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Microphone Selection

Specifications

For this particular project, we needed a microphone with three specific characteristics:

  1. ) It needed to have a high acoustic overload point (AOP). This would allow the microphones to be located on the outside of the ear-cans, very close to a full-volume acoustic drum set, and still not distort. Our final mic choice has an AOP of 135dB.

  2. ) It needed to have a large signal to noise ratio (SNR). This means that the microphone will output a cleaner signal with less "hiss" sound during quiet times. Something with at least 60dB or great would work. Our ultimate choice was for a microphone that had 75dB SNR.

  3. ) It needed decent sensitivity. Something near the range of -35dB would do. Note, when this number gets higher, that means it's more sensitive. Because sensitivity is almost always expressed as a negative number, that means a "smaller" negative number is more sensitive.

To learn more about microphone specifications such as AOP, SNR, sensitivity, please check out this very informative document from InvenSense here:

I tried three other microphones before I found my favorite. Here is a table to show the others options, and how they compare in terms of mic specs.

Mic AOP SNR Sensitivity Notes
ICS-40180 124dB 65dB −38dB With the onboard op amp gain, this ultimately had too low of an resulting AOP for drums. It clipped a lot when I played loudly.
SPH8878LR5H-1 134dB 66dB -44dB Again, with the onboard op amp gain, this ultimately had too low of an AOP for drums. It clipped a lot when I played loudly.
VM2020 149dB 50dB -63dB With such a high AOP, this mic could definitely handle the loud drums without clipping. This was a huge win, and actually, I used these mics for quite a while. But then I started to notice that during quiet times, there was a significant "hiss" in the audio signal. This is because it is, in terms of audio microphones, not very sensitive (-63dB). In order to hear the signal at a decent level, I had to add 60dB to 70dB of gain in the WM8960, which also can add some hiss to the signal.
AOM-5035L 135dB 75dB -35dB The best combination of high AOP, impressive sensitivity and SNR. No clipping and no hiss. This one fits the job!

Options

Here are the four microphones we ultimately tested. Note, although for our application, the AOM-5035 was the right choice, you might like to consider trying out some of the other mics and see if they work for your use case. If I were making these for playing piano or any kind of quieter environment, I might go with one of the MEMs.