Cell Phones

Microphone frequency response limited by Google Assistant

  • Last Updated:
  • Jan 1st, 2022 5:00 pm
[OP]
Deal Fanatic
Jan 21, 2018
7837 posts
8535 upvotes
Vancouver

Microphone frequency response limited by Google Assistant

I was trying to test an ultrasonic pest repeller by using the audio spectrum analyzer app Spectroid on my Moto G Power (2020) phone, and I noticed something odd: on this phone Spectroid showed a sharp cutoff in background noise above 8 kHz, and did not detect the ultrasonic tone at all. I tried some other phones, including earlier-gen Moto Gs, and they all showed fairly linear background noise up to 20 kHz and easily detected the ultrasonic tone from the repeller.

It initially looked like Moto implemented a built-in 8 KHz voice frequency filter on the mic of this phone that's not common to other phones. I wouldn't have suspected without this test, since of course I normally only use it for voice. There didn't appear to be any setting to turn the filter off, for example if you were recording music or bird songs.

But with a little more searching I found a hint that this is caused by Google Assistant. I found and turned off the setting that has Google Assistant always listening, and sure enough, the microphone frequency response recovered (after a restart). I wasn't even aware that Google Assistant setting was on by default on this phone, let alone that it silently limits the frequency response of your microphone to assist it in speech recognition. Bad Google!
1 reply
Deal Addict
User avatar
Oct 14, 2010
1724 posts
1196 upvotes
Barrie ON
Good job discovering the cause. I don't think I would have considered that. I will keep that in mind, since I just turned on this feature in my new phone. For now it is just for testing, but if it doesn't respond randomly, and it doesn't affect battery life, it sounds like a good idea.

It makes sense that they would reduce the pass through frequency to just the voice frequency to prevent random sounds from waking the assistant.

The only other time I might use the mic is with Shazam to identify songs. I suppose that recording a video might be affected also.

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