Effect of Computer-Assisted Speech Training on Speech Recognition and Subjective Benefits for Hearing Aid Users With Severe to Profound Prelingual Hearing Loss

Introduction Sensorineural hearing loss (SNHL) is a disability affecting people worldwide, and the prevalence is expected to increase due to prolonged life expectancy. SNHL has a significant negative impact on the quality of life, especially in prelingually deafened children. Except for certain diseases such as sudden deafness or endolymphatic hydrops, which may be treated or alleviated by medication or surgery, most patients with SNHL have to wear hearing aids or undergo cochlear implantation to regain hearing. However, for many individuals these measures do not satisfactorily resolve communication problems, because hearing is only the first step in a series of events leading to communication. Between hearing and communication lie the important skills of listening and comprehension, and to achieve successful communication it has been suggested that patients receiving amplification should be offered some type of audiological rehabilitation. It has been reported that older subjects do not spontaneously acclimatize to wearing a hearing aid, or that the effects are either small or nonexistent, which emphasizes the importance of rehabilitation after wearing a hearing aid. Unfortunately, not everyone with SNHL in Taiwan receives this kind of rehabilitation. The reasons for this may be: (a) methods of rehabilitation are not familiar to all clinicians or speech pathologists; (b) there is a shortage of clinicians or speech pathologists to provide such time-consuming rehabilitation; (c) hearing impaired patients may be unable to afford or are unwilling to dedicate time to rehabilitation; and (d) it is difficult to measure the improvements provided by rehabilitation.

Recently, rehabilitative training procedures have been garnering interest due to technological advances enabling a hearing aid user to perform the procedures while at home using a personal computer. Burk et al trained young normal-hearing and older hearing-impaired listeners with digitally recorded training materials using a computer. The results showed that older hearing-impaired listeners were able to significantly improve their word-recognition abilities through training with one talker, and to some degree achieve the same level as young normal-hearing listeners. In addition, the improved performance was maintained across talkers and across time.

The computer-aided speechreading training (CAST) system was developed to simulate a face-to-face training intervention and was designed to be one component of a comprehensive aural rehabilitation program for preretirement adults with acquired mild-to-moderate hearing loss. The aim of the training was to enhance speechreading skills to complement auditory speech perception. Throughout the training, the learner views a monitor that shows either a computer-generated screen or a videotaped recording of the teacher. CAST was designed to be used by a clinician to extend rather than to replace existing rehabilitative techniques.

Computer-based training has also been applied to the rehabilitation of cochlear implant users. Before the development of computer-based training, some studies assessed the effects of limited training on the speech-recognition skills of poorer-performing cochlear implant users. Busby et al conducted ten 1-hour speech perception and production training sessions, and the results demonstrated minimal changes in perceptual abilities in three cochlear implant users. Dawson and Clark conducted one 50-minute training session per week for 10 weeks, and four of five subjects showed some measure of improvement. The limited success of these attempts to improve the speech-recognition abilities of cochlear implant users was thought to be due to an inadequate amount of training. More intensive training of cochlear implant users was predicted to be effective, because in normal hearing populations training has been shown to successfully improve speech segment discrimination and identification, and recognition on spectrally shifted speech. Fu et al reported encouraging results in the rehabilitation of cochlear implant users using a computer-assisted speech training system which they also called CAST, although this was different to the CAST system of Pichora-Fuller and Benguerel. The CAST system of Fu et al, developed at the House Ear Institute, contains a large database of training materials and can be installed on personal computers, and so with minimal facilities and skills, cochlear implant users can conduct the training at home, and clinicians or speech pathologists can monitor the subject's test score and training progress. The results demonstrated that after moderate amounts of training (1 hour per day, 5 days per week), all 10 postlingually deafened adult cochlear implant users in the study had significant improvements in vowel and consonant-recognition scores. Wu et al applied the CAST system to 10 Mandarin-speaking children (three hearing aid users and seven cochlear implant users). After training for half an hour a day, 5 days a week, for a period of 10 weeks, the subjects showed significant improvements in vowel, consonant and Chinese tone performance. This improved performance was largely retained for 2 months after the training had been completed. Stacey and Summerfield also used computer-based auditory training to improve the perception of noise. The results confirmed that the training helped to overcome the effects of spectral distortions in speech, and the training materials were most effective when several talkers were included.

Based on these previous studies, cochlear implant users can improve their speech recognition ability after training with a CAST system. If this system is also effective for hearing aid users, and especially prelingually deafened patients, the CAST system will have a substantially positive impact, as there are many more hearing aid users than cochlear implant users.