Chapter 3 – Taking Measurements
Influence of Instrument and Operator
BB 1219 – 11
35
Integrating Sound Level Meter Type 2239 A
User Manual
4. Press to move the next parameter (the month). Use
and to set the current month.
5. Repeat step 4 until you have set the current year, hour,
minute, and second. If you want to adjust a previous pa-
rameter (for example, to set the day after you have set
the year), then press repeatedly to cycle back through
the set-up windows.
6. To store the new date and time, press or . It is not
possible to cancel Date/Time changes. You will then return
to the Measurement Window.
3.5 Influence of Instrument and Operator
When measuring noise with a sound level meter, precautions
should be taken to minimise the influence of the instrument
body and the operator. The instrument’s influence is docu-
mented in Fig. 6.3. Type 2239 A is designed to have minimal
influence on the measurement.
The operator’s influence cannot be documented in the same
way, but the human body does act as a reflector of sound.
Experiments have shown that, at frequencies of around 400 Hz,
errors of up to 6 dB can be caused by reflections from a body.
It is obvious that a body blocks sound coming from behind.
The operator’s influence is often minimised by using a micro-
phone extension cable and by mounting the microphone and
preamplifier (or the sound level meter) on a tripod (see
Fig. 6.4). However, in most cases, it is sufficient to hold the
Fig.3.14 The Date/Time Set-up Window
SET-UP
Date/Time
>04 Jan 2001
22:15:02
bb221911.book Page 35 Tuesday, July 24, 2001 11:23 AM
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