Question: Deconstruct a waveform into its fundamental frequencies


I have a sample waveform of an air conditioner and want to see if any low frequencies (10 Hz which is harmful to human health) exist in the wave.  How can I do that?


Granted the frequencies picked up in the recorded file depend on the quality of the recording and the recorder and lower frequencies may not have been picked up. 


I've looked at which describes similar deconstructions, however the source of the original wave is a construction of functions of x and I'm dealing with a list of point values. 

plots:-listplot(c) #viewing the waveform


How do I work with the point values to extract fundamental frequencies?

Here is the sample .wav file...

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