Mechanical Impedance of the Forehead and Mastoid

Measurements of the mechanical impedance presented to a driver tip by the human forehead and by the mastoid have been made over the frequency range from 60 to 10 000 cps, using a special direct‐recording force and acceleration measuring system. The effect of the static force coupling the driving tip to the head has been investigated. At high coupling forces, the mastoid and forehead present similar impedances; the difference between mastoid and forehead impedance is greater at light coupling force. Over a large part of the audio‐frequency range, the predominant characteristic of both head and mastoid impedance is a stiffness reactance with some damping. In the high‐frequency range, a small mass reactance parameter appears. The mass load due to the whole head influences the impedance only at the low‐frequency extreme of the measurement range.