Development of frequency specific word recognition test for Turkish

Speech perception is one of the most important communicational abilities of human being in daily life. Because of the fact that speech tests that are used for evaluation of hearing impairment supply invaluable information about speech perception performance, they are considered as a basic component of audiological test battery. Utilizing human voice as a test signal, these tests are not convenient for supplying frequency specific information about the processing capacity of auditory system. The aim of this study was to develop a frequency specific word recognition test for Turkish which would aid to obtain frequency specific information in terms of speech perception ability. For this purpose, materials of word lists composed during development of Dokuz Eylul Word Recognition Test were utilized. Monosyllabic meaningful words which were recorded by an adult as well as a kid speaker were band-pass filtered at various widths of frequency bands. The high cut-off frequency of the filter band was set to 250 Hz constant, while the lower cut-off frequencies were set to 4, 3, 2, 1.5, 1 kHz for the adult speaker recordings and 8, 6, 4, 3, 2 kHz for the kid speaker recordings. In this way, for every word recordings, five different filtered derivations narrowing with half octave band intervals were obtained. All derivations were tested on young-adult listeners with normal hearing. According to the results which were obtained from the participants, the slopes of alterations in the rate of intelligibility of words that resulted by narrowing of filter frequency band were determined. As a result of this study, intelligibility rates of words were declining with different slope rates as a function of the filter bandwidth and spectral content of each word. The words which had declining intelligibility rates with high slope in one of the frequency ranges of 0.25-1 kHz, 1-1,5 kHz, 1.5-2 kHz, 2-3 kHz, 3-4 kHz, 3-6 kHz and 4-6 kHz were ascertained as candidate for speech materials of frequency specific word recognition test.