# Can two microphones placed within centimeter distance together measure a distance of the sound source?

I have placed two microphones placed within 1 or 2 cm distance. They can receive and record sounds around them. I want to detect the distance of the sound source (specially human voice) and the direction of the sound source using those microphones. Is it feasible when the distance of the sound source is short (i.e. around 10 cm).

• two microphones can detect direction, not distance May 7, 2022 at 19:15
• Any way to estimate distance from microphones? Even using more than two mic? @jsotola May 7, 2022 at 19:21
• think about it ... a pair of microphones can be used to determine the direction of the sound source ... adding a third microphone gives you three pairs of microphones May 7, 2022 at 19:25
• I suppose you could have multiple pairs of microphones arranged far apart and find the triangulate/find the intersection between directions indicated by each pair but they would need to be far, far apart or surrounding the target. May 7, 2022 at 19:29
• Yes, but why do you need to determine the distance? What use is knowing the distance from someone's ears to their mouth? Your question says the microphones are 1 - 2 cm apart - now you're mentioning earbuds which would be the width of a head apart. Can you see why your readers could be confused? May 7, 2022 at 22:04

A sound source and listening device can only provide direction.

Multiple microphones is how passive submarine sonar works. This will give direction only. Note that microphones in a line can only provide the two mirror image directions, you can't discriminate from off-axis sounds from either side.

To get distance, you need an active sound emitter, and measure the time for the reflection to return. This is how radar works as well, but with radio waves.

• Well, in theory (hah) if you know the dispersion curve of the media (atmosphere) and the structure of the source signal, you could analyze the relative arrival time of different frequency components. I wouldn't put a lot of faith in this approach. May 9, 2022 at 13:14

If the distance you want to measure is small than maybe you can use one of the microphone as a sound source.

But using a active sound emitter would be a better option.

For an unambiguous distance in 3d space you need 4 mics. The spacing needs to be a reasonable proportion of some function of the wavelength and the distance. The more mics you add the better the error.

Thinking about it there are at least two approaches. The first, which is generally applicable in open air, is to use two widely separated intensity probes (4 mics each), to get a vector from each to the source. Where the vectors meet is the location of the source.

The second in a room would only work with non stationary signals. Simply put a mic in each corner (ie 8 mics again) of the room and use the cross correlation between the channels to find the time delay. Then do some geometry.