For the purpose of detecting a defect or failure in a machine, it is often practical to physically listen to any abnormal noises that a machine might be making, and even use a simple stopwatch to determine the frequency of these noises. This practice often gives clues as to what part of a machine is having problems.

For the purposes of detecting failure in a large plant, filled with many machines that might not have many sensors, one can also often isolate a machine with a problem by listening to abnormal ambient noises, and tracing them back.

Is there any sort of practice in which a microphone is placed at a certain location to detect the "ambient sound signature," and then is used as a sort of sensor for problems in plants? I can imagine a baseline being made with this microphone and then used as a reference for abnormal ambient noises, then paired with a monitoring camera to detect whether there is any explanation for non-regular noises.

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    $\begingroup$ Why not just put a vibration sensor on the machine - any abnormal frequencies become apparent... $\endgroup$
    – Solar Mike
    Feb 2 '18 at 22:32
  • $\begingroup$ Yes, there are systems for this. For instance. $\endgroup$
    – Phil Sweet
    Feb 2 '18 at 22:54
  • $\begingroup$ I've read an article about a similar system used on large pumps, but I've thrown it away two years back ... $\endgroup$
    – mart
    Feb 13 '18 at 9:30

The closest thing I can think of is Diagnostic Listening Devices such as STEELMAN 97220 Mini EngineEAR or the multichannel system that are regularly used in auto diagnostics, can also be used in plant machinery.


What's the end goal? Typically systems that do what you're talking about are critical, expensive equipment like large pumps and turbines that take time to shutdown and repair or where something like the failure of a bearing could destroy the entire machine. These systems use accelerometers attached near the critical components to sense the operating component's "signature".

Most factory equipment should be fine on a maintenance schedule though. You know, the "Replace these bearings and greases these joints every 5000 hr" kind of stuff.

In any case, I have seen production QC checks done on cast gear blanks using a microphone. The blanks were on a conveyor which ran through a small enclosure to reduce the influence of outside noise, there was a pneumatic "hammer" which would strike the gear and the microphone would pick up the ringing of the blank and compare it to the baseline.

I'm sure you could try doing something similar with a machine in a factory, but you would probably have to enclose it to keep other machinery from triggering a false alarm or masking a real issue. Creating a baseline acoustic profile for all of the different moving parts could be a complete mess.


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