Testo testo 815 Sound level-measuring apparatus, Noise-measuring apparatus 0563 8155 用户手册

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5.3 Measuring

Sound waves can be reflected off walls, ceilings and other
objects. Also the meter housing and the person measuring (if
measuring incorrectly) are disturbing factors in the sound field
and can lead to incorrect measurement results.

How to avoid measurement errors
The meter housing and the person operating the meter may not
only obstruct the sound coming from a certain direction but they
can also produce reflections and consequently serious
measurement errors. Experiments have shown, for example, that
the body can cause errors of up to 6 dB with frequencies of 400
Hz if a measurement takes place less than one meter away from
the person. This error is less for other frequencies but a minimum
distance should be adhered to. Generally, it is recommended that
the meter is held at least 30 cm - even better 50 cm - away from
the body. 

We recommend fitting the instrument to a tripod for exact
measurements.

Measuring
1 Switch on instrument
2 Set measurement time (”FAST/SLOW”)
3 Set frequency (”A/C”)
4 Set measurement range (”Level”)
5 Always direct the microphone exactly at the sound source to

be measured (reference direction).

6 Save the highest and lowest value via ”Max/Min” 

5. Operation