CHARACTERIZATION OF EXTERNAL EAR IMPULSE RESPONSES USING GOLAY CODES

This report explains the use of a complementary series, Golay codes, for probing the impulse resPonse of the external ear. The codes are used to measure both the resonance of the human ear canal, using a sealed sound-delivery system, and to measure the transfer function of the pinna, using a free-field source. With two series of 512 binary numbers, the improvement in signal-to-noise ratio over a single impulse approaches the theoretical value of 30.1 dB [10 log(2.512)]. This technique has many of the same properties as maximal-length sequences [M. R. Schroeder, J. Acoust. Soc. Am. 66, 497-500 (1979) J, but it has the added advantage that the sequence length is an integer power of two and is, therefore, particularly convenient to use with modem Fourier transform techniques.