Acoustic radiation produced by B-71, B-72, and KH 70 bone vibrators

The amount of acoustic radiation produced by two samples of a Radioear B-71, B-72, and Pracitronic KH 70 bone vibrator was determined for 30 normal-hearing subjects at 4000 Hz. The mean amount of acoustic radiation was very similar for both samples of each vibrator type but significantly (p less than 0.05) different between the bone vibrator types. The mean amount of acoustic radiation averaged over both samples was 8.3 dB for the B-72, 4.3 dB for the B-71, and -0.3 dB for the KH 70. Individual subject data indicated that the B-72 produced excessive acoustic radiation (greater than 5 dB) for 80% of the subjects, the B-71 for 38% of the subjects, and the KH 70 for 8% of the subjects which could cause an invalid high-frequency air-bone gap. Precautions should be taken during bone conduction audiometry to eliminate the possibility of acoustic radiation produced by bone vibrators. A need for additional standards in this area is stressed.