Frequency of Gas Leaks

It will be white noise.

The reason for this question is as follows.

I need to build a test rig for an sonic leak detector, these detectors respond to a frequency of 20kHz to 25KHz. although any leak is as you say white noise there are main fundamental frequency's that predominate.

The predominant frequencies will, I believe, be mainly determined by the size and shape of the orifice through which the leak occurs. The pitch of a wind instrument changes only a little over a significant range of pressures, but more rapidly with changes in the dimensions. Think of your leak as a tiny whistle.Tiny does imply very high frequency (which is why it takes a pretty big leak for me to hear it...).

Or it may be EVP .......

I use an ultraphonic device to measure leaks in a valve and i set it at 40

sensitivity of the same needs to be adjusted for different applications though,

but 40 k works.

25k may not be the right freq for leaks,

Regards

Naveen

The pump size and speed and the shape and the size of the orifice are ?

Peter-H

I believe you should be looking for decibels ,dB, rather than frequency.

Air escaping through an orifice from a source exceeding approx. 13 psig will be at sonic velocity. A big hole will make more noise than a small hole but the frequency will be approximately the same. Also sound, dB's, attenuate with the square of the distance from source to measurement.

If I whisper "hello" or shout "HELLO" the frequency will be similar. The difference in noise will be the higher decibels of the shout. Should I chance to sing "h-e-l-l-o" in high falsetto or bombastic baritone the frequency may be slightly different but the ability to detect will still be volume or decibels.

Sound (pun intended) plausible? Tom

I think you could use the ISA standard on the noise detection formula of control valves

ISA-75.17 1989.