An Artificial Mastoid for the Calibration of Bone Vibrators

The development and construction of an artificial mastoid are described. The initial design was based on mechanical impedance measurements of the human mastoid carried out at the National Physical Laboratory. The final model takes into account a review of these and other data, and is suitable for audiometric and hearing aid applications. The performance of the device, determined by its ability to compare correctly the sensitivity of different bone vibrators, is discussed by reference to a series of subjective tests. Methods of measuring and calculating the objective sensitivity are also given, together with some data on the time and temperature stability.