3.5mm/USB Stereo Microphone Could Make Cheap 2-Mic Array

We previously wrote about the possibility of using Sony PS3 Eye camera as an inexpensive 4-mic array as at the time (August 2019) it sold for $7.5, and can still be found for $13 on Amazon. But I’ve come across a potential even lower-cost option with a tiny stereo microphone that connected to the 3.5mm audio jack on your phone or computer and sells for a couple of dollars ($2-$5) on sites like Aliexpress ($2.15) or GearBest.

There’s not much in the way of specifications:

• Uni-directional stereo condenser microphone
• Left and right channel stereo recording
• Gold plug for maximum conductivity and minimum noise
• Sensitivity – 38 ± 3dB
• Frequency Response – 100-15,000Hz
• Plug – L-shap gold-plat mini plug, 3.5mm
• Dimensions – 5.7 x 5.5 cm

If you click on the GearBest link, you’ll find there’s both a “mobile phone ” version and a “PC” version. I supposed it was because of different connectors, but I was not sure and found the starting point of the answer on Quora:

Your android phone uses a form of socket (TRRS) that can accept up to 2 channels of sound input (stereo sound from a microphone) and 2 channels of stereo output to headphones.

Good at least we know stereo audio should be supported on smartphones via the 3.5mm audio jack. The answer is Quora appears to be incorrect, as while two contacts are used for stereo output, only one contact is used for microphone input, and the other is for GND. So that should mean both L and R signals are mixed into a single mono microphone input.

Then I found out computers were typically using a 3-contact TRS jack instead (Wikipedia).

Some recent computers rely on the same TRRS jack as found on phones. If you get the wrong version, it’s not ideal, but fixable with TRRS<->TRS adapter.

Many mobile phones and SBC don’t come with an audio jack at all, and sometimes the microphone is sold with a Micro USB cable apparently to be used with GoPro Hero cameras, but I’m not sure why since the microphone are so close to each other…

It’s useful for some at least, as this stereo microphone looks very much like Olympus ME-51S Stereo Microphone sold for $30+ on Amazon as one person had a specific use for it:

I ordered this specifically to use for recording auto exhaust sound when making driving videos using a GoPro GoPro HERO4 Silver. I used Levalier mics before, but those are mono and the GoPro, for me at least, sent all the sound to a single channel. That’s no big deal when watching on a mobile device or even computer, but on a full sized system it was disappointing. Those cheap mics also blow out as decibels increase.

This mic works perfectly for my stated purpose. I clip it to my rear license plate frame, which sits less than 12″ above my exhaust, and I get clear, undistorted, full dynamic range exhaust sound in stereo.

So it looks like there’s a bug in the GoPro, and this type of microphone provides an easy workaround not requiring extra editing work. There are also hundreds of user reviews on Aliexpress for the $2.15 model, and most people seem to like the microphone to record videos with better sound quality.

Now can it be used as a cheap microphone array? I have not seen it tested yet for that purpose, but I don’t see why it would not be possible…

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