Evaluation of the Interaural Attenuation for Pure Tone Audiometry in Korean

Abstract

Background and Objectives: The masking should be used in pure tone audiometry when the difference between the air-conduction threshold of the tested ear and the bone-conduction threshold of the non-tested ear is more than interaural attenuation (IA). But the standardized average value of IA in Korean has not been evaluated until now. The purpose of this study is to evaluate the interaural attenuation in Korean population. Subjects and Methods: Of the patients who visited our department from March, 2007 to August, 2009, 44 patients were selected who had unilateral severe sensorineural hearing loss or deafness and contralateral normal hearing. When the difference between air-conduction threshold with and without masking was more than 10 dB, the interaural attenuation at each frequency was obtained by subtracting the contralateral bone conduction from the air-conduction threshold without masking. Results: The interaural attenuations at each frequency were 45-75 dB (250 Hz), 50-75 dB (500 Hz), 40-75 dB (1 kHz), 45-85 dB (2 kHz), 50-90 dB (4 kHz). 77.2% of the subjects showed interaural attenuation of 55-65 dB at 250 Hz, and 80.9% in 50-60 dB at 500 Hz, 79.5% in 55-65 dB at 1 kHz, 83.4% in 45-60 dB at 2 kHz, and 76.4% in 50-65 dB at 4 kHz. Most of the patients were distributed 15-25 dB higher than the minimal interaural attenuation at 1 kHz. At 2 kHz and 4 kHz, most of the patients were distributed around 15 dB of the minimal interaural attenuation. Conclusions: These results can be used as reference values for masking of pure tone audiometry. But, further studies with large population should be done to get more precise results and contributing factors to IA values.