Natural Science Forum / Physics / Acoustics / July 2007

You have to give/get more information,
or preferably get hold of a vibration calibrator.
What was the reference for the dB values?
If that LD824's last calibration was with a microphone on the same
preamplifier,
there might be some hope if you know the sensitivity of that microphone.
(But I am on vacation)

If you had a vibration calibrator you possibly could calibrate the SLM to
show dB re. 1 micrometer/s2  (a0 = 10^-6 m/s2)
then 20 log(a0) = -120 dB,  and 10 m/s2 would be 140 dB.
Then the measured acceleration  a = 10^((La-120)/20)  m/s2
where  La is the measured acceleration level in dB re. a0.

Asbjørn

I usually send the signal from an audio oscillator into the input
terminal of accelerometer amplifier and note the response. Then I set
the dB scale for a convenient value.

Ise any reference you want.

it's usually dB re one g RMS, or dB re one micro-g RMS.

The accuracy of your voltmeter that you use to measure the ac voltage of
the oscillator, and attenuator setting precision, becomes your accuracy
of measurement display.

Angelo Campanella

Vey simple, assuming (i) you are using an ICP-type accelerometer with
a voltage (not a charge) output, and (ii) the SLM is correctly
calibrated for a 50 mV/Pa mike, as is usual for an L-D824:

1 g will produce 100 mV, but the L-D824, set to expect 50 mV/Pa,
thinks it is seeing 2 Pa. 1 Pa is 94 dB, so 2 Pa = 1g is 97 Pa. 3.16 g
= 107 dB, 10 g = 117 dB, 0.1 g = 74 dB, and so on.

By the way, how do you download a sound level meter?

Bob Hedeen