BRUEL & KJAER 2230 - Measurement Types Overview

ANSI Standards:
When performing measurements requ1nng the use of a Sound Level Meter to ANSI
standards, the free-field Microphone's characteristics should be adapted to a linear
random incidence response by selecting "Random" on the SOUND INCIDENCE switch.
Fig. 3. 7. Measurements to ANSI standards in a free sound field
In a truly diffuse-field, the Sound Level Meter can be oriented in any direction. Under
ideal free-field conditions optimum response is obtained by orientating the Sound Le-
vel Meter as shown in Fig.3.7. However, due to the directional response and the practi-
cal difficulty in orienting the Sound Level Meter correctly, a reduced accuracy may be
expected. For optimum accuracy, see Fig.3.5.
Measurements not requiring the use of an IEC or ANSI Sound Level Meter:
Measuring with a free-field microphone in a diffuse-field, or measuring with a linear
random incidence response microphone in a free-field results in small inaccuracies in
the values obtained. More accurate results will be obtained by selecting the appro-
priate microphone frequency response to suit the type of sound field.
Consequently, when adherence to IEC or ANSI Sound Level Meter Standards is not
required, the SOUND INCIDENCE switch should be set to "Frontal", under free-field
conditions or when the sound source can be located, and the meter should be pointed
directly at the sound source during measurements.
When measuring in a diffuse sound field, or when the Sound Level Meter is moved
around during the Leq measurement, the best accuracy is obtained by setting the
SOUND INCIDENCE switch to "Random".
3.5.3. Sound Measurements
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The 2230 offers 5 basic measurements which are: SPL, Min, Max, Leq and SEL. All 5
functions are carried out together and can be displayed successively. To cope with
different kinds of measurement situations, DETECTOR mode, FREQUENCY WEIGH-
TING, etc can be set independantly. The user should therefore be aware of the require-
ments of any standard with which measurements should conform.
All five measurement functions are carried out at the same time. The digital display
gives the measurement selected by the DISPLAY switch, while the quasi-analogue dis-
play constantly gives the current SPL with a 2 dB resolution. Thus, the quasi-analogue
display, allows the user to compare the current SPL with the measuring range, and
possibly to adjust the latter to suit the SPL during measurements.