C . COMPARISONS BETWEEN DIFFERENT MEASUREMENTS OF THE AUDITORY , VISUAL , AND AUDIOVISUAL SPEECH PERCEPTION ABILITY OF HEARING IMPAIRED SUBJECTS ; SOME PRELIMINARY RESULTS

The aim of this study is to give a preliminary base for a communication profile, which could be used in rehabilitative work when designing an individual training programme. A comparison is made between hearing impaired persons' results from auditory measurements (PTA, speech discrimination in quiet and noise) and their results from different speechreading tests, both visual and audiovisual. The answers on a questionnaire, Nearing Performance Inventory (HPI), in which the hard of hearing person evaluates his difficulties in different situations are correlated with the results from tests, as well as with the duration of loss. A new method to measure audiovisual speech perception in noise is described. Subjects were 13 prelingually hearing impaired persons. There was a significant correlation (p<.05) between the results on the five tests measuring speechreading ability and the duration of loss. One test of speech perception in noise correlated (p<.05) with HPI-answers concerning auditory speech perception, the reaction to auditory failure, and the hearing impaired person's experiences in his social situation. The results from the new audiovisual test did not give any significant correlation with the HPI-measures. Introduction "Any restriction or lack of ability to perceive sounds in either quiet or noisy backgrounds within the range considered as normal," is the definition of hearing disability made by World Health Organization (WHO) 1980. For a person with a hearing disability, it is important to get the most effective support system to the distorted auditory system. For many hard of hearing persons, a well fitted hearing aid will be a satisfactory solution, even if they will have more or less pronounced difficulties in the perception of speech in noise. The evaluating procedure used at the audiologic clinic then gives for most of the hearing impaired persons enough information to fit a hearing aid. The opthnum selection of gain, frequency response, use of amplitude compression, etc of the hearing aid is, however, still under discussion. There are some hard of hearing persons, who do not get enough support by the hearing aid, especially in noise (Plomp, 1978). They need a rehabilitation period to get used to the hearing aid and to learn to make use of other cues important for the speech perception process as speechreading and the possibility to combine auditory and visual information. When designing a rehabilitation programme for a hearing impaired, it would be very useful, if he could go through a battery of tests that measure different aspects of his communication difficulties. The test results then form a communication profile. Based on this profile, the hearing impaired person can be placed into an individualised training programme. The ultimate goal of our work is the design of such a communication profile. At the Hearing Institute in Uppsala, this strategy has been used for some years. The test battery consists of a number of standard audiological tests as well as speecbreadhg tests and questionnaires. The aim of the present study is to get a preliminary evaluation of the different tests used and some results from a newly developed method of measuring auditory and audiovisual speech-perception ability in noise. Although this last test situation is the situation that corresponds best with a person's real-life situation, there is at present no standard procedure for a test of this type. There is, however, a growing interest for this test procedure and a number of different tests have beem wied (Middlewerd & Plomp, 1987; Hawkins, Montgomery, Meuller, & Sedge, 1988). Subjects In the study, 13 hearing impaired persons, ten women and three men, participated. They were enrolled in a rehabilitation programme at the Hearing Institute in Uppsala. All had a sensorineural hearing impairment. They wore hearing aids and communicated orally, but they all expressed problems in many communication situations. The mean age was 41 years, range 21-70. The mean hearing loss (500, 1 000,2 000 Hz) was 64 dB, with the range 33-93 dB. They were tested with the below described test-battery at the onset of the rehabilitation course. Description of tests In the following, the different tests administered are described. For each test, the designation used in the table and the correlation matrix is given within parentheses. The tests are divided into four subgroups: A. Auditory tests to get information concerning the impaired auditory system. The auditory tests used were i) Pure Tone Audiometry (PTA), and ii) Speech Discrimination (Disc) measured by standard Swedish phonetically balanced (PB) word lists presented in quiet over headphones. Results are given for the hearing aided ear and, if the subject uses two hearing aids, for the best ear. iii) Speech Discrimination in noise (BH SIN) measured by Hagerman's test (Hageman, 1984). This test consists of fivewords sentences with the construction: fust name, verb, number, adjective, and noun. A sentence is constructed based on a choice between ten alternatives in each position. The test is presented in a speech-shaped noise and the signal-to-noise-ratio is established where 50% of the words in the sentences are correctly identified. The measurement was made with the fitted hearing aid in a free field. iv) In the last test on this level, the signal-to-noise-ratio was established, at which the subject estimated that he could just urtderstand continuous discourse (Subj.SIN;aud), which is a method based on methods described by Egan (1948) and Hawkins, & al. (1988) . A short story was recorded on videotape. The subject was first asked to adjust the level of the speech to a comfortable level in quiet without visual information. Noise was then added to the speech signal, and the subject was asked to adjust the noise level so that he could just follow the speaker. He was also told that the tape could be stopped, and he had to answer some questions about the content of the story. The adjustment of the noise level was made eight times and the median value of the adjusted signal-to-noise-ratios was calculated. The signal was presented over headphones (TDH39) on the hearing aided ear. The noise was pink-shaped.