Bone conductor
Bone conductor output
The maximum speech output level from the bone conductor depends on the actual sensitivity of the vibrator. The actual
maximum output is therefore determined at the time of calibration. The actual maximum output level may be determ-
ined by the operator by simply increasing the output level until the attenuator setting no longer increases.
Additionally, Madsen A450 includes a feature which allows the operator to select the maximum output level from a bone
conductor. Using this feature, the maximum output may be set lower than the physically available output level (installation
option).
As the maximum available output level will result in significant distortion from the bone conductor, the specification
below limits the speech output level to 60 dBHL. Typical distortion levels (median values of a sample of bone conductor)
are indicated in the following table.
Total harmonic distortion (THD), %
Speech hearing level (dBHL) ->
60
50
40
30
Frequency below (Hz)
-
-
-
-
250
34,7
13,7
4,4
2,2
500
3,7
1
0,3
0,2
1000
2,6
0,9
0,3
0,3
Frequency response
Frequency
(Hz)
Nominal response level
(dB re. 1kHz level)
Tolerance
(dB)
250
-1.5
±4
500
6.5
±4
750
1.0
±4
1000
0.0
0
1500
1.5
±4
2000
-6.5
±4
3000
-15.5
±4
4000
-11.0
±6
Madsen A450
99
12 Technical specifications
