Test Results of Acusis S Linear Beamforming Microphone Array with AEC

Hey everyone,

I spent the last two days testing my new Acusis S. It is a linear microphone array that offers Far-Field Beamforming and AEC and can be used with just a USB cable. It was absolutely plug-and-play on Raspbian Buster and Windows 10 (no driver install needed).

If you want, you can use the Audio Jack of Acusis S to get Automatic Echo Cancellation.

Here are my test results:

This is the product page:

Because of its cost (about 90 Euros), it will not be the right choice for everyone, but I am very happy with it. Digi-Key shipped it to me for free within 2 days (ordered on 22nd of December, received it on Christmas Eve in Germany).

Tell me what you think :slight_smile:


quite impressive results :+1:t2:

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If I had not spent so much on just audio equipment to test & trial I would prob buy an Acusis S just to test & trial :slight_smile:
Beamformers have a geometry that tells the algs how to process and the Acusis S is the only linear wall mount geometry I know of, so on a wall it should be about perfect or any vertical face.

Its always the same with loud background noise as there is a threshold anything can cope with due to pure simple physics.

I think the XMOS XVF3500 DSP is a model up from any of the other XMOS units you can get (Respeaker) and they have opted to buy in Phillips ‘BeClear Speech Enhancement’

I am confused by what you mean by the Acusis audio ouput as thought it from a quick read it has audio pass through which is sort of cool as my test & trial head is thinking does that mean I can get a mixer and add microphones in places of noise if I so wanted and the background noise problem is a thing of the past.
Being analogue there should be no latency or clock drift problems which you will get if carrying audio via IP or I2S loopbacks that other boards have.
Also with AEC where we do have software my tinkering would be wondering what would it sound like with a double helping if run in conjunction with the Acusis S.

I would have a lot to play with still with the Acusis S and its expensive for a microphone but not much more than others and I think it does have some clear advantages.

If you put mics far and add them to AEC then you have some far more resilient to noise a BoyaMM1 or even better its super cardioid MM1+ right at the noise source with the rear facing voice.

You are probably happy with what you have and don’t want any more wires and cables but because it does have audio passthrough you do have the option to capture and process noise.

With one of these you could make the wife disappear https://www.aliexpress.com/item/32966474568.html
So £15 for a mic and £7 for a mixer many a man would say the ability is value for money.
Input both the audio output of your soundcard with the input of the mic and AEC should process both.
You might have to do some tinkering with levels but thinking a mic on a TV, Hifi or Piano through AEC should work extremely well or it will negate the AEC but thinking it would work.

The only software I use successfully is SpeexDSP but it works because you must use the soundcard your playing and capturing on and so negates the possibility to mix in further noise channels.

PS found a 4 channel stereo https://www.aliexpress.com/item/32967843730.html
But that sort of thing or even if you have a mixer as things there do sound musical.

There is a lot to play with that board, did you download or was that just default?
Acusis S Configuration Tool (aconfig)

We’ve developed our own Acusis S config tool (aconfig) to allow us to easily tune XVF3500 parameters from a host computer. Please check out XMOS (https://www.xmos.ai/) and XCore forum (https://www.xcore.com/) for more help and details on the parameters available for XVF3500.
Downloads https://acusis.s3-us-west-1.amazonaws.com/aconfig_linux.tgz

aconfig --set BEAMWIDTH is a pretty cool feature

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Hey @rolyan_trauts,

Thank you for the detailed response. You are right, I talked about the audio passthrough of the Acusis S and I could definitely imagine passing the sounds captured by other microphones through it to have them eliminated. So thank you for the hardware recommendations :slight_smile:

I did not download anything. All the results are absolutely default settings of the Acusis S.

Yeah without actually trying myself I really don’t like to give untested recommendations but the Acusis S did seem the best for for your needs.
I did this with an Anker Powerconf and only reason I have one is because when the recommendation didn’t work well I purchased one to see if I could fix things.
The Anker works well with Windows but audio out seems to go to sleep and cut under linux.

You seem to have no problem with the Acusis S and it ran as stock which is great as if like the Beclear documemtation says (also a relief :slight_smile: ).

BeClear is the only solution currently on the market capable of full duplex, multi-channel echo cancellation.

It might work by mixing noise into the ‘near echo’ signal of the aec passthrough or it might need another input channel to be implemented but as far as I am aware nothing else comes close.
Its has audio passthrough for convenience but I think it just needs an analogue input of the ‘near noise’ that you can combine with far by mics and have as an AEC input but obviously don’t pass through to output audio.

You used it in a Magic mirror which is an amazingly good builders project that maybe if the Acusis S & Pi formed a soundbar it could form something truly awesome also.

Because of the strong synergy between Magic Mirror & Voice AI I have been a bit dismayed that a MagicMirror page selector isn’t a default intent GUI “Mirror mirror on the wall” and if not Mirror then next step soundbar.

Soundbar is that if it is the audio output for one of the biggest causes of noise for far field recognition (TV) it already embodies all the audio inputs for main noise cancelation where diversity of use can justify cost of some extremely cutting edge tech and not just cutting edge builders tech.

The extra software allow you to set a beamwidth which in specific cases you might want a specific catchment zone and restrict the beamwidth to less than 180 to escape likely noise.

Acusis S Configuration Tool (aconfig)
We’ve developed our own Acusis S config tool (aconfig) to allow us to easily tune XVF3500 parameters from a host computer.

If beamwidth is no interest then all is great as its totally plug&play.

https://www.digikey.co.uk/product-detail/en/antimatter-research-inc/AR-ACS1/2850-AR-ACS1-ND/13147322 its £20 more than the respeaker and I think you know I don’t like the expense of the array mics but because of the analogue pass through, better Xmos and likely Beclear algs if your going cutting edge its prob the one to go for.
You can do something similar with 2x soundcards for approx £20 that obviously lesser but either would be great and offer much more as a Rhasspy soundbar as noise is recognitions biggest problem.

Always a pleasure to read your detailed posts, @rolyan_trauts :smiley:

As we talked about in our private conversation, the Acusis S will be part of a Magic Mirror build to implement Rhasspy into it. Therefore I am very happy that you recommended it and that it fits so well for being mounted on a wall and all that without any driver installation or settings modification on the software side. The Phillips BeClear Speech Enhancement with full duplex, multi-channel echo cancellation really makes a difference (in comparison to my Matrix Voice which was about 70 Euros).

Your thoughts about integrating the Acusis S into a soundbar are very cool. It has the perfect form factor for such a use case.

Interesting device, thanks for posting the detailed testing.
Reading through thread this got me doing a quick search and I came across the “CrispMic II”. https://crispmic.com/crispmic-pcb/
Has anyone tried one?

It also looks interesting, but I’ve got a load of boards already that “looked interesting”… Matrix, ReSpeaker USB, Google AIY, ReSpeaker 2 mic hat, etc…

I’m really looking for something that can beamform based on the direction the wakeword arrived.

Now you said something of importance as without doubt the accuracy achievable by using known and trained wakeword to beamform to the direction of wakeword arrived is huge.

Crispmic needs to release more info about their product as things look a little less professional than Acusis and I am the same as have a useless Anker Powerconf a whole range of pointless Pi hats.
It would be great if you could give the Matrix a review and try to give a comparison to the Acusis as from what I am seeing it would seem to be the best of the bunch.
The matrix never seems to get a mention so haven’t a clue but heard very mixed reviews about the respeaker USB and then you get to the toys of Google AIY - 2 mic hats and they might as well just got a USB soundcard or a single I2S mic.

If Speechbrain do bring out https://speechbrain.github.io/ that touts ’ multi-microphone signal processing (e.g, beamforming)’ in a single toolkit that runs on the likes of a Pi its a huge gamechanger as we effectively will be able to train beamforming if we so choose.

I have been shouting this for a while but beamforming against physics with a singular room mic is always going to either need vastly more processing power or be less effective than simply using known keyword in a distributed conference array system.
That a base beamformer might be multiple instances of KWS 2x90, 3x60, 2x180 via directional mics.
That keyword confidence return is the channel metric and accuracy becomes a matter of trained models.

Without doubt though when it comes to the biggest problem of beamforming through interference patterns of noise the simple solution is not to do it and have locally near mics.
You might have 2x wireless KWS satellites running singular or multiple KWS/Mic instances at opposite ends of a room and opposite wall that is a basic config where KW confidence = voice near / noise far.

There is also https://distantspeechrecognition.sourceforge.io/ and my C and coding is very rusty and for me its a lot of work to test what the process load is as it does work.

I would say the Acusis S because it is very transparent in fact boasts a very good Xmos and Phillips Beclear alg usage that if you can afford then in terms of ‘dumb beamfrmers’ its the best we have seen.
Like all it can not be steered and is susceptible to noise whilst lower tech and cheaper solutions are not implemented.

The Respeaker USB is a decent far field mic. However, the beamform direction isn’t configurable from what I was able to tell. I was able to run through a few examples (over a year ago) and got DoA working, but without being able to set the direction of the beamform, it really only ever made the lights look cool.
That being said, out of the box if you use the audio out on the Respeaker, the AEC works great. I had Snapcast working and with music playing the mic would do a great job of isolating my voice. However the 3.5mm connections and an external speaker/amp wasn’t what I was hoping for.

The Matrix is also a pretty good far field mic, but for any of the audio tricks, it seems to all have to be done in software. I haven’t seen anyone get anything working with the DSP. If you look at the community, unfortunately it’s pretty dead. For DoA or Beamforming, they will typically refer to ODAS. https://github.com/introlab/odas
I was able to get it to run DoA using this tutorial and the results are pretty impressive, but the coding to make anything useful from all of it is above me.

Yeah I ran ODAS and can not remember if it was pi3/pi4 but had it running with the web app on my PC.
It was a sort of ‘Hmm’ thats great and boy that is a shed load of load.

WebRTC AEC actually has a direction input but none of it works in fact that is the weirdest thing about it as its locked from start and still doesn’t work or seem to do :slight_smile:

Singular beamforming is high load and extremely complex when KWS can run on $4 esp32 modules.
The Pi is a really odd fit at the moment as unless its going to host multiple instance KWS then its overpriced for distributed satellites and really falls far short of the needs of a centralised shared private service that collates usage and is self training.

I have been reasonably happy with a cheap Boya cardioid mic which seems to use a slightly bigger(14mm) and better quality unidirectional electret that el cheapo 9.7mm I have sourced.

All have the same problems of passing through predominant noise fields and the tech and cost just to use multiple placement is available and very cheap.

Thanks @RaspiManu & @rolyan_trauts for your discussion. I too have a collection of microphones at this point :sweat_smile: However, I went ahead and purchased an Acusis S on Saturday, which dispatched yesterday and will arrive tomorrow.

I have many satellites. Bedroom satellites are Pi Zeros with ReSpeaker 2 mics, conservatory is a Pi 3 with a ReSpeaker 4 mic. I initially bought the ReSpeakers as cheap and cheerful devices to test the viability of Snips and subsequently Rhasspy and simple matched the 2 & 4 to the form factor of the Pi. Fast forward and the ReSpeaker mics are still fine, because background noise in these rooms is low. I found the 2 mic to perform better than the 4s though, especially for the price, and have several 4s now gathering dust.

As for the living room, the most active room with the most background noise because of the TV, I found the ReSpeaker to be unsurprisingly poor. I purchased a Matrix Voice, which I’ve found to be better, but it would be amiss of me not to comment on the lack of development of the Matrix devices. Many of the promised features have not come to fruition, the community seems to be dead and I wonder if either Matrix is bankrupt, or they now only develop for private contracts/companies.

At the time I bought it I was aware of the missing features but there was still employee activity on their forums and development in progress - but that no longer seems to be the case - in retrospect it probably wasn’t a great purchase. Although our living room isn’t massive, it can be drowned out by the TV. I’ve written code to mute and pause the TV/ Roku/Shield upon hotword detection, but waking it in the first place isn’t guaranteed and overall, for the cost, I’d like it to perform better than it does.

The Acusis S seems to be a promising replacement to the Matrix Voice. I’d really like our living room environment to be more reliable and seemless than it is. Looking forward to trying it tomorrow!


I post this far too often but its a great bit of info if you sum channels of an array as the spacing and arrays of the 2 mic & 4 mic are fubar without beamforming algs.

The 2 mic for most parts is a broadside array that is only affected at the sides the 4 mic ends up as 2x broadside and is always affected if summed and likely better if you just use a single channel.

The Acusis looks really good and the reviews so far seem impressive but when it comes to noise beamforming just helps and depending on technology they are essentially just fancy directional microphones.
I think ODAS can do speaker Diarisation and if the Acusis could be steered that would also increase noise rejection but currently its likely it just focuses on the predominant audio signal and points that way and may not even provide VAD steering.
Probably does as presume the Philips BeClear software is a step up from the libs Xmos provide or Antimatter Research likely would not of purchased it.

The sensitivity to noise is also indicative of poor models and KW system and the problems of offering choice means we might not be talking of the same system or KWS.
I have been extremely bewildered with so much info with modern frameworks such as tensorflow, keras & pytorch that even a non programmer like me has assembled and run code examples that out perform what we have substantially.

The absence of provision to what is one of the easier models to provide has me waiting for external solutions as they could be provided but because they where not maybe elsewhere is a better option.
The distributed model and direction that has been chosen for opensource is essentially wrong as really we need a central system that trains via usage and not just black boxes provided my a singular person or entity.

That Acusis looks pretty amazing and without purchase still trying to work out how the audio passthrough works and if the BeClear multichannel function is part of the offering. (Someone explain USB audio in :slight_smile: )
Also in terms of feedback and direction of Antimatter Research can they improve on the software to allow dynamic steering & DOA feedback as not sure what the silicon is capable of.

But like I say microphone arrays without processing are fubar and singular directional mics are very valid and much more cost effective.
In fact you can have a directional array but a singular mic supplies the signal to a KWS instance otherwise just like omnidirectional when summed the effects can be detrimental.

The easiest way and still cheaper and more effective is multiple placement like professional conference wide distributed arrays where wifi technology is now so cheap it makes singular expensive beamformers a strange choice as they cost more and are inferior.

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Do you just want to know how the audio input from the Pi or PC works via USB, because the audio jack of the Acusis S is output only? When you connect the Acusis S with your system, you can choose it as Audio Input Device aswell as Audio Output Device. If you choose it for your system’s output, you can plug your speaker into the audio jack of the Acusis S. Hope this answers your question and I did not get it wrong :sweat_smile:

I know the Beclear has multichannel AEC but was wondering with the current if you mixed in a noise channel you don’t want it coming out of your audio out.
As you will have to input your audio out for AEC to work as I guess if audio input only then no AEC… ?

So way it is at the moment its Mic/Dac and the Dac signal is also used as the ‘noise’ for AEC removal.


Ok, now I understand what you were talking about. The standard AEC functionality works great when you send all the output over Acusis S to its audio jack and then remove the output audio waves from the audio input. You thought about sending background noise from other microphones to the Acusis S to filter it out via AEC, what would normally cause this microphone streams to come out of the connected speaker. I don’t know if you could configure the Acusis S to only output a special system audio stream and don’t output the others (background noise). It might be possible (maybe only with modifying the XMOS code), but I cannot answer your question, sorry.

Yeah it was just the Philips BeClear documentation that got me hoping the audio jack was in and connected to an ADC purely for AEC.
Then you can just split your output and also mix in, dunno why someone hasn’t had that idea but I don’t really have the rocket science degree that can work out why aec seems so sensitive to clock drift that the norm is to play and do aec via the dac.

The BeClear software can do multi-channel AEC but what you need for that I don’t know.
I might have a way to do it with a bit of alsa trickery and an additional sound card but its an off chance due latency matching that one time I will get round to testing.
Just surprised no system seems to of thought of a captured noise channel apart from high end conference equipment as presuming the DSP on that thing is far better than anything I can do with software.

Thanks for the replies as was curious but generally from what I hear impressed with the Acusis.


I received my Acusis S yesterday. I haven’t had a great deal of time to use it yet. In my limited testing so far I have to say it’s much more effortless in terms of being plug and play, and it’s performance than the ReSpeakers (drivers) & Matrix Voice. I moved around the house whispering intents from nearby rooms and it peformed admirably.

Having said that, I hooked it into my TV for AEC and found I could not wake Rhasspy on what I would say is my usual volume. I don’t yet know why, I haven’t yet investigated/analysed the recordings. Is AEC not working? Is the noise too great? Have I connected it incorrectly due to my tiredness last night? Is the default config not appropriate? Have I totally misunderstood how AEC works? All possible answers at this moment :sweat_smile:

Edit - I did look at the default configuration. From my brief play I found their software to interact with the microphone doesn’t work on a Pi. I had to hook plug it into my Windows laptop for a few moments to look at the configuration. Hopefully I won’t need to change too much…

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From what I can gather AEC on that unit is like any other and not sure how you could hook it up to a TV :slight_smile:
The usb in is an audio dac and should be the output of rhasspy and it uses that to attenuate that signal from the mic in.
The audio out jack should go to an amp.

The conf software from what I read is just selecting beam coverage so again guessing but if you did have a noise source you could make a narrower band?

Its weekend soon so hopefully you will have time to give it a trial.

I made the same experience when trying to play music via the Acusis S audio jack and record myself talking at the same time. The music or TV gets attenuated to a very low volume level in comparison to your recorded voice, but it seems that the AEC is mainly made for filtering another person talking out in a conference setting. This works like a charm. I had an online meeting with some friends and used the Acusis S and my soundbar for it. They never head themselves talking although I had them on a high volume. When trying to play loud music, my friends did hear it at a low volume level. The reason for this might be, that it’s focused on voice frequencies or that a talking person has less audio input than a song with 4 instruments and someone singing and it maybe does not have that much processing power, to filter it out.

What you could try is getting the wake word recognized and let Rhasspy lower the volume of the music or TV to get all the low volume sound cancelled out while talking. Cancelling low volume sound out is possible. I had some kind of success when I tried it. If you try this whole idea and get it working, please tell me about it :sweat_smile:

AEC the type we are using of from telephony days of hearing back your own voice with the delay of transmission wasn’t good.
AEC doesn’t attenuate noise that doesn’t go through the noise channel it passes through and the only noise channel it has currently is what it plays.
Like telephony the aec cancels its own voice as in what Rhasspy plays.

It uses Philips BeClear technology and yeah it focuses on voice.


Its really just a distance and clarity beast but noise is a killer of all, as the Acusis seems to be the king of current beamformers and I am really sorry but I have mentioned it so many times with the technology we have distributed mics where 1 can always be near and far from noise is the only solution.

Amazon & Google train KWS with noise and also noise suppression, part of the reason you have noise sensitive mics is that the KWS you use is noise sensitive.
Also another problem is choice of KWS in Rhasspy because in terms of accuracy some are OK and some are truly woeful and irrespective of that your comparisons mean nothing if your not using the same.
If you take the technology of say Raven its extremely easy to train and works well in a silent room but when it comes to error rate and noise there are reasons why no modern system elsewhere employs that type of basic audio recognition.
Precise as a name is probably an oxymoron and likely the worst thing in an opensource project the best performer is Porcupine and that is closed source.

So are hi-tech beamformers if fed into sub par KWS as until the model and audio processing chain is improved any mic in the presence of noise is likely to fail at fairly low thresholds.
You have an amazing mic far in excess of Amazon and Google units and the failure is due to what happens next with the signal.

One of the reasons I feel a soundbar is the best format for Rhasppy is that you can input the biggest sources of domestic noise TV & Hifi and play through Rhasspy as if you do connect noise channels to a unit it will absolutely trounce the like of google & amazon if we had the tensor cores they have in the cloud :slight_smile:

In the software config narrow the beam to a small radian and point away at far sources as bet its great fun but the technology of AI to decide what to point at is currently cutting edge with the likes of facebook https://github.com/facebookresearch/denoiser and https://www.nvidia.com/en-gb/geforce/guides/nvidia-rtx-voice-setup-guide/ and things like voice separation.

But in a domestic situation common noise sources are known so you purely capture at source and it doesn’t take AI to decide that.
I would really love to connect that mic you have to RTX Voice as an experiment but wow that is so far out of the reaches of my pockets but the mics you have are pretty damn amazing.

Hook your output up to an amp play some audio and then check how well the AEC is working.
The USB on the Mic is USB UAC1 and UAC2 which is 24-bit/192kHz and Windows only supports the lower class 1.