, NAL-NL1 and NAL-NL2 gave better satisfaction among all the prescriptive procedures [11 - 14]. The aim of the present work is to analyze the standards and parameters used in the various linear and nonlinear prescriptive procedures, by performing proper audiological investigations with the hearing impaired subjects, so as to develop an expert system to predict appropriate gain values for digital hearing aid. Since the gain values suggested to the new subject are from the satisfied gain suggestion database, the success rate of the expert system in predicting gain suggestions improved
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