Velocity of propagation of bone-conducted sound in a human head

A psychophysical cancellation method after Zwislocki [J. Acoust. Soc. Am. 25, 752-759 (1953)] was used to measure the propagation velocity of bone-conducted sound across the head of an observer. The result, 330 m/s, compares quite well with Zwislocki's earlier value of 260 m/s and Franke's of 300 m/s. Since in all three experiments the velocity was frequency-independent at f greater than 2000. Hz, it is suggested that vibratory energy travels along the flat bones of the cranial vault in the form of plate waves and as distortional waves through its base. [As defined by Cremer and Heckl, Körperschall (Springer, Berlin, 1967), plate waves are but a simpler form of distortional waves.] Quantitatively, the present result appears quite reasonable in the light of the material constants involved and by comparison with other materials.