I was doing some experiments with audio and wish to get "raw and unprocessed" data, and noticed that all the files had the following profile (just blowing into the mics):

enter image description here

Speaking to the microphone vendor, they mentioned - audio acoustic system will convert impulses into tail recovery dependent on the delay constants of the system which is dependent on system bandwidth.

Can someone explain what this means? What is the phenomenon called? Equations would be helpful as well.


  • $\begingroup$ Please document the complete signal chain. $\endgroup$ – Olli Niemitalo Apr 6 '19 at 4:34

The tail is most likely the impulse response of a high pass filter. All acoustic system are highpass by nature since air really can't transmit DC pressure. In addition many data acquisition systems have DC blocking filters and/or high passes build in to keep undesirable "rumble" signals that's below the range of hearing out of the recording.

Could also be in the microphone itself. It looks like you are hitting really hard and the recording is clipped. It takes a bit of time for the microphone and the pre-amp to recover from a major overdrive.

  • $\begingroup$ I did look at the codec settings, and I see a 4Hz Highpass filter applied. I tried it without the filter, and it seems worse (fair enough), but I still see the "tail-like" audio profile. Any insights on why this behavior persists? Thanks. $\endgroup$ – st_penn Mar 7 '19 at 22:30

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