[Sursound] PhD position in acoustic signal processing at Chalmers

[Jens Ahrens]

Dear Sursounders,

The Division of Applied Acoustics at Chalmers University of Technology in 
Gothenburg, Sweden, is seeking a PhD student in the field of array signal 
processing. Please find the official advert at 
http://www.chalmers.se/en/about-chalmers/vacancies/Pages/default.aspx?rmpage=job&rmjob=4409
 .  

The position is part of a new EU project called Levitate, which aims at 
creating a volumetric display that uses levitating objects as pixels. 
Levitation as well as haptic feedback and audible sound will be achieved using 
high-intensity ultrasound.

The application deadline is November 30.

Greets,
Jens

-- 
Jens Ahrens
Division of Applied Acoustics
Chalmers University of Technology
412 96 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people.php?page=jensa

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Re: [Sursound] PhD position in acoustic signal processing at Chalmers

[Jens Ahrens]

Hi Muhammad,

Thanks for your interest in our work!

Yes, indeed. At some point, we are planning to hire a postdoc, too. As the 
project is still in the preparation phase, it’s not quite clear when exactly 
this is going to happen. We’re currently thinking of spring 2017 or so. 

I’ll keep you (and the rest of the world) posted!

Greets,
Jens



> On 12 Oct 2016, at 13:35, muhammad hafiz wan rosli 
>  wrote:
> 
> Greetings,
> 
> This is interesting research. Do you by any chance have any positions for
> post-doc?
> 
> Thanks!
> 
> Best,
> 
> Muhammad Hafiz Wan Rosli
> PhD Candidate
> Media Arts & Technology
> University of California
> Santa Barbara CA 93106 US
> 
> www.mat.ucsb.edu
> ________
> 
> 
> On Wed, Oct 12, 2016 at 4:31 AM, Jens Ahrens 
> wrote:
> 
>> Dear Sursounders,
>> 
>> The Division of Applied Acoustics at Chalmers University of Technology in
>> Gothenburg, Sweden, is seeking a PhD student in the field of array signal
>> processing. Please find the official advert at http://www.chalmers.se/en/
>> about-chalmers/vacancies/Pages/default.aspx?rmpage=job&rmjob=4409 .
>> 
>> The position is part of a new EU project called Levitate, which aims at
>> creating a volumetric display that uses levitating objects as pixels.
>> Levitation as well as haptic feedback and audible sound will be achieved
>> using high-intensity ultrasound.
>> 
>> The application deadline is November 30.
>> 
>> Greets,
>> Jens
>> 
>> --
>> Jens Ahrens
>> Division of Applied Acoustics
>> Chalmers University of Technology
>> 412 96 Gothenburg
>> Sweden
>> +46 (0)31 772 2210
>> http://www.ta.chalmers.se/people.php?page=jensa
>> 
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>> edit account or options, view archives and so on.
>> 
> -- next part --
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[Sursound] New MOOC "Communication Acoustics"

[Jens Ahrens]

Dear Sursounders,

I would like to draw your attention to a new MOOC on the topic of communication 
acoustics: https://www.edx.org/course/communication-acoustics-rwthx-ca101 The 
course is a collaboration of several academics based in Germany as well as 
myself. It is going to start on Dec. 5. There are chapters on (amongst other 
topics):

- Fundamentals of acoustics
- Room acoustics
- Anatomy and physiology of the human hearing system
- Psychoacoustics
- Speech acoustics
- A lot on spatial audio capture and presentation
- Psychoacoustics in product sound design
- Perceptual audio coding

The course is in English (please don’t mind our accent…). It is more of an 
introduction to the topic. I would therefore think that it is not so 
interesting for most of you but it might be so for your students. The course is 
actually part of the curriculum at most of the participating universities, and 
we’re having onsite written exams at 4 locations. This is also the reason why 
the course is so long (14 weeks). It had to fit into the academic schedule.

Greets,
Jens

-- 
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210

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[Sursound] MOOC "Communication Acoustics"

[Jens Ahrens]

Dear Sursounders,

We would like to draw your attention to the re-run of our MOOC on the topic of 
communication acoustics. We actually chose to divide it into two courses this 
time in order for the durations to be closer to what is common for MOOCs:

https://www.edx.org/course/fundamentals-communication-acoustics-rwthx-tumx-ca101-1x
   
https://www.edx.org/course/applications-communication-acoustics-rwthx-tumx-ca101-2x
 ​ 

The course is a collaboration of several academics based in Germany as well as 
myself. The "Fundamentals" course is going to start on Oct. 23. The courses 
take place back-to-back, which means that the "Applications" course is going to 
start on Dec. 04.

There are chapters on (amongst other topics):

- Fundamentals of acoustics
- Room acoustics
- Anatomy and physiology of the human hearing system
- Psychoacoustics
- Speech acoustics
- A lot on spatial audio capture and presentation
- Psychoacoustics in product sound design
- Perceptual audio coding

The course is in English (please don’t mind our accents...). It is more of an 
introduction to the topic. We would therefore think that it is not so 
interesting for most of you but it might be so for your students. The course is 
actually part of the curriculum at most of the participating universities, and 
we’re having onsite written exams at 4 locations. 

Best regards,
Jens

P.S. The term "communication acoustics" was coined by Jens Blauert 
(https://www.ruhr-uni-bochum.de/ika/mitarbeiter/blauert.htm). It comprises all 
subdomains of acoustics that are relevant for the communication between humans 
and between humans and machines. This is of course not an exclusive definition. 
You may choose yourself what acoustic signals are those that convey information 
to you.

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/  



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[Sursound] PhD student position in acoustic signal processing and spatial perception

[Jens Ahrens]

Dear Sursounders,

The Audio Technology Group at the Division of Applied Acoustics at Chalmers 
University of Technology in Gothenburg, Sweden, is seeking applicants for a PhD 
student position in acoustic signal processing and spatial auditory perception: 
http://www.chalmers.se/en/about-chalmers/vacancies/?rmpage=job&rmjob=5499 It’ll 
be a five-year employment at Chalmers including the typical benefits.

The project will be revolving around the binaural playback of spherical 
microphone arrays recordings.

Best regards,
Jens Ahrens

-- 
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/
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[Sursound] 2-part MOOC on "Communication Acoustics"

[Jens Ahrens]

Dear Sursounders,

We would like to draw your attention to the re-run of our 2-part MOOC on the 
topic of communication acoustics:

https://www.edx.org/course/fundamentals-of-communication-acoustics  
https://www.edx.org/course/applications-in-communication-acoustics ​ 

The first part “Fundamentals of Communication Acoustics” starts this Monday. 
The course is a collaboration of several academics based in Germany as well as 
Chalmers University of Technology in Sweden. The two courses take place 
back-to-back, which means that the "Applications" course is going to start on 
Dec. 03, 2018.

There are chapters on (amongst other topics):

- Fundamentals of acoustics
- Room acoustics
- Anatomy and physiology of the human hearing system
- Psychoacoustics
- Speech acoustics
- A lot on spatial audio capture and presentation
- Psychoacoustics in product sound design
- Perceptual audio coding

The course is in English (please don’t mind our accents…), and it is more of an 
introduction to the topic. We would therefore think that it is not so 
interesting for most of you but it might be so for your students. The course is 
actually part of the curriculum at most of the participating universities, and 
we’re having onsite written exams at 4 locations. 

Best regards,
Jens

P.S. The term "communication acoustics" was coined by Jens Blauert 
(https://www.ruhr-uni-bochum.de/ika/mitarbeiter/blauert.htm). It comprises all 
subdomains of acoustics that are relevant for the communication between humans 
and between humans and machines. This is of course not an exclusive definition. 
You may choose yourself what acoustic signals are those that convey information 
to you.

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/  
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[Sursound] Postdoc position in acoustic signal processing at Chalmers, Sweden

[Jens Ahrens]

Dear Sursounders,

The Division of Applied Acoustics at Chalmers University of Technology in 
Gothenburg, Sweden, is seeking a postdoc in the field of acoustic array signal 
processing. Please find the official advert at 
http://www.chalmers.se/en/about-chalmers/Working-at-Chalmers/Vacancies/Pages/default.aspx?rmpage=job&rmjob=7297.
  

The position is part of an EU-funded project called Levitate in which we’re 
creating a volumetric display that uses levitating objects as pixels. 
Levitation as well as haptic feedback and audible sound are achieved through 
high-intensity ultrasound. Here’s the project website with plenty of videos and 
other resources: https://www.levitateproject.org/ We’re particularly looking 
for someone to work on parametric audio, i.e., audible sound created from an 
ultrasonic carrier. 

The application deadline is 15 April, 2019. The start date is flexible, and the 
position is limited to 12 months.

Best regards,
Jens

-- 
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/ 

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[Sursound] 2-part MOOC on "Communication Acoustics" starting next week

[Jens Ahrens]

Dear Sursound List,

We would like to draw your attention to the re-run of our 2-part MOOC on the 
topic of communication acoustics:

https://www.edx.org/course/fundamentals-of-communication-acoustics-2
https://www.edx.org/course/applications-in-communication-acoustics-2​

The first part “Fundamentals of Communication Acoustics” starts this Monday. 
The course is a collaboration of several academics based in Germany as well as 
Chalmers University of Technology in Sweden. The two courses take place 
back-to-back, which means that the "Applications" course is going to start on 
Dec. 02, 2019.

There are chapters on (amongst other topics):

- Fundamentals of acoustics
- Room acoustics
- Anatomy and physiology of the human hearing system
- Psychoacoustics
- Speech acoustics
- A lot on spatial audio capture and presentation
- Psychoacoustics in product sound design
- Perceptual audio coding

The course is in English (please don’t mind our accents…), and it is more of an 
introduction to the topic. We would therefore think that it is not so 
interesting for most of you but it might be so for your students. The course is 
actually part of the curriculum at most of the participating universities, and 
we’re having onsite written exams at 4 locations. 

Best regards,
Jens

P.S. The term "communication acoustics" was coined by Jens Blauert 
(https://www.ruhr-uni-bochum.de/ika/mitarbeiter/blauert.htm). It comprises all 
subdomains of acoustics that are relevant for the communication between humans 
and between humans and machines. This is of course not an exclusive definition. 
You may choose yourself what acoustic signals are those that convey information 
to you.

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/  
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[Sursound] Public release of ReTiSAR (Real-Time Spherical Microphone Renderer for binaural reproduction)

[Jens Ahrens]

Hello everyone,

We’d like draw your attention to this Python implementation that we’ve been 
working on. It’s an implementation of real-time binaural rendering of signals 
from rigid-sphere microphone arrays. So far, it only supports head tracking 
along the azimuth, but there is more to come. 

If you follow the quickstart instructions, you will hear a binaural rendering 
of a (casual) Eigenmike recording.

 Sorry, we’ve only tested things on macOS so far. ---

ReTiSAR is the real time version of 
https://github.com/AppliedAcousticsChalmers/sound_field_analysis-py, which we 
used, for example, in

J. Ahrens, C. Andersson, “Perceptual evaluation of headphone 
auralization of rooms captured with spherical microphone arrays with respect to 
spaciousness and timbre,” in J. Acoust. Soc. Am. 145 (4), April 2019

Hannes Helmholz, the author of ReTiSAR, will have a paper at the upcoming IEEE 
ICASSP and Forum Acusticum in which he used it. 

There is certainly some overlap with the functionality of other existing 
implementations. ReTiSAR was our first attempt to write a heavy-processing 
application in Python. We were hoping to avoid some of the programming overhead 
that we have been facing in C++ with SoundScape Render 
(http://spatialaudio.net/ssr/). We are happy to conclude that Python together 
with the JACK Client for Python 
(https://github.com/spatialaudio/jackclient-python) is indeed a viable 
framework. We can’t clearly conclude on if or by how much Python makes it 
easier. 

Currently, ReTiSAR can render 12th order on an iMac Pro. In this case, we 
emulate the microphone signals by convolving a single-channel signal with the 
measured impulse responses of an according array from the Cologne dataset 
http://audiogroup.web.th-koeln.de/wdr_irc.html (we are not aware that a 
12th-order array exists; we don’t have one in any case). Note that 12th order 
corresponds to significantly more than 100 channels. Admittedly, ReTiSAR needs 
a long block length of 4096 samples or so for this, which makes the head 
tracking laggy. But it still does it without interrupts. Eigenmike recordings 
(4th order) can be rendered with a block length of a few hundred samples on a 
Macbook.

So, here is the first public version: 
https://github.com/AppliedAcousticsChalmers/ReTiSAR 

We would like to highlight (and thank for the fact!) that we received funding 
and other support from Facebook Reality Labs, particularly from Ravish Mehra, 
Philip Robinson, David Alon, and Sebastià Amengual Garí. 

Best regards,
Jens
 
-- 
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/ 

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[Sursound] PhD student position in acoustic signal processing

[Jens Ahrens]

Hello everyone,

The Audio Technology Group within the Division of Applied Acoustics at Chalmers 
University of Technology in Gothenburg, Sweden, is seeking applicants for a PhD 
student position in acoustic signal processing and spatial auditory perception: 
https://www.chalmers.se/en/about-chalmers/Working-at-Chalmers/Vacancies/Pages/default.aspx?rmpage=job&rmjob=8609
 It’ll be a four-year employment at Chalmers including the typical benefits.

The project is a collaboration with Facebook Reality Labs and will be revolving 
around the manipulation of abstract representations of spatial room impulse 
responses. The application scenario is reverberation for virtual and mixed 
reality. 

Best regards,
Jens Ahrens

-- 
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/
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[Sursound] Database of sound source directivities - call for contributions

[Jens Ahrens]

Hello everyone,

This post aims at anyone who has data on sound source directivity available. 

Stefan Bilbao of the University of Edinburgh and I published a paper at this 
past ICASSP on a method that allows for computing a complete spherical harmonic 
(SH) representation of a sound source directivity independent of how much (or 
how little) information on the directivity is available, i.e., independent of 
how many data points are available. In a nutshell, we impose the magnitude of 
the directivity that is known on a spherical surface around the source (which 
we term the “finite-distance signature”) onto a spherical carrier wave. There 
are no limits in terms of how much interpolation we involve as we’re using only 
the magnitudes. (We add a minimum phase in the end to design the time-domain 
structure of the directivity).

There is quite a bit of directivity data available as polar diagrams or other 
magnitude-only data or data that are available only in the horizontal plane and 
the like that do not allow for a complete conventional SH representation to be 
computed. We can now revive these old data and make them suitable for 
applications that require such complete SH representation (like FDTD 
simulations). 

--- Here’s the thing: We would like to avoid browsing papers and read magnitude 
directivities from polar plots with a ruler. We would rather like to ask all of 
you who have such data to submit them to us electronically. ---

We would then process the data and make them available online. Here’s a first 
outline of what this could look like: 
https://github.com/AppliedAcousticsChalmers/sound-source-directivities/ So far, 
the repository contains only those data that we used in the papers that we 
wrote about the method (so far, only the ICASSP one has been published, so 
please stay tuned!). There’s a loudspeaker, a singing voice, and a handful of 
musical instruments.

The long-term goal is that this repository can serve as a tool to help finding 
out what kind of data representation is most useful for what application. A 
complete SH representation can be a good starting point as it allows for any 
other representation to be computed. But we haven’t really understood yet what 
people do with directivities. We might end up concluding that some other 
representation is more useful. But we don’t know yet, and we’d like to 
contribute to resolving this question.

(Just to clarify, we are aware that formats like SOFA exist. We’d primarily 
want to know what we need to put into the SOFA file…)

Thanks for your support!

Best regards,
Jens

-- 
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/ 

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[Sursound] Binaural rendering of an Eigenmike recording

[Jens Ahrens]

Hello everyone,

… and another post from me. 

Here’s a quick 2-min video of what binaural rendering of an Eigenmike recording 
can sound like for those of you who haven’t heard this before: 
https://youtu.be/qcqeygqjxZ4 It’s 4th order rendered directly in the spherical 
harmonic domain (without a virtual discrete loudspeaker array). The rendering 
was done with ReTiSAR (https://github.com/AppliedAcousticsChalmers/ReTiSAR), 
which is generously funded by Facebook Reality Labs. 

Best regards,
Jens

-- 
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/ 

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Re: [Sursound] Binaural rendering of an Eigenmike recording

[Jens Ahrens]

ideo). As mentioned above, ReTiSAR comes together with an Eigenmike recording. 
(Note, though, that we have tested ReTiSAR on macOS only.)

Fernando wrote:

> Right and Left sounded less reverberated, although the distance does not seem 
> to change so much - and the tone quality was (seemed?) brighter.

The timbre differences can be well explained with the effects of order 
truncation. We don’t really know what it is that changes the perception of the 
reverb.

Best regards,
Jens

—
Here’s a few references on the order limitation. Some include propositions for 
mitigating its effect:

C. Hold, H. Gamper, V. Pulkki, N. Raghuvanshi, I. J. Tashev, “Improving 
Binaural Ambisonics Decodingby Spherical Harmonics Domain Tapering and 
ColorationCompensation,” presented at the International Conference on 
Acoustics, Speech and Signal Processing, vol. 2, pp. 261–265 (2019)

M. Zaunschirm, C. Schörkhuber, R. Höldrich,“Binaural rendering of Ambisonic 
signals by head-relatedimpulse response time alignment and a diffuseness 
constraint,” The Journal of the Acoustical Society of America,vol. 143, no. 6, 
pp. 3616–3627 (2018).

Z. Ben-Hur, F. Brinkmann, J. Sheaffer, S. Weinzierl, B. Rafaely, “Spectral 
equalization in binaural signals represented by order-truncated spherical 
harmonics,” The Journal of the Acoustical Society of America, vol.141, no. 6, 
pp. 4087–4096 (2017).

J. Ahrens, C. Andersson, “Perceptual evaluation of headphone auralization of 
rooms captured with spherical microphone arrays with respect to spaciousness 
and timbre,” Journal of the Acoustical Society of America, vol.145, no. April, 
pp. 2783–2794 (2019).



> On 22 May 2020, at 01:20, Jacob William Wolfe  wrote:
> 
> Wow. Perception of distance especially - he sounds directly in my ear when he 
> gets close. 
> 
> On 5/21/20, 6:04 PM, "Sursound on behalf of mgraves mstvp.com" 
>  wrote:
> 
>That's really good!
> 
>Michael Graves
>mgra...@mstvp.com
>o: (713) 861-4005
>c: (713) 201-1262
>sip:mgra...@mjg.onsip.com
> 
>-Original Message-
>From: Sursound  On Behalf Of Jens Ahrens
>Sent: Thursday, May 21, 2020 11:04 AM
>To: Sursound 
>Subject: [Sursound] Binaural rendering of an Eigenmike recording
> 
>Hello everyone,
> 
>… and another post from me. 
> 
>Here’s a quick 2-min video of what binaural rendering of an Eigenmike 
> recording can sound like for those of you who haven’t heard this before: 
> https://youtu.be/qcqeygqjxZ4 It’s 4th order rendered directly in the 
> spherical harmonic domain (without a virtual discrete loudspeaker array). The 
> rendering was done with ReTiSAR 
> (https://github.com/AppliedAcousticsChalmers/ReTiSAR), which is generously 
> funded by Facebook Reality Labs. 
> 
>Best regards,
>Jens
> 
>-- 
>Jens Ahrens
>Associate Professor
>Division of Applied Acoustics
>Chalmers University of Technology
>41296 Gothenburg
>Sweden
>+46 (0)31 772 2210
>http://www.ta.chalmers.se/people/jens-ahrens/ 
> 
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Re: [Sursound] Binaural rendering of an Eigenmike recording

[Jens Ahrens]

Hi Len,

Interesting! Are your recordings available online somewhere (and maybe an 
example rendering of them)? It would be interesting to compare them to the 
Eigenmike ones.

BTW, we decided to add our raw recording to the public ReTiSAR repository. Some 
time next week or so...

Best regards,
Jens



> On 22 May 2020, at 18:24, moskowitz  wrote:
> 
> Jens Ahrens  wrote: 
> 
>> Here?s a quick 2-min video of what binaural rendering of an Eigenmike 
>> recording can sound like for those of you who haven?t heard this before: 
>> https://youtu.be/qcqeygqjxZ4
> 
> Nicely done!
> 
> We've been doing this too with OctoMic.
> 
> We use SSA's aXRotate VST plugin along with the EDTracker Pro headtracker 
> (around $100). Importantly, it allows for SOFA HRTF files. That feeds a 
> binaural decoder.
> 
> For binaural decoding, we use the COMPASS|Binaural parametric decoder, SPARTA 
> ambiBIN and IEM BinauralDecoder.
> 
> For the Eigenmike em32, you may get even better results if you use Angelo 
> Farina's calibration files.
> 
> 
> Len Moskowitz (mosko...@core-sound.com)
> Core Sound LLC
> www.core-sound.com
> Home of OctoMic and TetraMic
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[Sursound] EURASIP - Special Issue on Data-Based Spatial Audio Processing, call for submissions

[Jens Ahrens]

Dear colleagues,

Maximo Cobos, Konrad Kowalczyk, Archontis Politis, and I are organizing a 
special issue of the EURASIP Journal on Audio, Speech, and Music Processing on 
"Data-Based Spatial Audio Processing". We would be more than pleased if you or 
a member of your research group would consider submitting a manuscript.

Find the call for papers here: 
https://asmp-eurasipjournals.springeropen.com/spatial-audio 

Please note that the range of topics is fairly broad. We don’t only target 
machine learning-related topics. Anything that builds on data is welcome!

The deadline will be March 31, 2021. We are looking forward to receiving your 
submissions!

Best regards,
Jens

-- 
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/ 

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[Sursound] 2-part MOOC on "Communication Acoustics" starts next week

[Jens Ahrens]

Dear Sursound List,

We would like to draw your attention to the annual re-run of our 2-part MOOC on 
the topic of communication acoustics:

https://www.edx.org/course/fundamentals-of-communication-acoustics
https://www.edx.org/course/applications-in-communication-acoustics​

The first part “Fundamentals of Communication Acoustics” starts this Monday. 
The course is a collaboration of several academics based in Germany as well as 
Chalmers University of Technology in Sweden. The two courses take place 
back-to-back, which means that the "Applications" course is going to start on 
Dec. 14, 2020.

There are chapters on (amongst other topics):

- Fundamentals of acoustics
- Room acoustics
- Anatomy and physiology of the human hearing system
- Psychoacoustics
- Speech acoustics
- A lot on spatial audio capture and presentation
- Psychoacoustics in product sound design
- Perceptual audio coding

The course is in English (please don’t mind our accents…), and it is more of an 
introduction to the topic. We would therefore think that it is not so 
interesting for most of you but it might be so for your students. The course is 
actually part of the curriculum at most of the participating universities, and 
we’re having onsite written exams at 4 locations. 

Best regards,
Jens

P.S. The term "communication acoustics" was coined by Jens Blauert 
(https://www.ruhr-uni-bochum.de/ika/mitarbeiter/blauert.htm). It comprises all 
subdomains of acoustics that are relevant for the communication between humans 
and between humans and machines. This is of course not an exclusive definition. 
You may choose yourself what acoustic signals are those that convey information 
to you.

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/  
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Re: [Sursound] EURASIP - Special Issue on Data-Based Spatial Audio Processing, call for submissions

[Jens Ahrens]

Dear colleagues,

This is a quick reminder of the special issue to which we invite you to submit 
a manuscript.

The deadline is March 31, 2021!

Best regards,
Jens


From: Sursound  on behalf of Jens Ahrens 

Sent: Thursday, August 27, 2020 9:26:58 AM
To: Sursound
Subject: [Sursound] EURASIP - Special Issue on Data-Based Spatial Audio 
Processing, call for submissions

Dear colleagues,

Maximo Cobos, Konrad Kowalczyk, Archontis Politis, and I are organizing a 
special issue of the EURASIP Journal on Audio, Speech, and Music Processing on 
"Data-Based Spatial Audio Processing". We would be more than pleased if you or 
a member of your research group would consider submitting a manuscript.

Find the call for papers here: 
https://asmp-eurasipjournals.springeropen.com/spatial-audio

Please note that the range of topics is fairly broad. We don’t only target 
machine learning-related topics. Anything that builds on data is welcome!

The deadline will be March 31, 2021. We are looking forward to receiving your 
submissions!

Best regards,
Jens

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
41296 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/

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Re: [Sursound] EURASIP - Special Issue on Data-Based Spatial Audio Processing, call for submissions

[Jens Ahrens]

Dear colleagues,

We would like to inform you that we’ve postponed the deadline to June 15, 2021!

Best regards,
Jens


> On 5 Feb 2021, at 14:30, Jens Ahrens  wrote:
> 
> Dear colleagues,
> 
> This is a quick reminder of the special issue to which we invite you to 
> submit a manuscript.
> 
> The deadline is March 31, 2021!
> 
> Best regards,
> Jens
> 
> ____
> From: Sursound  on behalf of Jens Ahrens 
> 
> Sent: Thursday, August 27, 2020 9:26:58 AM
> To: Sursound
> Subject: [Sursound] EURASIP - Special Issue on Data-Based Spatial Audio 
> Processing, call for submissions
> 
> Dear colleagues,
> 
> Maximo Cobos, Konrad Kowalczyk, Archontis Politis, and I are organizing a 
> special issue of the EURASIP Journal on Audio, Speech, and Music Processing 
> on "Data-Based Spatial Audio Processing". We would be more than pleased if 
> you or a member of your research group would consider submitting a manuscript.
> 
> Find the call for papers here: 
> https://asmp-eurasipjournals.springeropen.com/spatial-audio
> 
> Please note that the range of topics is fairly broad. We don’t only target 
> machine learning-related topics. Anything that builds on data is welcome!
> 
> The deadline will be March 31, 2021. We are looking forward to receiving your 
> submissions!
> 
> Best regards,
> Jens
> 
> --
> Jens Ahrens
> Associate Professor
> Division of Applied Acoustics
> Chalmers University of Technology
> 41296 Gothenburg
> Sweden
> +46 (0)31 772 2210
> http://www.ta.chalmers.se/people/jens-ahrens/
> 
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[Sursound] A 7th-order array with 16 microphones

[Jens Ahrens]

Hello everyone,

We would like to make you aware of the concept of equatorial microphone arrays, 
which use a spherical scattering body and microphones along the equator of that 
body. Here’s a 3-minute video of a binaural rendering of the signals from such 
array: https://youtu.be/95qDd13pVVY

Their main advantage over conventional spherical microphone arrays is the fact 
that they require only 2N+1 microphones for Nth spherical harmonic order 
(conventional arrays require (N+1)^2 microphones). The price to pay is the 
circumstance that the array does not capture the actual sound field but a 
horizontal projection of it. This poses the question of what it may sound like 
if the array captures sound that originates from outside of the horizontal 
plane?!?

The video is going to demonstrate this!

Best regards,
Jens

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
412 58 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/

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Re: [Sursound] A 7th-order array with 16 microphones

[Jens Ahrens]

Hi Fons,

I’m not sure if I understand your question correctly. I’ll do my best to be 
comprehensive so that my response covers what you are interested in:

For this type of array, the spatial aliasing frequency f_a is dependent on 
order N and radius R of the array in the exact same manner like with spherical 
microphone arrays (SMAs): N = (2 pi f_a / c) R

   N = 7
   R = 0.0875 m

So that

   f_a = 4.3 kHz

The lower end is limited by the radial filter gain that the user chooses. The 
radial filters are not the same like with SMAs, but they are very similar so 
that the limitations are the same. 

   0th and 1st order are available for all frequencies. 
   2nd order approx. above 200 Hz
   3rd order approx. above 500 Hz 
   etc.

I cannot comment on calibration requirements because we did calibrate the 
array… (Nor did we measure how well it was calibrated out-of-the-box.). I don’t 
actually think that there are any special requirements. As before, much of the 
physical limitations are qualitatively (and also quantitively) similar to SMAs. 

Best regards,
Jens




> On 1 Dec 2021, at 12:36, Fons Adriaensen  wrote:
> 
> On Wed, Dec 01, 2021 at 09:03:59AM +0000, Jens Ahrens wrote:
> 
>> Their main advantage over conventional spherical microphone arraysi
>> is the fact that they require only 2N+1 microphones for Nth spherical
>> harmonic order
> 
> For the microphone in the video, what is the usable frequency range
> for each order, taking into account required gain and calibration
> accuracy (for LF) and aliasing (for HF) ?
> 
> Ciao,
> 
> -- 
> FA
> 
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Re: [Sursound] A 7th-order array with 16 microphones

[Jens Ahrens]

Hi Marc,

Yes, as with SMAs, the aliasing frequency scales inversely with the radius.

But a small radius limits the low-frequency end: The smaller the radius is, the 
higher will be the frequencies above which a certain (higher) order can be 
deduced. The 0th order is always there. For an array with a very small radius 
the 1st order may only be available above a certain frequency (and up until the 
aliasing frequency) etc.

The radius of this particular prototype had a very different motivation:

We figured out that there existed only about half a dozen arrays in the world 
that use this equatorial layout, and all of them were experimental prototypes. 
The one that we used in the video was originally built for motion-tracked 
binaural where the array needs to have a radius similar to that of a human head 
so that a useful ITD is produced. Here are the details of the array: 
https://www2.ak.tu-berlin.de/~akgroup/ak_pub/abschlussarbeiten/2018/Fiedler_MasA.pdf
  Fortunately, this is indeed a size that allows for fitting all hardware into 
the scattering body.

It is certainly no coincidence that this same size works well also for SMAs 
that perform spherical harmonic decomposition for subsequent binaural 
rendering. Many authors concluded this. One author that I can remember off the 
top of my head is Benjamin Bernschütz. His PhD thesis contains a lot of 
information on this.

If it works well for SMAs, then it works well for EMAs!

It was indeed a bit of luck that we were able to get hold of a prototype that 
was ideal for our purposes. In the near future, we will look into how small the 
array can be before things break down.

Best regards,
Jens



On 1 Dec 2021, at 15:55, Marc Lavallée 
mailto:m...@hacklava.net>> wrote:

Le 2021-12-01 à 09 h 20, Jens Ahrens a écrit :
I’m not sure if I understand your question correctly. I’ll do my best to be 
comprehensive so that my response covers what you are interested in:

For this type of array, the spatial aliasing frequency f_a is dependent on 
order N and radius R of the array in the exact same manner like with spherical 
microphone arrays (SMAs): N = (2 pi f_a / c) R

   N = 7
   R = 0.0875 m

So that

   f_a = 4.3 kHz

With a  bit of algebra, f_a = c  N / ( R 2 pi ).
So a smaller radius for the sphere would improve f_a?
Was 0.0875 m chosen in order to embed some hardware?

Marc
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Re: [Sursound] A 7th-order array with 16 microphones

[Jens Ahrens]

Hi Fons,

I’m attaching Fig. 1 from the JASA article. Please refer to the article itself 
if the image does not get through. It compares the SMA radial filters with the 
EMA radial filters. Whenever the solid lines deviate from dashed ones of the 
same color, then the given order is not available at the frequency range where 
the deviation occurs. If I’m not misreading, then the 7th order is available 
somewhere between 2 kHz and 3 kHz and higher. Aliasing kicks in at around 4 
kHz-ish.

So, indeed, there is not much more than 7th order that can be squeezed out of 
an array of this radius.

Regarding the calibration: Sorry for the imprecise wording! I meant to say that 
we didn’t check if there was actually any mismatch between the microphones. 
(This means in turn that I can't tell in how far the method is sensitive to 
that. My guess is that it is not more or less sensitive than SMAs.)
The reason why I’m not worried is because the array passed the stress test: 
When recording sound sources at a distance of, say, a few meters or farther, 
the whole setup is rather forgiving. That means, for example, that one doesn’t 
need to be too precise in the modelling of the scattering off the microphone 
baffle etc. The critical case is very close sources. Recall that in the video, 
I’m as close as a few centimetres to the surface of the array. This triggers a 
lot of the high orders at low frequencies, and if there is something that is 
not ideal, then the low frequencies tend to go through the ceiling. We tested 
this with the array, and it behaved.

How would I be noticing if the microphone mismatch is above the tolerance level?

Best regards,
Jens



On 1 Dec 2021, at 17:47, Fons Adriaensen 
mailto:f...@linuxaudio.org>> wrote:

Hi Jens,

Thanks for your reply.

The lower end is limited by the radial filter gain that the user chooses.

The radial filters are not the same like with SMAs, but they are very similar 
so that the limitations are the same.

  0th and 1st order are available for all frequencies.
  2nd order approx. above 200 Hz
  3rd order approx. above 500 Hz
  etc.

It's the 'etc' I'm interested in...

The gain required at LF increases by 6 * order dB for each octave going
down, which in turn means that for a given maximum gain the LF limit
goes up with order. Which makes me wonder if for order > 4 anything
useful actually remains.

I cannot comment on calibration requirements because we did calibrate
the array… (Nor did we measure how well it was calibrated out-of-the-box.).

Does the 'nor' mean you did _not_ calibrate it ?

I don’t actually think that there are any special requirements.

There are.

The required gain (at LF) means that small differences in capsule
sensitivity are amplified as well, and this distorts the resulting
polar pattern.

The simplest possible example would be a first order component X
being produced from the difference of two omni capsule signals
A and B, so

 X = (A - B) * (1 + j (F0 / F))

where F0 will depend on the distance between the capsules.

Now if A has actually 1 dB more gain the difference signal becomes

 1.12 * A - B = (A - B) + (0.12 * A)

The second term, amplified by the filter for low F, will add
an omni component to X.

So the maximum gain that can be used depends not only on how
much noise can be tolerated, but also on the calibration
accuracy (and long term stability) of the capsule gains.


Ciao,

--
FA







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Re: [Sursound] A 7th-order array with 16 microphones

[Jens Ahrens]

Hi Fons, hi Nando,

Please excuse that I’m responding to both of you in the same mail. There is 
sufficient overlap in the matters to keep the thread from diverging.

@Fons: Thanks for the clarification! We will look into this.

@Nando: (The question was what the high orders contribute.)

It’s hard to tell how exactly the high orders contribute. One aspect is the 
interaural coherence that needs to be appropriate. The other main aspect is 
what I typically term the equalization: Below the aliasing frequency, things 
are fine anyway. Above the aliasing frequency, the spectral balance of the 
binaural signals tends to be more even the higher the orders are that are 
present. The deviations from the ideal spectral balance also tend to be less 
strongly dependent on the incidence angle of the sound if higher orders are 
present.

Much of the angle dependent deviations of the spectral balance can be 
mitigated, for example, by MagLS so that the perceptual difference between, 
say, 7th order and infinite order is small. I can’t tell if it gets any smaller 
with higher orders. My (informal) feeling is that somewhere between 5th and 
10th order is where the perceptual difference to the ground truth saturates, 
both in terms of equalization and the coherence.

Best regards,
Jens



> On 2 Dec 2021, at 11:20, Fons Adriaensen  wrote:
> 
> Hi Jens,
> 
>> I’m attaching Fig. 1 from the JASA article.
> 
> Nothing was attached (or it got lost...)
> 
>> If I’m not misreading, then the 7th order is available somewhere between
>> 2 kHz and 3 kHz and higher. Aliasing kicks in at around 4 kHz-ish.
> 
> So the question is if this small range (less than one octave) actually
> contributes anything useful.
> 
>> My guess is that it is not more or less sensitive than SMAs.
> 
> I'd agree.
> 
>> I’m as close as a few centimetres to the surface of the array. This
>> triggers a lot of the high orders at low frequencies, and if there
>> is something that is not ideal, then the low frequencies tend to go
>> through the ceiling. 
> 
> If they don't that could just be because their contribution at LF
> is filtered out anyway, e.g. if your A/B process includes high pass
> filters of an order at least one higher than the order of the
> component they act on.
> 
>> How would I be noticing if the microphone mismatch is above 
>> the tolerance level?
> 
> One way uncalibrated capsule gains will show up is that after
> binaural rendering you get significant ILD at LF, which should
> never happen except for very close sources.
> 
> This actually happened recently with a binaural rendering system
> I was working on. When the room sound (early reflections and
> reverb tail) was added, this resulted in excessive ILD at LF,
> and a perception of the room sound that was clearly biased to
> one side.
> 
> The room sound in this case was from a real room, measured using
> an SMA. Analysing these measurements revealed capsule gain errors
> up to +/-3 dB. When these were compensated for, the problem
> disappeared.
> 
> 
> You could just measure the B-format polars at LF, but that would
> require an anechoic room.
> 
> You could instead compute the theoretical capsule signals for a
> set of directions, apply some gain errors, send the result through
> your A/B process, and plot the result.
> 
> The only thing that mitigates this problem is statistics: with
> a high number of capsules contributing to each harmonic, errors
> tend to average out to some extent. 
> 
> Ciao,
> 
> -- 
> FA
> 
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Re: [Sursound] A 7th-order array with 16 microphones

[Jens Ahrens]

Hi Fernando,

Absolutely, I’m happy to make that recording available. Give me some time for 
that, I’ll need to adapt the implementation so that it outputs the ambisonics 
signals in a useable format. 

The thing is, though, that the room was very noisy when I made that recording 
so that I’d want to find better content that allows for a more critical 
evaluation. I’ll speak with the guys from the audio communication group at TU 
Berlin who built the array, which was initially meant for motion-tracked 
binaural. I think that they made proper recordings of classical music and the 
like. I’ll see in how far they can share those. I’ll then convert them to 
7th-order ambisonics.

Best regards,
Jens



> On 14 Dec 2021, at 23:19, Fernando Lopez-Lezcano  
> wrote:
> 
> On 12/7/21 2:15 PM, Sampo Syreeni wrote:
>> On 2021-12-02, eric benjamin wrote:
>>> I believe that Nando may have been thinking about reproduction with 
>>> loudspeaker arrays. He has a system with eight loudspeakers on the 
>>> horizontal plane, as do I. So good up to third order.
> 
> And I actually have access to a 56.8 system[*] (in our "Stage" small concert 
> hall), the main horizontal speaker ring is 20 speakers, so quite a bit more 
> potential spatial resolution than just 3rd order.
> 
>> What is interesting here, to me, is that sampling on the recording side, and 
>> reconstruction on the playback side by discrete speakers -- also an instance 
>> of sampling in space -- are not the same, and they deteriorate the 
>> reconstruction of the soundfield separately. Sampling in recording array and 
>> sampling in reconstruction array...I've never really seen them analyzed at 
>> the same time, in the same framework. It's always been so that we go to an 
>> intermediate domain, which is continuous, with a little bit of wobble 
>> angularly, in noise or gain figures, and then back the same way.
>> It's all whole and good, if you can assume independence in all of the errors 
>> on the way. But then, you can't: the above Swedish case which I've been 
>> arguing, *certainly* doesn't admit such symmetry or independence assumptions.
> 
> Yes, there will be errors created by both the capture process (encoding into 
> ambisonics), and by the imperfections of the playback environment, be it 
> binaural or plain old speaker arrays. The errors will be mixed together...
> 
>> So, the statistical asummptions which underlie e.g. Makita theory, and there 
>> Gerzon's, don't go through. In particular, since we're dealing with wave 
>> phenomena, there is interference to be contended with. That doesn't come 
>> through at *all* in statistical analysis, across 2D and 3D analyses; 3D 
>> coupling to a 2D sensor is *wildly* uneven, and if you have a box around the 
>> sensor, it can be shown that the sensor coupled with its idealized 
>> surroundings, can exhibit resonant modes which run off to an infinite 
>> degree, within an infinitely small degree, in angle. It will *always* be 
>> nasty, at the edge.
>>> But I actually have 24 full-range loudspeakers available. Would it be 
>>> advantageous to expand our systems to higher order?
>> When you have those, the next thing is, you need an anechoic chamber, and 
>> well-calibrated microphones. I mean, you have the machinery to launch 
>> physical signals, in 3D. Now you need measurement machinery to catch what 
>> you launched, and a silent space between which doesn't perturb your signals. 
>> Is it that not so? ;)
> 
> Yup. While an ideal environment is best, we can try to do some testing done 
> in less than ideal circumstances. Let's assume we have some "machinery" in 
> place (reasonable playback environment, reasonable capture tools).
> 
> The question (to me) is really: what do we actually measure once we have the 
> machinery in place? Are there objective criteria that can tell us what is 
> perceptually relevant?
> 
> I would love to have the original 7th order recording that started this 
> thread, so that it could be played in different systems and with different 
> orders (Jens?).
> 
> Or: we can build horizontal arrays (or 3d arrays, for that matter) with N 
> capsules, where N is an ever increasing number.
> 
> What is the number of capsules and encoded order at which it does not make 
> sense to keep adding capsules (and spherical harmonic components). What is 
> the point at which "the incremental perceptual improvement, if any, is very 
> small and does not justify increasing the number of capsules needed to 
> capture higher orders". I know this would not be a black and white hard 
> limit, of course...
> 
> -- Fernando
> 
> [*] https://ccrma.stanford.edu/~nando/publications/stage_grail_2019.pdf
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[Sursound] An ambisonic microphone array based on a pumpkin

[Jens Ahrens]

Hello everyone,

I have good news, and I have bad news.

The good news is that higher-order microphone arrays do not need to be 
spherical anymore. The bad news is that they decompose after a while: 
https://youtu.be/fY8rfushmwM

Greets,
Jens

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
412 58 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/

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[Sursound] And finally: a head-mounted ambisonic microphone array

[Jens Ahrens]

Hello again,

Here’s the grand finale of our end-of-the-year video trilogy: 
https://youtu.be/OPWCXFbOFxU

Some people were shaking their heads when I told them about the possibility of 
mounting a microphone array on a human head - or an augmented reality headset 
for that matter. Combining it with an outward-facing camera array on that same 
device could allow for pretty spectacular shots.

A human head is, of course, not the only conceivable object to mount the 
microphone array on. A panoramic camera array of any form factor could be just 
as interesting of a use case.

Best regards,
Jens

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
412 58 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/

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[Sursound] 2-year postdoc position in psychoacoustics

[Jens Ahrens]

Dear all,

I don’t want to miss out on the opportunity of posting this also here on 
Sursound:

We have a postdoc position to fill. The deadline of June 30 is approaching!

Here is a short summary of the planned work:

The planned project will investigate and evaluate supportive architectural 
auditory environments that exhibit different levels of interactivity. A 
supportive environment in this context is considered an environment that does 
either amplify the user’s current mood or guide the user into a desired, 
positive mood. Most of the planned research will be conducted in virtual 
environments whereby it is also conceivable to conduct parts of the work in the 
physical world.

Please find more information here:
https://www.chalmers.se/en/about-chalmers/Working-at-Chalmers/Vacancies/Pages/default.aspx?rmpage=job&rmjob=10494

We are looking forward to receiving your applications!

Best regards,
Jens

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
412 58 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/
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[Sursound] MATLAB scripts for ambisonic encoding of signals from equatorial microphone arrays

[Jens Ahrens]

Hello everyone,

You might remember this video that we posted about a year ago on the concept of 
what we term equatorial microphone arrays (which are composed of a spherical 
baffle with microphones along the equator) and the binaural rendering of 
signals from such arrays: https://youtu.be/95qDd13pVVY?t=58 Such a setup needs 
only 2N+1 microphones to produce an ambisonic representation of Nth order. The 
16-channel array from that video produces therefore 7th-order ambisonic signals.

We figured that it may not be obvious to everyone how the signal processing 
would need to be implemented to produce ambisonic signals that are compatible 
with software tools like SPARTA or the IEM Suite. This entails actually an 
intermediate real-valued circular harmonic decomposition and other stunts that 
are not obvious from the original publication (JASA, 2021).

We therefore provide MATLAB scripts that implement the ambisonic encoding of 
the raw microphone signals (and the subsequent binaural rendering, too, for 
that matter) here: 
https://github.com/AppliedAcousticsChalmers/ambisonic-encoding The raw 
microphone signals from the video are also included  as an example case as well 
as pre-rendered binaural signals and a Reaper project that allows you to 
experience the binaural rendering with head tracking if you happen to have a 
tracker available.

There is plenty of pdf documentation, too.

To be comprehensive, we also provide the whole spiel for conventional spherical 
microphone arrays.

Best regards,
Jens

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
412 58 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/

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[Sursound] Special session on Sound Field Synthesis at I3DA 2023

[Jens Ahrens]

Dear colleagues,

We are organizing a special session on “Sound Field Synthesis", as part of the 
I3DA conference (Immersive and 3D Audio: from Architecture to Automotive), 
which will take place in Bologna, Italy from 5th to 7th September 
(https://www.i3da2023.org<https://www.i3da2023.org/>).

The topics of interest include but are not limited to methods for synthesizing 
or reproducing sound fields over an extended area by means of loudspeaker 
arrays. Prominent examples for such methods are wave field synthesis and 
ambisonics. We will also be pleased to receive contributions on transaural 
audio presentation.

If you are interested, we invite you to submit an abstract 
(https://www.i3da2023.org/call-for-papers/).

The conference deadlines are :

- March 31, 2023: deadline for abstract submission
- April 7, 2023: notification of abstract acceptance
- June 15, 2023: deadline for full paper submission.

All papers will undergo peer review. The I3DA 2023 proceedings will be 
submitted to the IEEE for publication. The proceedings will also be indexed on 
Scopus and Web of Science.

If you have any questions do not hesitate to contact us. We look forward to 
seeing you in Bologna.

Best regards,
Jens

--
Jens Ahrens
Associate Professor
Division of Applied Acoustics
Chalmers University of Technology
412 58 Gothenburg
Sweden
+46 (0)31 772 2210
http://www.ta.chalmers.se/people/jens-ahrens/

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