BRUEL & KJAER 1022 Instructions And Applications page 36

receiver room
411.5
2619
transmitter room
4145 L.S.
2619
Fig.5.14. Set-up for measurement of the sound insulation
properties of a wall
ing Amplifier 2606, the different sound levels picked up in the two rooms
are taken alternately and amplified before being fed to the Level Recorder.
The result is that two independent curves are automatically reproduced on
the recording paper, enabling the sound level difference between the two
sides of the wall to be read off in decibels. Such a recording is shown in
Fig.5.15. The sound absorbed by the receiving room must be taken into
account.
The main problems in the transmission and reception of airborne sound
are the power av;Jilable from the source and the signal to noise ratio of the
receiver. Both these problems can be eased if a narrow band noise source
and a narrow band receiver are used.
The Heterodyne Slave Filter 2020 has very narrow bandwidths and is
ideal for such measurements. It can also be directly controlled by the 1022.
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