[HN Gopher] Phased Array Microphone (2023)
___________________________________________________________________
Phased Array Microphone (2023)
Author : bglazer
Score : 285 points
Date : 2024-11-22 17:10 UTC (5 hours ago)
(HTM) web link (benwang.dev)
(TXT) w3m dump (benwang.dev)
| amelius wrote:
| Nice. It would be cool if this project could cleanly separate
| sources based on location.
|
| That would be a bit like a lightfield camera, where you can edit
| the focusing parameters after the image has already been taken,
| but now with sound.
|
| https://en.wikipedia.org/wiki/Light_field_camera
| hinkley wrote:
| I'm still sad these didn't become a thing. I don't need a 48MP
| camera phone. No seriously. I do not.
| miloignis wrote:
| I believe it can, there's a demo under the "Directional Audio"
| section, unless I misunderstand you.
| dllu wrote:
| 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.
| mywacaday wrote:
| I would love to do something like that to track the bats in my
| garden, how feasible would it be for an amateur to do as a
| personal project? Any good references on where to start.
| ryandvm wrote:
| Honestly, that sounds like amazing work. I wish I could afford
| to get out of enterprise software engineering and just do
| academic software development like that.
| jessetemp wrote:
| What were the results of your study? I've heard that bat lungs
| are so sensitive that when they fly across the pressure
| differential of large turbines their capillaries basically
| explode
| FredPret wrote:
| I had no idea they were mammals until this comment. I thought
| they were furry birds!
| repiret wrote:
| It is not unreasonable to think of bats as flying mice.
| unwind wrote:
| In Swedish that is almost exactly what they are called, bat
| translates to "fladdermus" which is "fladder" (flutter) and
| "mus" (mouse).
| bafe wrote:
| I did a similar project at 18. Needless to say I didn't have
| enough HW and SW skills to do much since I implemented the most
| naive form of the TDOA algorithms as well as the most
| inefficient way of estimating the time difference through cross
| correlation. I still learnt a lot and it led me to eventually
| getting a PhD in SAR systems, which are actually beamformers
| using the movement of the platform instead of an array
| isatty wrote:
| > bats (the flying mammal)
|
| As opposed to?
| Rygian wrote:
| Baseball bats?
| bgoated01 wrote:
| Here is a nice article on a study of baseball bats using
| microphones. https://www.acs.psu.edu/drussell/bats/papers/A
| cousticsToday_...
| lscharen wrote:
| 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.
| redblacktree wrote:
| Where can I buy one?
| cyberax wrote:
| I don't think you can. This kind of laser devices is wildly
| dangerous.
| NL807 wrote:
| That sounds like a fun project. Was it part of a research
| grant?
| neumann wrote:
| That sounds super interesting. Is there a write up somewhere of
| the project?
| crote wrote:
| I'm a bit surprised by those long "arm" PCBs. They are already
| doing calibration to account for some relatively large offsets:
| why not place each sensor on its own PCB, mount them to some
| carrier structure, and let calibration deal with the rest?
| elictronic wrote:
| Pcb manufacturing is cheap. I put 20 parts 1.5 inch by 24 inch
| into pcbway and ended up with final delivered cost of 240
| dollars.
|
| Not having to deal with wiring that many individual boards and
| all days of headaches tracking down issues is well worth it in
| my book.
| brunosan wrote:
| Armchair comment. I would LOVE to be a grad student again and try
| to pair it with ultrasound speaker arrays, for medical
| applications. Essentially a super HIFU (High-Intensity Focused
| Ultrasound) with live feedback.
| https://en.wikipedia.org/wiki/Focused_ultrasound
| brudgers wrote:
| Then, why not be a grad student again?
| 01100011 wrote:
| Maybe they want to afford dinner?
| polishdude20 wrote:
| Hey saw your message a while back in a thread talking about
| continuous glucose meters and feeling tired and fatigued
| etc. Mind contacting me? I'd love to chat. My email is in
| my profile
| brudgers wrote:
| TANSTAAFL, but student loans too.
| always_swapping wrote:
| I may be the FUS grad student you seek. Reach out via profile
| email if you want to chat. Cheers!
| etrautmann wrote:
| Medical applications would presumably require contact coupling
| and not through air?
| proee wrote:
| What is the most practical application for this technology? Could
| you use it to pinpoint sounds coming from a car like a squeak?
| Salmonfisher11 wrote:
| A similar technique is very popular in industrial automation to
| spot leaks in compressed air pipes and their connections from
| far away. These leaks are extremely loud in the ultrasonic
| range. It's overlayed with a camera picture.
|
| That's ultra expensive gear.
| spankalee wrote:
| I've always wanted this for videoconferencing room. A
| microphone array around the screen should be able to
| dynamically focus on the active talkers and cancel out
| background noise and echos to get much better sound quality
| that the muddy crap we usually get.
|
| If there were a speaker array around the screens too, you might
| be able to localize the audio for each person so that it seems
| like the sound is coming from where their head is on the
| screen.
| icegreentea2 wrote:
| Shure sells a variety of array microphones (and the software)
| that handles similar things. I've never used one, but heh.
|
| https://www.shure.com/en-US/products/microphones/mxa710
|
| https://www.shure.com/en-US/products/microphones/mxa920
| Salmonfisher11 wrote:
| Beamforming is standard in modern conference room gear. It's
| being used for making a video focus on the active speaker and
| optimizing his audio.
|
| Have a look at the "Meeting Owl" for example.
|
| It works great up to a limit (around 5m) then you will need
| additional microphones closer to the speaker.
| markedathome wrote:
| Microsoft Research had papers on speaker arrays that allowed
| speaker focus and noise cancelling a couple of decades ago. I
| think the technology eventually ended up in the Kinect.
|
| I think Cisco had something similar in their large screen
| meeting room video conferencing systems that could do
| positional audio tracking of multiple people. Could be wrong,
| but I think that was at least 10 years or so ago, if not
| more.
| bongodongobob wrote:
| You just need to buy actual video conferencing gear, this is
| par for the course.
| __MatrixMan__ wrote:
| I wish could rent one to figure out which device in my office
| has a squealing capacitor. I can hear it well enough to be
| driven crazy by it, but not well enough to find it. I start
| disconnecting things to narrow it down but then convince myself
| that it's my ears ringing.
|
| I'm unsure if I'll age out of this problem, or if worse hearing
| will just recreate it at different thresholds.
| adrianmonk wrote:
| You might have some luck with a spectrum analyzer app[1]. A
| fixed-pitch whine should show up as a line on the waterfall
| graph. If you move the phone around to differently locations,
| you might see the line getting stronger or weaker. You can
| also try rotating the phone to different orientations to see
| if it is coming from a particular direction.
|
| I used this to locate an annoying squeal coming from some
| equipment at work once. And to confirm that it wasn't
| imaginary.
|
| ---
|
| [1] On Android, I like these two:
|
| Spectroid (https://play.google.com/store/apps/details?id=org.
| intoorbit....). If you use this, consider turning on the
| waterfall display in the settings.
|
| Spectral Audio Analyzer (https://play.google.com/store/apps/d
| etails?id=radonsoft.net....). This has more color options for
| the waterfall display.
| hammock wrote:
| The tech is beamforming .. the applications are AV
| conferencing, camera tracking, voice lift, or sound
| reinforcement
| cushychicken wrote:
| This is more or less the same principle of how Amazon Echo
| devices work, but on steroids.
|
| Very neat. I would be surprised if you aren't seeing some
| diminished marginal returns from all those extra mics, but I
| guess you're trying to capture azimuth deltas that Echo devices
| don't really care about.
| Salmonfisher11 wrote:
| If somebody wants to play around with Zynq 7010's - have a look
| at the EBAZ4205 board. They can be bought from Aliexpress
| (20-30EUR). These are former Bitcoin Mining controllers.
|
| Some people reverse engineered the entire thing. It can be found
| in GitHub. And there's an adapter plate available for getting to
| the GPIOs.
|
| For a less complex entry there are also Chinese FPGAs ("Sipeed"
| boards which use a GoWin FPGA. They are quite capable and the IDE
| is free.
| telgareith wrote:
| Xilinx tool chain is also no-cost.
| gravypod wrote:
| I was just doing research and landed on this exact page last
| night! I was wondering if anyone knows how someone could mic a
| room and record audio from only a specific area. For my use case
| I want to record a couch so I can watch TV with my friends online
| and remove their speech + show noise from the audio. Setting up
| some array of mics and using them for beam steering would
| probably work but there's not a lot of examples I could find on
| GitHub with code that works in real time.
| imbusy111 wrote:
| From the article "The simplest method of beamforming is delay-
| and-sum (DAS)". Measure distance from a point (couch) to each
| microphone, delay the signal in time domain by the time the
| sound takes to travel from point (couch) to microphone, and add
| up the signals. Pretty trivial. Basically you want the
| microphones receive the couch signal at the same time, even
| though they are different distances away.
|
| Make sure there is enough variation in microphone distances for
| this method to be effective.
| crazygringo wrote:
| Loud show noise and your online friends' nearby audio is going
| to be reflected around the room as well as off of your bodies.
|
| What you want isn't microphone or beamforming tech, it's echo
| cancellation the same as every videoconferencing software uses.
|
| You just need to feed the show audio and friend audio in, and
| apply echo cancellation to each.
| killjoywashere wrote:
| I wonder how well this would work with laser microphones on a
| pane of glass. Can you infer keystrokes with near infrared laser?
| That is, can you identify the heatmap of keystroke events to
| infer which keyboard they're using, then replay the tape to
| identify the strings of characters being typed? Can you localize
| the turning of pages with UV?
| Salmonfisher11 wrote:
| Didn't Israeli students show that you can recover audio from
| the vibrations of bulb filament with a fast photo diode?
|
| I'd test that with a CCD line sensor plus a wide aperture lens
| and reading it out with 8kHz. Then you have 128 audio pixels
| that can cover an entire city.
| killjoywashere wrote:
| Line of sight might be an issue there. I'm thinking more
| high-end clandestine eavesdropping. Fun fact: curtains are a
| pretty good defeat for laser microphones, but if the building
| is really old and made of solid stone, you can point at the
| rock instead!
| 0cf8612b2e1e wrote:
| The rock?! That's incredible. I would have guessed it was
| too dense to pick up normal speaking volume. Then again,
| even the window glass vibration seems pretty magical to me.
| frankus wrote:
| "As part of the calibration, the speed of sound is also a
| parameter which is optimized to obtain the best model of the
| system, which allows this whole procedure to act as a
| ridiculously overengineered thermometer."
|
| Reminds me of the electronics adage: "all sensors are temperature
| sensors, some measure other things as well."
| Marthinwurer wrote:
| 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.
| emptiestplace wrote:
| https://en.m.wikipedia.org/wiki/Inertial_measurement_unit
| adolph wrote:
| Slight correction, latitude, not longitude.
|
| The earth's surface closer to the poles has less distance to
| travel for any rotation than the surface closer to the
| equator. As a result the inertial navigation systems of long
| distance systems must be adjusted. Iirc, this is also the
| case for artillery firing computations.
|
| https://www.oxts.com/blog/going-round-circles-earth-
| rotation...
|
| https://www.britannica.com/science/latitude
| billyjmc wrote:
| Coriolis corrections are thrown into sniper ballistic
| calculations, too. Not a huge effect in most conditions,
| but not zero, and there have been a lot of long shots in
| the past two decades.
| psunavy03 wrote:
| "Oi! Suzy!"
| 01HNNWZ0MV43FF wrote:
| Is that the same thing where a flat-earther tried to measure
| something with an expensive laser gyro and kept finding that
| Earth was rotating?
| adolph wrote:
| I think the most you can tell from an IMU or gyro is that
| there is a change in velocity in a direction aligning with
| East-West when there is a change in location and that the
| change in velocity is greater when the location changes in
| line with North-South. The change in velocity would be
| greater as one approaches the poles and lesser at the
| equator.
|
| Thought experiment: if I zeroed my IMU at the North pole
| and traveled in a straight line away from the pole along
| longitude zero, following the guidance of the IMU. By the
| time I got to 45deg latitude I'd be traveling Westward at
| 1,180 kph (.95 Mach) to keep the IMU at zero.
| trueshape wrote:
| The flat earther used a fibre optic gyro. You don't
| "zero" it, it continuously outputs a measurement of its
| own angular rate around it's sensitive axis. For a 3-axis
| gyro placed still on earth, it will read about 15
| degree/hour around wherever the axis of earth is
| oriented.
| nielsole wrote:
| Asahi Linux (and likely MacOS too) uses the resistance of the
| speakers coils to detect overheating of same speakers and
| reduces volume.
| psunavy03 wrote:
| 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.
| cushychicken wrote:
| > Reminds me of the electronics adage: "all sensors are
| temperature sensors, some measure other things as well."
|
| I wanna say that's a Bob Pease quote but I can't find an
| attribution to it.
| frankus wrote:
| I first encountered it in Elecia White's book Making Embedded
| Systems, but the attribution is anonymous and whom it's
| attributed to may have heard it elsewhere.
| user_7832 wrote:
| Is there one saying "All electronic devices are smoke machines,
| some can compute too"?
| frabert wrote:
| "All diodes are light-emitting if you try hard enough"
| gavinsyancey wrote:
| "All diodes are light-emitting at least once"
| dmoy wrote:
| Hahaha yea
|
| I've seen that in electronics lab a few times. The
| "temporarily light emitting diode"
| sitkack wrote:
| All diodes are also light SENSING is you try hard enough.
| immibis wrote:
| You don't have to try hard. Just use it as a photodiode
| and it magically works. However, if it's inside a plastic
| case that blocks light, it doesn't.
|
| Due to some law about entropy, efficient processes are
| necessarily reversible. That's why electric motors - some
| of the most efficient machines ever invented - are also
| generators.
| bsder wrote:
| Ah, the light emitting resistor. The moment when you
| realize why it's called Ohm's _Law_.
| jaggederest wrote:
| Similarly, diesel engines come with a reserve fuel supply
| that you can accidentally use once. (diesel engines will
| happily run on engine oil when warm)
| qingcharles wrote:
| "All electronics are hand-warmers if miscalibrated correctly
| enough."
| ChuckMcM wrote:
| "Inside every amplifier is an oscillator trying to get out."
| Bearsilber wrote:
| I just learned how the Duracell Powercheck(c) worked, which was
| done with temperature.
|
| https://youtu.be/zsA3X40nz9w?si=oGg2wdUlLXSDxpsN
| entropicdrifter wrote:
| It does act as a thermometer, if and only if the altitude
| remains constant. The speed of sound fluctuates with both
| temperature and altitude
| _0ffh wrote:
| Right, it gets even worse: Air pressure in not _only_
| altitude-dependent but fluctuates even at constant altitude.
| The pressure (altitude) dependence is comparatively weak,
| though.
| KeplerBoy wrote:
| one might say air pressure changes constantly as we speak.
| adammarples wrote:
| Isn't air pressure the only thing that microphones
| actually measure?
| sojsurf wrote:
| Air pressure differentials, to be precise!
| KeplerBoy wrote:
| 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 forms part of a capacitor and the electrical
| characteristics of capacitors depend on their geometry.
| jpc0 wrote:
| 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
| KeplerBoy wrote:
| 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
| jpc0 wrote:
| 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.
| sanderjd wrote:
| 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.
| immibis wrote:
| Many types measure the derivative of air pressure. One
| that measures absolute air pressure can be used for
| calibration.
| amluto wrote:
| 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 pretty good thermometer.
|
| https://en.wikipedia.org/wiki/Speed_of_sound
| pants2 wrote:
| In liquids the speed of sound is related to the density, I
| would have thought similar for air but I see your point.
| Very insightful!
| adolph wrote:
| Can an ideal gas of same volume, mass and temperature be
| brought to different pressures?
|
| https://courses.lumenlearning.com/suny-
| physics/chapter/13-3-...
| amluto wrote:
| Not unless you change the average mass of the molecules.
|
| An ideal gas' pressure is a function of number of
| particles per unit volume, its temperature, and nothing
| else. If you do anything involving adding or removing
| heat or _changing_ the volume or pressure, you probably
| also need to know the specific heat at constant volume
| and the specific heat at constant pressure or, frequency,
| their ratio. That ratio is called the adiabatic index or
| the heat capacity ratio, it's written as gamma, and it's
| the last parameter in the speed of sound of an ideal gas.
| Interestingly, it doesn't vary all that much between
| different gasses.
| kqr wrote:
| Oh yeah. I realised this the day I discovered my fancy digital
| SLR was a thermometer: https://entropicthoughts.com/does-my-
| dslr-have-dead-pixels
| djmips wrote:
| A lot of people like myself consider heat a form of light but
| I guess a photographer would be just thinking visible light.
| They say that about 50% of the sun's light emissions comes in
| the infrared frequencies.
| kqr wrote:
| That seems like a mistake since heat can transfer e.g. via
| contact without any electromagnetic emission. In fact, that
| is what I think happens with the sensor also, given that
| there is an IR filter in front of it.
|
| But I may misunderstand your comment.
| adamcharnock wrote:
| I would love to see this come to our various mobile devices in a
| nicely packaged form. I think part of what is holding back
| assistants, universal-translators, etc, is poor audio. Both
| reducing noise and being able to detect direction has a huge
| potential to help (I want to live-translate a group conversation
| around a dining table, for example).
|
| Firstly it would be great if my phone + headphones could combine
| the microphones to this end. But what if all phones in the
| immediate vicinity could cooperate to provide high quality
| directional audio? (Assuming privacy issues could be addressed).
| hatsunearu wrote:
| It's already kind of implemented.
| abecedarius wrote:
| For the hard of hearing like me the killer application would be
| live transcription in a noisy setting like a meetup or party,
| with source separation and grouping of speech from different
| speakers. Could be life-changing.
|
| (Android's Live Transcribe is very good now but doesn't even
| try to separate which words are from different speakers.)
| adolph wrote:
| * Automatic speech recognition (ASR) systems have progressed
| to the point where humans can interact with computing devices
| using speech. However, the distance between a device and the
| speaker will cause a loss in speech quality and therefore
| impact the effectiveness of ASR performance. As such, there
| is a greater need to have reliable voice capture for far-
| field speech recognition. The launch of Amazon Echo devices
| prompted the use of far-field ASR in the consumer electronics
| space, as it allows its users to interact with the device
| from several meters away by using microphone array processing
| techniques.*
|
| https://assets.amazon.science/da/c2/71f5f9fa49f585a4616e49d5.
| ..
| MVissers wrote:
| I believe modern macbook pro's already have multiple
| microphones that probably do some phase-array magic.
| gizajob wrote:
| What about a soundfield microphone? Does about the same thing and
| the electronics can be done in the analogue domain.
| radiowave wrote:
| At a rough guess from the audio samples, that array is
| producing an acceptance angle much narrower than any Soundfield
| mic is capable of. The noise source is only 45 degrees off-
| axis; I'd say any first-order microphone polar pattern (i.e.
| those a Soundfield mic is capable of) would capture more of the
| noise than is demonstrated here.
|
| Of course, you can improve on the rejection of off-axis sound
| by instead using a microphone with a more specialized polar
| patten (e.g. a shotgun mic), but then you lose the property of
| the pattern being steerable merely by signal processing.
|
| Lastly, such an array of dirt cheap pressure sensitive mic
| capsules with some clever computation behind them strikes me as
| the sort of thing you could throw Moore's law at, if you could
| justify the quantity. Whereas, Soundfield mics don't make much
| sense unless you're working with very precisely machined
| pressure-gradient capsules.
|
| Still, I get the feeling it'll be a while yet before this
| technique starts looking viable for audio production work, but
| it's very interesting.
| hinkley wrote:
| Boeing ginned up a spherical version of these and used it on 787
| prototypes to identify candidates for sound deadening material.
|
| Apparently in loud situations like airplanes, audio illusions can
| make a sound appear to come from a different spot than it really
| is. And when you have a weight budget for sound dampening
| material it matters if you hit the 80/20 sweet spot or not.
| jcims wrote:
| Look up acoustic cameras on YouTube, there are some pretty
| impressive demonstrations of their capability. This is one of the
| companies I've been watching for a while, but it looks like FLIR
| and some other big names are getting into it:
| https://www.youtube.com/@gfaitechgmbh
|
| The one use case that is both creepy and interesting to me is
| recording a public space and then after the fact 'zooming in' to
| conversations between individuals.
| pftburger wrote:
| I wonder if there is a meaningful limit to number of listening
| zones. I'm imagining a 3d grid of virtual mics in a space, each
| with an AI behind it
|
| Heck, train the model on the raw sensor data and you get the most
| awesome conference mics
| beambot wrote:
| Starting to see more & more of this with drones. In some cases,
| it's for military to detect drones nearby. In others, it's being
| used by drone delivery companies to detect other planes in the
| sky in a way that is cheaper, works in low-visibility, and
| doesn't use the same power requirements as radar.
| dchichkov wrote:
| I'm curious, why haven't you used TDM I2S microphones for your
| array and used PDM?
|
| I understand that ICS-52000 is a relatively low cost ($2/100pcs)
| and there are even breakout boards available with 4 microphones,
| which can be chained to 8 or 16, like
| https://www.cdiweb.com/datasheets/notwired/ds-nw-aud-ics5200...
|
| Then you can take Jetson (or any I2S capable hardware with DSP or
| GPU on it) and chain 16 microphones per I2S port. It would seem a
| lot easier to assemble and probgam, if comared to FPGA setup.
| djmips wrote:
| This has been on my to-do list since forever! Nice work Ben Wang.
| cma wrote:
| 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?
| markhahn wrote:
| 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.
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