The Stenger principle states that when two tones of the same frequency are
introduced simultaneously into both ears, only the louder tone will be
perceived. The test is performed by introducing a tone of a particular
frequency into the better ear at a level 10 dB above threshold. If the loss in the
poorer ear is genuine the patient will be unaware of any signal in his poor ear
and will respond to the tone in his good ear, since it is 10 dB above threshold.
This is a negative Stenger result. If the patient does not respond, it is a
positive Stenger. If the tone is above true threshold in the bad ear it will
preclude hearing the tone in the good ear. As the patient does not want to
admit hearing in the bad ear, and is unaware of the tone in the good ear, he
does not respond.
The test is only valid if the difference between the two ears is 20 dB or more.
8.4 RAINVILLE TEST
The Rainville test is used to determine the bone conduction threshold
without testing the other ear. The test consists basically of masking
ipsilaterally by means of the bone vibrator.
If “Ma” is the masking level just necessary to mask the air tone threshold (Ta)
on the same ear, and if “Mb” is the bone masking level just necessary to mask
the pure tone bone conduction threshold (Tb), then Ta = Ma - X and Tb = Mb -
X, where “X” equals the difference in intensity level in order to obtain effective
masking. This difference is usually 3 dB.
It is known that, for threshold, the cochlea receives the same energy in both cases
of air threshold and bone threshold, so Ta may be masked by Ma or Mb.
We can then obtain Mb versus Ta, because Mb is the quantity of masking
necessary to mask Ta. Tb is then equal to Mb -X.
To access the Rainville test, select:
Special, Rainville
The following display appears:
Freq.
Air
R:Tone Bone
NBN
1000 Hz
C/P/W
20 dB
On/Off 20 dB
This setup routes a pure tone signal in the stimulus channel to the right
earphone, and selects narrow band noise to the bone vibrator in the masking
channel.
Place the right earphone and the bone vibrator on the ear being tested.
Present a pure tone in the earphone and adjust to approx. 5 dB above
threshold (pulsed tone may also be used).
Increase masking in bone vibrator until effective masking is obtained. The
bone threshold may now be evaluated by subtracting 3 dB (or X depending
on calibration) from the masking attenuator setting.
MIDIMATE 622 OPERATION MANUAL
8. Special Tests
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