Acoustic Measurements in a Jet Flow

Sound measurement in turbulent air is hard to do as the flow around the microphone capsule creates acoustic disturbences which do not occur in undisturbed flow. By using hotwire probes it is possible to exactly measure both the mean flow velocity and the fluctuations. The small size of the probes reduces flow disturbences to a minimum.

The flow fluctuations (RMS values) can be extracted from the signal and can be made audible.

As an example we have measured the jet flow of a nozzle. The dots marked in red show the position of the hotwire probe. For comparison the surrounding noise was recorded using a standard microphone (in green).

Please click the measuring point to play the corresponding sound file. (Using a slow internet connection may result in a short delay. For the upper measuring point you should use head phones or loudspeakers capable of low frequencies.)