Operation Of The Instrument; Practical Measurement Conditions - Chauvin Arnoux CA834 Notice D'utilisation

4. OPERATION OF THE INSTRUMENT

4.1 Choice of measurement range
The sonometer has 3 set measurement ranges (30-80dB, 50-100dB, 80-130dB) and one
automatic measurement range (30-130dB).
To choose your measurement range, use the "LEVEL" push button.
If the "UNDER" or "OVER" symbols appear permanently on the sreen, it indicates that you
are using a measurement range that is too low or to high. In this case, press the "LEVEL"
push button.
Note : The automatic 30-130dB measurement range is a way of avoiding of these microphone
under / overload problems.
4.2 Choice of frequency weighting
Because the ear does not have the same aural sensitivity for all frequencies, filters are
used to weight or correct the measured levels according to the frequency.
There are two correction curves, A and C, provided on the C.A 834. To change from one to
the other, press the "A/C" push button.
The best-known curve is the A frequency weighting corresponding to the "average
international ear".
Generally, it is used for measuring nuisance levels in industrial premises.
The C curve is better suited to check for the presence of audio frequency noise (if the level
measured in position C is higher than in position A, it means that the signal includes
significant audio frequency components). This curve is also suitable for measuring musical
environments.
4.3 Choice of response time
Depending on the type of noise concerned (brief noise such as a car horn or an animal's
cry, or a drawn out noise like that of an industrial machine), it is necessary to choose a
suitable response time.
Two response times are available on C.A 834 :
- FAST (short response time) if the noise consists of brief impulses or if you are
only concerned with peak values. This is the mode most often used.
- SLOW (long response time) to measure the average sound level.
Changing from one to another is obtained by pressing the "FAST / SLOW" push button.
4.4

Practical measurement conditions

Hold the instrument in your hand and point the microphone toward the noise source to be
measured (see Precautions for use), the sound level will be displayed.
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