Zeisberg GmbH
Tone audiometry, bone conduction KA450
- Lango: Language and translation manager
The following audiometer settings must be made:
Transducer selection (1) Bone receiver (4)
Side (6) right (8) or left (7) (better ear)
Signal selection (9) Sound (12)
Frequency (52, 53) 1000 Hz
First, the bone receiver is placed on the mastoid of the better ear. The earpiece should be positioned so that the sound is heard at its loudest. The air receiver is also placed on for anaesthesia, whereby the receiver of the measuring ear is placed on the temple so that the measuring ear is not closed.
The control elements now have the same functions as for measuring the air conduction, i.e. the dB controls (42, 47) are used to set the signals for the bone conduction and the masking noise on the opposite side.
If the test side is set to "right", the masking noise is automatically on the left side of the receiver.
The recording is now carried out in the same way as an air conduction threshold measurement. The measurement points in the audiogram form are marked with symbols as described in [2], for example, to avoid confusion with the air conduction threshold.
When changing the side to be measured, both the bone and the air receiver must be reattached in accordance with the above instructions.
Note:
The volume of the bone receiver cannot be set as high as that of the air receiver.
The ">100 dB" function (57) cannot be activated.
The frequencies 125 Hz and 8000 Hz are not available.
Due to the physical limits of the bone conduction earphone, the distortion factor increases depending on the frequency and level to an extent that can lead to incorrect measurements. This affects bone conduction measurements at 250 Hz above 20 dBHL and measurements at 500 Hz above 50 dBHL.
Avoidance of incorrect measurements due to the emission of airborne sound through the bone receiver:
When determining hearing thresholds at 3 kHz and higher frequencies with the B-71 bone receiver, it must be noted that the bone receiver emits sound energy into the air. Depending on the volume and the patient, this may be perceived louder through the open auditory canal than the actual bone conduction. To avoid this, it is advisable to insert a sound insulation plug into the ear on the test side at these frequencies and to cover the contralateral side with dust.
At the following frequencies, the airborne sound emitted by the B-71 bone conduction receiver is greater than the corresponding bone sound by the level differences specified below (mean values, maximum values in brackets):
3 kHz 4.0 dB (18 dB)
6 kHz 10.5 dB (31 dB)
(see also technical data)
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