General Tools and Instruments DSM8921 - Manual (Page 10)

3 Press the BA MODE key. F will be
displayed to the left of the SPL
(sound pressure level) icon. The
digital display will show the
background noise level.MAX HOLD
will be disappeared now. (See Fig.9)
4 Press the MAXHLD key again and
MAXHOLD will be displayed. (See
Fig.10) The meter is now ready to
measure the actual machine noise.
5 Turn on the machine you want to
measure and note the new sound
level reading. This number represents
the sound level of the device without
the background noise. If there is no
change in the reading, the
background noise is greater than the
noise of the device.
6 Press the MAXHLD key and then the
BA MODE key to exit background
noise absorber mode.
Fig.9
60
+10
FAST UNDR
A
Fig.10
60
+10
FAST
UNDR
A
MAX HOLD