BRUEL & KJAER 2203 Instructions And Applications

5. OPERATIONAL CHARACTERISTICS
AND ACCURACY
5.1. DIRECTIONAL CHARACTERISTICS
Ideally a sound level meter should have the same sensitivity for sound
coming
from all directions. Unfortunately this cannot be achieved in
practice except in the case of relatively low frequencies .
For
higher frequencies, when the dimensions of the sound level meter
and microphone are comparable to the wavelength of the sound, the
sound field around the instrument will be disturbed and the pressure on
the Microphone diaphragm will depend on the direction from which the
sound is coming .
The
directional characteristics of the 2203 with Microphone Type
4145 are shown in Fig.5.1. Although response is very uniform at
angles of incidence of less than 30°, high frequency response is re-
duced at
angles greater than 30°.
The omnidirectivity of the instrument becomes more important when
the sound is incident from all directions. Such examples are noise from
several sources in a machine shop or noise from a single source in a
room
with reflections from hard boundaries making the field more or
less diffuse. Under such circumstances, the Random Incidence Correc-
tor, fitted in place of the normal protection grid on the one-inch Micro-
phone gives enhanced overall characteristics. The effect of the Random
Incidence Corrector can be seen from a comparison of Figs.5.2 and 5.3.
These curves are valid for the Mi-crophone mounted away from the
2203 which can be achieved using Extension Cables AO 0033 or AO
0059.
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BRUEL & KJAER 2203 Specifications

General

Brand	BRUEL & KJAER
Model	2203
Category	Measuring Instruments
Language	English