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Phased Array Microphone (2023)

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Re: Phased Array Microphone (2023)

#101

Post by KeplerBoy »

jpc0 wrote: post #98
KeplerBoy wrote: post #66

Earlier quoted context omitted.

By definition, sure. But one always needs some effect which changes some electrical property. We can't just hook up an ADC (analog digital converter) to thin air and hope for the best. In practice most microphones measure the displacement of microscopic membranes, which are deformed by the air pressure. The next question then becomes how to measure microscopic movements of a tiny membrane. Turns out the membrane form…

That is not necessary true. There are at least 4 different types of microphones. Condenser which does in fact form part of a capacitor, dynamic which is effectively a linear generator (coil attached to membrane), ribbon which is a change in resistance as a small ribbon flexes and piezoelectric which is some black magic witg crystals

Sure, that's why I wrote most microphones.

There are also some exotic principles like laser or radar microphones using interferometry.

https://en.m.wikipedia.org/wiki/Laser_microphone

https://ieeexplore.ieee.org/document/7808865

Re: Phased Array Microphone (2023)

#102

Post by unwind »

repiret wrote: post #53
FredPret wrote: post #22

Earlier quoted context omitted.

I had no idea they were mammals until this comment. I thought they were furry birds!

It is not unreasonable to think of bats as flying mice.

In Swedish that is almost exactly what they are called, bat translates to "fladdermus" which is "fladder" (flutter) and "mus" (mouse).

Re: Phased Array Microphone (2023)

#103

Post by markhahn »

cma wrote: post #90

Could this be combined with a smaller number of high quality mics and then machine learning or something else incorporating them to boost the overall quality while maintaining all the other features?

afaik, it really depends on the spatial structure of the audio field.

think nyquist sampling rates, applied to space, and you can't apply a low-pass filter just because you don't care about higher-order signals. that means that for any given audio environment, there will be some "spatial spectrum" of signal, and you need to sample it densely enough to avoid aliasing.

Re: Phased Array Microphone (2023)

#104

Post by neumann »

dllu wrote: post #3

I once did a project to do multilateration of bats (the flying mammal) using an array of 4 microphones arranged in a big Y shape on the ground. Using the time difference of arrival at the four microphones, we could find the positions of each bat that flew over the array, as well as identify the species. It was used for an environmental study to determine the impact of installing wind turbines. Fun times.

That sounds super interesting. Is there a write up somewhere of the project?

Re: Phased Array Microphone (2023)

#106

Post by jpc0 »

KeplerBoy wrote: post #101
jpc0 wrote: post #98

Earlier quoted context omitted.

That is not necessary true. There are at least 4 different types of microphones. Condenser which does in fact form part of a capacitor, dynamic which is effectively a linear generator (coil attached to membrane), ribbon which is a change in resistance as a small ribbon flexes and piezoelectric which is some black magic witg crystals

Sure, that's why I wrote most microphones. There are also some exotic principles like laser or radar microphones using interferometry. https://en.m.wikipedia.org/wiki/Laser_microphone https://ieeexplore.ieee.org/document/7808865

I think popular is very situational though.

For me I see a lot more dynamic than condensers but I guess if you are talking about what is in like every single IOT thingamabob then you might be right there.

Re: Phased Array Microphone (2023)

#107

Post by sanderjd »

jpc0 wrote: post #98
KeplerBoy wrote: post #66

Earlier quoted context omitted.

By definition, sure. But one always needs some effect which changes some electrical property. We can't just hook up an ADC (analog digital converter) to thin air and hope for the best. In practice most microphones measure the displacement of microscopic membranes, which are deformed by the air pressure. The next question then becomes how to measure microscopic movements of a tiny membrane. Turns out the membrane form…

That is not necessary true. There are at least 4 different types of microphones. Condenser which does in fact form part of a capacitor, dynamic which is effectively a linear generator (coil attached to membrane), ribbon which is a change in resistance as a small ribbon flexes and piezoelectric which is some black magic witg crystals

Fascinating. Is there a book about the history of microphones?

I find this to all be in the realm of "I don't believe you that any of this works at all" if I didn't have a lifetime of experience with the fruits of successfully-functioning microphones.

Re: Phased Array Microphone (2023)

#108

Post by cyberax »

redblacktree wrote: post #99
lscharen wrote: post #67

Earlier quoted context omitted.

Reminds me of Intellectual Venture's Optical Fence developed to track and kill mosquitoes with short laser pulses. As a side-effect of the precision needed to spatially locate the mosquitoes, they could detect different wing beat frequencies that allowed target discrimination by sex and species.

Where can I buy one?

I don't think you can. This kind of laser devices is wildly dangerous.

Re: Phased Array Microphone (2023)

#109

Post by t0mas88 »

psunavy03 wrote: post #93
Marthinwurer wrote: post #27

Earlier quoted context omitted.

I love these kind of inadvertent measurements. One of my favorite examples is that a sufficiently accurate IMU can get you relatively accurate longitude measurements from the Coriolis effect.

I believe this is one of the initial steps an aircraft INS uses to find north while it is aligning, but it's been too long since I had aircraft systems theory in the front of my brain.

Yes, from earth rotation the INS could figure out true north if the latitude is known. Or figure out the latitude if current heading is known. But normally it's aligned with a starting position from pilot input or GPS.

Re: Phased Array Microphone (2023)

#110

Post by KennyBlanken »

amluto wrote: post #59
entropicdrifter wrote: post #38

Earlier quoted context omitted.

It does act as a thermometer, if and only if the altitude remains constant. The speed of sound fluctuates with both temperature and altitude

I’m not sure how the speed of sound could depend on altitude, even in principle. The air doesn’t know where it is! Putting that aside, in an ideal gas, the speed of sound depends on the composition of the gas and the temperature and, interestingly, does not depend on pressure, and pressure is the main way that the altitude would affect the speed of sound. So measuring the speed of sound in air actually makes for a pr…

From your own link:

"The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior."

"The speed of sound is raised by humidity. The difference between 0% and 100% humidity is about 1.5 m/s at standard pressure and temperature, but the size of the humidity effect increases dramatically with temperature."

"Slight" can matter significantly in an application like this.

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