BRUEL & KJAER 2206 - Page 22

1f
3. Set the RANGE SWITCH for an on scale meter deflection and note the reading. This
is the background noise level of the room .
4 .
Play the 1 kHz calibration band (side A, band 1) and set the amplifier volume control
for a reading at least 1 0 dB higher than the background noise level.
5 . Play the measuring signals (band 2) and note the results on Graph Paper OR 2011.
At the lower frequencies, the reading may fluctuate considerably and the best eye-
average
should be taken.
Note that at the very high frequencies (above 10kHz) and at the low frequencies (below
100Hz) the output of most hi-fi systems will roll off. Hence it may not be possible to ob-
tain an adequate signal to noise ratio (at least 5 dB) to permit valid measurements .
It should also be noted that on the high frequency bands (10kHz and up) stylus mistrack-
ing may occur resulting in the generation of noise components at lower frequencies . If
the loudspeaker has a significant high frequency roll-off, the noise generated by possible
stylus mistracking may be of a higher amplitude than that which would have been pro-
duced by the desired frequency band and an erroneous reading may result.
If the above mentioned problems occur, they may be resolved using a precision Sound
Level Meter Type 2203 or 2209 equipped with a Third Octave Filter Set Type 1 61 6.