G.R.A.S. Sound & Vibration
Sound-intensity Probe Type 50AI - Page 10
2.
Input Channels
The Type 50AI has two input channels, one
for each microphone preamplifier. The chan-
nels are marked A and B on the remote-control
handle, see Fig. 2.1.
2.1
Preamplifier Inputs A and B
A and B refer to the two channels of the probe.
Channel A is reserved for the leading micro-
phone, i.e. the microphone first struck by an
acoustic wave front (see Fig. 2.2). When this
happens, this should be interpreted as a posi-
tive component of the sound intensity in the
direction from microphone A to microphone B.
2.2
Sound-intensity Axis
Fig. 2.2 illustrates the origin and direction of
positive sound-intensity vectors. This positive
direction is always from microphones A to B.
The origin of the sound-intensity axis lies on the
geometric centre of the pair of probe micro
-
phones.
Fig. 2.1 Showing the inputs and markings for
the two preamplifier inputs
Input for channel B
Input for channel A
Markings for chan-
nels A and B
