Electro-acoustic performance of the new bone vibrator Radioear B81: a comparison with the conventional Radioear B71.

OBJECTIVE

The objective is to evaluate the electro-acoustic performance of a new audiometric bone vibrator, the B81 from Radioear Corporation, USA. Comparison will be made with the widely used B71 which has well-known limitations at low frequencies.

DESIGN

The B81 is based on the balanced electromagnetic separation transducer (BEST) principle where static forces are counterbalanced so that nonlinear distortion forces are reduced and maximum hearing levels can be increased.

STUDY SAMPLE

Maximum hearing level, total harmonic distortion (THD), frequency response, and electrical impedance were measured for six devices of each bone vibrator type on an artificial mastoid.

RESULTS

It was found that B81 reaches 10.7-22.0 dB higher maximum (@ THD = 6% or Vin = 6 VRMS) hearing levels than B71 for frequencies below 1500 Hz, and had significantly lower THD up to 1000 Hz. There was no statistically significant difference between their frequency response, except a deviation at the mid frequencies (α = 0.01) where B81 was more efficient and the electrical impedances were practically the same.

CONCLUSIONS

In general, B81 had an improved electro-acoustic performance compared to B71 and is compatible with same audiometers. In particular, B81 allows for sensorineural hearing loss to be measured at considerably higher hearing levels than with B71 below 1500 Hz.