Anesthesia during measurement of bone conduction KA450

The crosstalk attenuation from one ear to the other is a maximum of 5 to 10 dB when measuring with the bone conduction receiver, and it is therefore assumed for safety's sake that the signal can also be heard by the opposite ear without attenuation.

Therefore, it is always necessary to anesthetize the opposite ear during bone conduction measurements, and it must be performed at least at the volume of the test signal if the opposite ear is completely intact.

Deafening is performed if the bone conduction on one side deviates by 10 dB or more, or if there is a bone conduction-air conduction difference of 15 dB or more.

First, the bone receiver is placed on the mastoid. The air receiver is used for anesthesia as follows:

One air receiver capsule is placed on the ear to be deafened. The other air receiver capsule is placed on the side of the test ear in the temple area so that the auditory canal remains open.

As with the air duct measurement, the masking signal is usually a narrow band noise (NBN = Narrow Band Noise), the volume of which can be adjusted using the level control (42, 47).

Depending on the hearing loss of the ear to be masked, a correspondingly louder masking sound should be selected compared to the test signal.

The following values can be used as a rule of thumb for anaesthetization with bone conduction:

70 dB for minor hearing loss

80 dB for moderate hearing loss

90 dB for severe hearing loss