Re: [Sursound] Advice on Setting up a Listening Room

[Michael Chapman]

> Thank you Michael and Richard. It's now beginning to make more practical
> sense to me!
>
> 1. Just out of interest, when you "upsample" to Third Order Ambisonics,
> does that mean simulating the missing information?

I suppose so, but there are people on this list who could give a better
verb than 'simulate' ...

> Is it possible to
> record directly in TOA?
>
Various expt'l and less so (see (?sp)Eigenmic) methods,
but the practical answer is "No it is not possible."

> 2. Richard, you mention using the TOA Harpex VST plugin to create full 3D
> 16 channel TOA. Excuse my ignorance, but does 16 channels equate to 16
> speakers? And does this equate to 16 different speaker positions? (e.g.
> placed on the surfaces of a dodecahedron, but not on the nodes).
>
Ambisonic B-format has (2n+1) channels for pantophony (2D) and ((n+1)^2)
channels for periphony (3D).
Thus Third Order Ambisonics (TOA) has ((3+1)^2) = 4^2 = 16 channels.

B-format (storage/distribution) is not D-format (speaker feeds).
B-format
--has the minimum number of channels (useful for storage/distribution)
--can be decoded to 'any' speaker configuration (again 'useful')

First order horizontal-only B-format has 3 channels.
You will need at least a square rig (4 speakers) to reproduce it. Many
would say it would be improved by using a hexagon (6).


> 3. Do I require Jack if I am using a Blue Ripple Sound filter?
>
Leave that to Richard ... but I doubt it (not least as BR works on
Windows;-)>

> 4. Are AmbDec and Rapture 3D Advanced equivalent?
>
Totally ... holding breath for polite correction from Richard ;-)>
Seriously, of course not !

> 5. Do the speakers feed directly into the Motu Traveler (or equivalent)?
> In other words, if I hypothetically wanted to use 16 speakers (as in
> question 2), would I need something capable of having more speakers
> attached?
>
You need a soundcard with 16 'outs'.
IIRC the Traveller has
8 normal analogue outs
2 headphone outs ('L&R')
2 EBU outs ('L&R')
8 ADAT outs
The first ten are analogue, so easy.
Decoding EBU, no idea.
ADAT can be done with a ?150 / ?200 euro box.

Other Motus, you'll have to do your own research.

Ditto other multichannel soundcards.

But _if_ your 'repertoire' is fixed then a couple of Waveplayers might be
a lot cheaper ???

However TOA will need >>16 speakers ...  (so if you are going down that
path (do you need TOA?)) then you will be chaining Motus ( 1.5 to 2K
budget?) or using some other soundcard (suspect at least as much) or
cheating with 3 Waveplayers (c.700).
(BTW, don't think anyone on here has chained Waveplayers, but that it is
possible was the anglo-german consensus of reading the manuals ... the
manufacturer does answer English emails ... )

Good luck,

M


> Thanks for clarifying things for me.
>
> PS Michael, thank you for your suggestion about getting in touch with
> Eric. I will look up his posts later today.
>
>
> On 9 Jun 2014, at 12:15, Richard Furse  wrote:
>
>>> -Original Message-
>>> From: Sursound [mailto:sursound-boun...@music.vt.edu] On Behalf Of
>>> Michael Chapman
>>> Sent: 08 June 2014 15:58
>>> To: Surround Sound discussion group
>>> Subject: Re: [Sursound] Advice on Setting up a Listening Room
>>>
>>> [...]
 4. I don't know whether I need to consider placing speakers above (and
 below) the horizontal plane for the purposes I described above. It
 would
 obviously be more realistic, but noticeably so? If so, how many?
>>> If you want 3-D you will have to.
>>>
>>> Minimum for first order is 8 in a cube.
>>> First order may not be precise enough for you.
>>> On the other hand with a TetraMic you will only get first order.
>>> However you can massage first order to higher order (?Harpex ... but
>>> IIRC
>>> only horizontal).
>>
>> There's now also the "TOA Harpex" VST plugin, which upsamples from first
>> order B-Format to full 3D 16-channel TOA.
>>
 7. I was planning on recording listening situations using a TetraMic.
 From
 what I understand, I would use something like a Motu 4Pre to get the
>>> sound
 into a MacBook Pro (although that all sounds not very portable),
>>> ?Tascam DR-680 Eight Channel Portable Digital Audio Recorder
>>> see the TetraMic site ...
>>>
 then use
 software such as Reaper with ambisonics plugins (Blue Ripple Sound?)
 to
 create sound files with the correct encoding on. But then I'm stuck�
 do I
 play those sound files through special software, or do I play them
 through
 something like iTunes?
>>>
>>> You need to decode them to speaker feeds
>>> IMHO on Mac, Fons' AmbDec is your friend.
>>>
>>> You can feed the output direct (via Jack) to your speakers ... or you
>>> can
>>> save it to a multi-channel file and play it back how you like.
>>> [...]
>>
>> To give you some more options: with our (Blue Ripple Sound's) VST
>> plugins you can produce (and play) speaker feeds using decoders inside
>> Reaper. You'd need "Rapture3D Advanced" for a non-standard/irregular

Re: [Sursound] Advice on Setting up a Listening Room

[Fons Adriaensen]

On Tue, Jun 10, 2014 at 07:40:14AM +0100, Curtis Alcock wrote:

> 1. Just out of interest, when you "upsample" to Third Order Ambisonics,
> does that mean simulating the missing information?

In a sense, yes. What happens is that the input signal is divided
in a large number of narrow frequency bands, and for each of these
the algorithm tries to find out the directions. Then each band is
panned to either to a set of discrete speakers or re-enconded in
TOA. The way is this works is by solving a set of equations that
describe how two sources are encoded into first order AMB. For more 
than two sources the equations become ambiguous - there is no unique
solution. The algorithm works well if you have one or two clearly
defined sources in each frequency band, but it fails in complex
ways in case this condition is not satisfied.

If your studio is to be used for hearing research you should 
probably ask yourself if you want this sort of processing - it
sort of 'interpretes' the spatial information in a way that
is not at all related to how our brains do it.

> Is it possible to record directly in TOA?

It is sort of possible using the 32-channel EigenMic and some
processing. But the resulting TOA is not complete: the higher
order signals have a rather limited frequency range. Which in
turn means that a normal decoder will not handle them correctly.
It is possible to correct for this up to some point, and in that
case this method can produce usable results. Some of my collegues
here used it to produce a TOA sounscape of the city of Parma last
year - the result is quite impressive.

Normally HOA is recorded by panning individual sources and adding
AMB encoded reverb or room acoustics.

> 2. Richard, you mention using the TOA Harpex VST plugin to create
> full 3D 16 channel TOA. Excuse my ignorance, but does 16 channels
> equate to 16 speakers?

You need more than 16 speakers for full 3D third order. Good layouts
(without preferred directions or gaps) have 20-25 speakers.

> 4. Are AmbDec and Rapture 3D Advanced equivalent?

As far as I know, no. Ambdec is a full-featured decoder app for 
(currently) up to 3rd order and 36 speakers. Full-featured means
dual-band and having near-field compensation. But it is *only* 
a decoder, you have to give it the decoding matrices - it will
not compute them for you. I can provide hand-optimised decoder
matrices for Ambdec users.

If I'm not mistaken 3D-Advanced includes code to compute decoding
matrices for any speaker layout. Note that computing these matrices
for arbitrary non-regular speaker layouts is still some form of
'black art'. There are a number of algorithms that can produce
reasonable results, but none of them produce optimal decoders.


Ciao,

-- 
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Re: [Sursound] Advice on Setting up a Listening Room

[Curtis Alcock]

Thanks for your replies, Fons.

> If your studio is to be used for hearing research you should 
> probably ask yourself if you want this sort of processing - it
> sort of 'interpretes' the spatial information in a way that
> is not at all related to how our brains do it.

Do you think it depend on the type of research? The purpose of the room is not 
to simulate how the brain works, but to simulate an auditory scene – in a way 
that the brain can then use "as if it were real".

So to put it another way, because someone in the room would be using their own 
brain to "interpret spatial information", the question is whether the TOA 
processing you describe above would clash at all with a person's own 
interpretation of spatial information – or would a person be able to interpret 
the sound "as if it was real" (allowing for the obvious absence of other 
sensory stimulus!). Or if it not "real", what would they be missing out on? 
What type of "false information" might TOA give them?

Leading on from this question, is it even (practically) possible to simulate a 
sound field that uses processing that is related to how our brains do it? If 
so, what type of processing should I be looking at?

My main purpose is to see how the combination of a person + hearing technology 
+ sound scene integrates in order to "accurately" (i.e. "results in the studio 
are predictive of performance in real life".) assess the combined performance 
in a way that is repeatable across people and technology, then use that 
information to adjust the parameters on the technology. As a lot of this 
technology is now making decisions based on spatial information (I'm not sure 
about distance, but certainly direction), it is important to surround a person 
(and the technology) with sound that is "close enough" to real life.

Also, would there be enough spatial (even if it's only "interpreted") 
information in a TOA set up to convince the hearing technology to change it's 
directional microphone polar plot to reduce the loudest noise source?

Michael mentioned possibly using "virtual microphones" for a localization test, 
rather than discrete speakers. Do you think such a test would be repeatable 
across different people using TOA, or from what you understand about brain vs 
AMB, does it be too variable or open to interpretation?


>> Is it possible to record directly in TOA?
> 
> Normally HOA is recorded by panning individual sources and adding
> AMB encoded reverb or room acoustics.

Does panning individual sources mean moving the microphone (in which case, you 
would be losing the transient nature of sound)? Or does it mean recording from 
several spots simultaneously (e.g. triangulating)?

>From what you're saying, then, whilst it is theoretically and technically 
>better to record in HOA, achieving consistent good results are difficult? And 
>so up-sampling is generally considered the norm?

> You need more than 16 speakers for full 3D third order. Good layouts
> (without preferred directions or gaps) have 20-25 speakers.

Does that mean constructing a dodecahedron with speakers positioned on the 
nodes? Is there a minimum room area size?

> There are a number of algorithms that can produce
> reasonable results, but none of them produce optimal decoders.

Does hand-optimised decoding produce more optimal results?


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Re: [Sursound] Advice on Setting up a Listening Room

[Fons Adriaensen]

On Tue, Jun 10, 2014 at 11:49:13AM +0100, Curtis Alcock wrote:
> Thanks for your replies, Fons.
> 
> > If your studio is to be used for hearing research you should 
> > probably ask yourself if you want this sort of processing - it
> > sort of 'interpretes' the spatial information in a way that
> > is not at all related to how our brains do it.
> 
> Do you think it depend on the type of research? The purpose of
> the room is not to simulate how the brain works, but to simulate
> an auditory scene – in a way that the brain can then use "as if
> it were real".

The result (of processing such as done by Harpex) will be a 'correct'
sound field, one that could exist as the result of having real sound
sources in the room. It does not present 'false information'. But the
question is if such a sound field is representative of real daily
life ones. These do not have the limitation of at most two directions 
per frequency band per time slice. Imagine a typical space which will
produce many early reflections and some amount of reverb.
How much this matters in your field of research I really don't know.
 
> Leading on from this question, is it even (practically) possible to
> simulate a sound field that uses processing that is related to how
> our brains do it? If so, what type of processing should I be looking at?

The purpose of the system (as far as I can see it) is to create or
reproduce the sound field, leaving the interpretation to the listener.
So there should not be any processing that tries to mimic psycho-
acoustic processes, e.g. by deciding what is important (perceptible)
or not. 

You could compare this to lossy encoding (e.g. mp3). Such algorithms
will remove the things that we won't hear and reduce the information
rate that way. What they do is based on psycho-acoustic criteria - 
critical bands and masking. Which means you shouldn't use mp3 encoded
signals if you're doing psycho-acousting research on critical bands
and masking. 

> My main purpose is to see how the combination of a person + hearing
> technology + sound scene integrates in order to "accurately" (i.e.
> "results in the studio are predictive of performance in real life".)
> assess the combined performance in a way that is repeatable across
> people and technology, then use that information to adjust the parameters
> on the technology. As a lot of this technology is now making decisions
> based on spatial information (I'm not sure about distance, but certainly
> direction), it is important to surround a person (and the technology) with
> sound that is "close enough" to real life.

TOA will produce a fairly accurate replica of real-life sound fields.

> Also, would there be enough spatial (even if it's only "interpreted")
> information in a TOA set up to convince the hearing technology to change
> it's directional microphone polar plot to reduce the loudest noise source?

For normal TOA this will be the case. I can't really confirm is that is
still true for 'upsampled' TOA. If the loudest noise source is a discrete
one (a single or at most two directions) things will work. In the other
case an upsampled TOA may not correctly reproduce it (even if it may sound
OK - that is an entirely different matter). 
 
> Michael mentioned possibly using "virtual microphones" for a localization
> test, rather than discrete speakers. Do you think such a test would be
> repeatable across different people using TOA, or from what you understand
> about brain vs AMB, does it be too variable or open to interpretation?

I don't understand what is meant by 'virtual micrphones instead of speakers'.
The outputs of an AMB decoder can be interpreted as coming from a 'virtual
microphone' having some polar pattern, but I don't see the relation.

> >> Is it possible to record directly in TOA?
> > 
> > Normally HOA is recorded by panning individual sources and adding
> > AMB encoded reverb or room acoustics.
> 
> Does panning individual sources mean moving the microphone (in which
> case, you would be losing the transient nature of sound)? Or does it
> mean recording from several spots simultaneously (e.g. triangulating)?

Neither. It's the same process as multitrack recording for stereo or 5.1.
You start with individual (mono) sources, each of them is sent through
an AMB panner and the outputs of those are summed on an AMB mixing bus.
The panner just distributes its input signal over all the channels of
the AMB bus in the right proportions that represent any particular 
direction (just as a stereo panner distributes the signal between L and R).
Each mono signal is also sent (with controllable gain and delay), to a
processor that adds room acoustics and reverb. The amplitude ratio of
direct sound and reverb, and their relative delay determine perceived
distance. 

> > You need more than 16 speakers for full 3D third order. Good layouts
> > (without preferred directions or gaps) have 20-25 speakers.
> 
> Does that mean constructing a dodecahedron with speakers positioned

Re: [Sursound] HELP: Any methods on producing 3D audio in stereo?

[Martin Leese]

YL wrote:

> Hi, there,
> I'm radio program producer and recently my boss asked me to think about how
> to produce 3D audio in stereo.

It is not clear to me what you hope to achieve;
more information would be helpful.  By
"produce 3D audio" do you mean full-sphere
surround sound, or horizontal-only surround
sound?  By "produce ... in stereo" do you
mean using only two speakers, or two
transmission channels and more than two
speakers?

For horizontal-only surround sound with two
transmission channels (and four to six
speakers) use UHJ-encoding.  However, this
will require a decoder in the listener's living
room.

Regards,
Martin
-- 
Martin J Leese
E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] HELP: Any methods on producing 3D audio in stereo?

[Dave Hunt]

Hi,

Linguistically it can be said that "stereo is 3D".  "Stereo"  has  
come to mean two loudspeakers with two separate 'independent' audio  
channels. "3D audio in stereo" is then most easily understood to mean  
"3D audio using two audio channels".


This then means binaural, and headphone listening, or some  
'transaural' technique using crosstalk cancellation to play a  
binaural recording over a pair of speakers. Binaural doesn't always  
work entirely, even using recordings made using your own ears and  
listening back with headphones through the same set of ears.


Its main advantage is that no real extra hardware or extra  
transmission channels are required than for normal "stereo".


As I assume you would be mixing several streams of audio together to  
make your programs you would need to encode each stream separately  
spatially, with one or more suitable encoded global reverbs to aid  
distance perception. You could encode to ambisonics (you'd probably  
need a decoder and 8 or more speakers, carefully set up, to hear this  
properly) then recode to binaural. Because binaural coding uses  
complex filtering to encode virtual speaker signals audio artifacts  
start to occur, the more audible the more virtual speakers.


The alternative is direct binaural encoding of each stream. This  
sounds better probably because the binaural filter is used on a per  
source basis rather than on all of them. There is then a problem of  
how to make a binaural reverb, possibly truly impossible as really  
there is only reverb which is heard binaurally. A compromise would be  
an ambisonics based reverb which was binaurally encoded, where the  
colouration would be more acceptable.


Other obvious cues as to distance are level (not effective on its  
own, especially without movement) and HF absorption ( only happens  
appreciably at fairly considerable distance, but useable for artistic  
effect).


There are some binaural plug-ins for DAWs around, but fewer for  
ambisonics which is much more dependent on the surround audio  
architecture of the DAW.


You could try my programs "3DAudioScape" and "3DAudioScape Binaural".  
The former is ambisonics which can be recoded to binaural, and the  
latter binaural with an ambisonic reverb engine. They are both demos,  
Mac only at present, muting every so often for about 4 seconds. I've  
tried to make them so you can load programming data from one into the  
other and produce acceptable results.


They're designed to work on the multiple outputs of a DAW.

They're at
http://www.3d-audioscape.com

Ciao,

Dave


On 10 Jun 2014, at 17:00, sursound-requ...@music.vt.edu wrote:


On 9 Jun 2014, at 1:05 am, 霖の <951343...@qq.com> wrote:


Hi, there,
I'm radio program producer and recently my boss asked me to think  
about how to produce 3D audio in stereo. I understand thus sounds  
ridiculous and can't be make out . But what i'm thinking is any  
way to make the audio work having clearly distance information and  
direction information? I tried to turning Ambisonics audio into  
binarual audio which have some feelings like that. However, I can  
not make it all the time when it comes to business production. Do  
you have any good methods? By recording、editing in DAW or by max  
patch, etc.


Thank you very much!
YL
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Re: [Sursound] Sursound Digest, Vol 71, Issue 8 Re: HELP: Any methods on producing 3D audio in stereo?

[????]

hi??there??
Thank you very much on producing 3D audio in stereo. some suggests me to using 
binaural or Ambisonics signal for industrial stereo applications, which , 
however, make a crosstalk cancellation system into this DSP so that listeners 
could get the right position information when playback binaural or Ambisonics 
signal from conventional stereo speakers. Thus sounds a good idea, indeed. 
Besides these method, are there any other straighter ways to produce spatial 
sound in stereo ? i.e, by stereo mixing/ recording techniques. 


Thank you very much!
YL




-- Original --
From:  "sursound-request";;
Date:  Wed, Jun 11, 2014 00:00 AM
To:  "sursound"; 

Subject:  Sursound Digest, Vol 71, Issue 8



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Today's Topics:

   1. Re: HELP: Any methods on producing 3D audio in stereo?
  (Joseph Anderson)
   2. Re: Advice on Setting up a Listening Room (Curtis Alcock)
   3. Re: Advice on Setting up a Listening Room (Michael Chapman)
   4. Re: Advice on Setting up a Listening Room (Fons Adriaensen)
   5. Re: Advice on Setting up a Listening Room (Curtis Alcock)
   6. Re: Advice on Setting up a Listening Room (Fons Adriaensen)


--

Message: 1
Date: Mon, 9 Jun 2014 10:30:40 -0700
From: Joseph Anderson 
To: Surround Sound discussion group 
Subject: Re: [Sursound] HELP: Any methods on producing 3D audio in
stereo?
Message-ID:
<75471496-86d8-4488-8f5a-a2e35c9e9...@ambisonictoolkit.net>
Content-Type: text/plain; charset="gb18030"

Hello YL,

For a straightforward "off the shelf" solution suitable for industrial 
applications, I'd suggest the Blue Ripple TOA suite:

http://www.blueripplesound.com/product-listings/pro-audio


IMV, at the moment Reaper is the most usable DAW for working with Ambisonics:

http://www.reaper.fm/



Hope this helps!



My kind regards,



Joseph Anderson

j.ander...@ambisonictoolkit.net
http://www.ambisonictoolkit.net




On 9 Jun 2014, at 1:05 am, ?? <951343...@qq.com> wrote:

> Hi, there, 
> I'm radio program producer and recently my boss asked me to think about how 
> to produce 3D audio in stereo. I understand thus sounds ridiculous and can't 
> be make out . But what i'm thinking is any way to make the audio work having 
> clearly distance information and direction information? I tried to turning 
> Ambisonics audio into binarual audio which have some feelings like that. 
> However, I can not make it all the time when it comes to business production. 
> Do you have any good methods? By recording?editing in DAW or by max patch, 
> etc.
> 
> Thank you very much!
> YL
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Message: 2
Date: Tue, 10 Jun 2014 07:40:14 +0100
From: Curtis Alcock 
To: Surround Sound discussion group 
Subject: Re: [Sursound] Advice on Setting up a Listening Room
Message-ID: <727617d5-0b30-427c-8514-a179a5b92...@tiscali.co.uk>
Content-Type: text/plain; charset=utf-8

Thank you Michael and Richard. It's now beginning to make more practical sense 
to me!

1. Just out of interest, when you "upsample" to Third Order Ambisonics, does 
that mean simulating the missing information? Is it possible to record directly 
in TOA?

2. Richard, you mention using the TOA Harpex VST plugin to create full 3D 16 
channel TOA. Excuse my ignorance, but does 16 channels equate to 16 spe