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I have come across many terms to describe different types of recorder calibrations (e.g., end-to-end calibration, point calibration, factory calibration) and the whole topic of recorder calibration was very confusing for me when I started in bioacoustics. I had a hard time finding beginner-level (i.e., not highly technical, jargon-filled) material describing calibration, and even now, I still at times question whether I'm using the correct terminology.

I was wondering if anyone would be able to provide a concise summary of the different types or methods of recorder calibration and perhaps when they might be more or less recommended.

I also wonder if the calibration categories and recommendations tend to be similar for air and underwater recordings. (For me, I have only worked with underwater recorders, so I'm not very familiar with air recording methods.)

Thank you for any help you can offer!

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    $\begingroup$ You must have read my mind -- I was just googling this very thing! $\endgroup$ Jul 2, 2022 at 23:08

3 Answers 3

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I looked up the Bible of Underwater Acoustics (Urick 1983) and found the following overview enter image description here

There are 12 methods mentioned with 27 references!

Anyhow, the simplest method is to compare the sensor in question with a calibrated one. In underwater you compare the recording with the direct measurements of a calibrated hydrophone.

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From a terrestrial sound perspective, I've seen analogous calibration methods to those pointed out by @WMXZ. See chapter contents from [i] below.

enter image description here

On a regular basis though, I've only so far seen the substitution method (measuring the playback sound with a quality calibration mic, and then switching it with the target mic and comparing the recorded signals.

References

i) Wong, G.S. (2014). Microphones and Their Calibration. In: Rossing, T.D. (eds) Springer Handbook of Acoustics. Springer Handbooks. Springer, New York, NY.

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You can either:

  1. Trust the cal sheet of the microphone
  2. use a pistonphone to check sensitivity at one frequency (typically 250 or 1000 Hz)
  3. do a relative calibration where you measure a sound field with a known microphone and then insert your unknown microphone in the same sound field to work out its sensitivity.
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