10 Jan Looking for Sound
“Where did that sound come from?” is a question often asked. It can also be a difficult question to answer. Most sound measurements are performed with single microphone sound level meters. These meters do not provide information about where a sound is coming from. If it is difficult to locate the source of the sound with our (directional) hearing, more advanced instrumentation may be required.
BKL has used the Norsonic Acoustic Camera 848 to identify the location of dominant industrial, marine, road, rail and indoor noise sources. The unit we have used uses real time processing with 256 microphones mounted in a 1m diameter disc to perform this analysis.
In the looped video example above, the location of a distant ship horn blast is obvious using the Nor848, illustrated with sound contours overlayed over video. Furthermore, the video demonstrates that audio playback is specific to the cursor location so the listener can also “hear” the sound that is arriving from different directions.
This instrumentation can be used to detect the location of the noisiest machine in a factory, the noisiest part of a piece of a machinery and sound leaks through walls. We have also used it to determine the effective height of rail shunting noise on a string of rail cars to assist with noise barrier design.