THE RELATIONSHIP BETWEEN SOUND TRANSFER-FUNCTIONS AND HEARING LEVELS

The effects of individual differences in sound transfer function (STF) from free sound field to the tympanic membrane on hearing levels was studied in the right and left ears of 55 young male and 45 young femal e subjects. Furthermore, canal volumes and lengths have been recorded. STFs were measured in 1/3-octave bands using a miniature microphone a nd an attached probe. STF measurements were performed in the 0.5-16 kH z frequency range. Audiograms were registered with linear frequency sw eep from 0.25 to 8 kHz. Transfer function spectra and magnitudes as we ll as ear canal dimensions were compared to hearing levels. There was a significant relationship between the dimensions of the ear canal and hearing levels. Large, compared to small, ear canal volumes resulted in a shift of STFs towards lower frequencies. STF spectra and magnitud es had a significant effect on hearing levels. Subject with low-freque ncy-dominated STFs have higher hearing thresholds than subjects with l ower magnitude STFs.