I remember in my earliest days in computer music, when I was at the
Electronic Music Studio in the Physics Department of University College,
Cardiff, having height effects on broadband sounds demonstrated to me by
Mike Greenhough of the audio research group (this was around 1970 so I
can't be completely certain what their research group's proper title used
to be). Anyway, he just moved a notch filter up and down from about 5 to
10kHz (iirc). Listening on headphones at least the perception of sources
moving up and down was very clear. Easy to try out, anyway.
Dave
On 11 December 2015 at 13:10, Augustine Leudar <augustineleu...@gmail.com>
wrote:
> Hi Bo,
> I googled "tinting" in relation to this but couldn't find any papers -
> could you point me in the direction of these demonstrations/links ? The
> thing is virtually all the HRTF info related to vertical localisation is
> above 4 khz. The device we made allowed you to move sounds up and down, and
> horizontally with a wii controller - it worked quite well but we did cheat
> a little by just making sounds more high pitched when they went upwards as
> well as convolving them with directional bands but this wouldn't work with
> all sounds.
>
> On 11 December 2015 at 12:54, Bo-Erik Sandholm <bosses...@gmail.com>
> wrote:
>
> > I just want to say that when I read Joseph's mail I feel like christmas
> has
> > come early this year :-)
> >
> > I have been thinking about headtracked binaural listening for a couple of
> > years and discussing it here and in other forums.
> >
> > The goal is to make it possible to listen to ambisonics first order with
> > earphones with head tracking usen open source programs and procedures.
> >
> >
> > I do not think we should wait until it is possible to create a individual
> > HRTF for a everey day nontechnical person.
> >
> > This is avaliable:
> > Software and hardware to do it with software written by
> > http://www.matthiaskronlachner.com/?p=2015 or the
> > Ambiexplorer on the phone with the same effort to build the head tracker
> > bu also t adding a blutooth transmitterand and using another firmware.
> >
> >
> > I have been thinking of taking another way to the goal.
> >
> > What I have been thinking of is a tinted head tracking binaural decoder
> (I
> > did not know the principle had a name)
> >
> > My take on the decoder is that it
> > - below ~ 4kHz it should use standard HRTF decoding and have a few
> > profiles selectable on the width of the head,
> > ignoring individual ear shape effects above 4kHz.
> >
> > - tinting used to improve the height perception in binaural decoding,
> > tinting subsituting for HRTF above 4kHz for height.
> > tinting has shown it is possible to add height information to
> > Stereo, This has been demonstrated.
> >
> > - I want the shoulder reflections to be taken in to account, I belive
> > the varying impact of a comb filter effect of the shoulder reflection is
> > VERY important.
> > - the software should be controlled by parameters for head
> > tilt related to shoulders and head versus body turning
> > - maybe also the normal distance from the ears to the
> > shoulders, but I do not think this is very important as we adjust to
> > clothes on shoulders very easily.
> >
> > I belive we should take inspiration from UNIX principles when creating
> the
> > software, that is to use a chain of software that each does one thing
> well
> > and do not have to be rewritten all the time, A number of VST modules
> that
> > can be chained for could be the solution.
> >
> > We already have a number of the needed modules, the advantage of modules
> is
> > that they can be replaced or switched between.
> >
> > - Ambisonic rotation and tilt controlled by OSC in VST - ambix_rotator
> for
> > example
> > - Binaural decoder, Ambix_binaural, Tinted binaural decoder - not
> > available
> > - Shoulder reflections - I believe the shoulders are in many cases left
> > out of the HRTF sets.
> > If not we work with the difference intoduced when turning the head in
> > relations to the fixed shoulders.
> >
> > Reaper DAW that I use is not free (shareware) but very low cost,
> >
> > Head tracking module,
> > http://www.rcgroups.com/forums/showthread.php?t=1677559
> > - I hope to get assistance to make two modifications to the firmware
> and
> > hardware,
> > the first is to change the output syntax of the data stream to OSC.
> > The second is to add a second 9DOF sensor on a cable and use this to
> > track shoulder movement.
> >
> > Best Regards
> > Bo-Erik Sandholm
> > Stockholm
> >
> > Amateur ambisonic recordist
> > Interest in sound reproduction since beginning of 1960's.
> > Ex Network Engineer and unix system manager
> > Not a Programmer now for 35 years :-)
> >
> >
> >
> >
> >
> >
> >
> > 2015-12-10 21:05 GMT+01:00 Joseph Anderson <
> > j.ander...@ambisonictoolkit.net>
> > :
> >
> > > I'd just add here that a sensible approach would be to use (or design)
> a
> > > 'tinted' decoder. That is, a decoder that includes frequency (& or
> time)
> > > domain filtering to color the soundfield on playback.
> > >
> > > Blue Ripple Sound <http://www.blueripplesound.com/> includes tinted
> > > decoders
> > > <http://www.blueripplesound.com/products/poa-decoding-vst> in their
> > > technology portfolio. (Furse describes this in a patent
> > > <http://www.google.com/patents/US20120014527>.) For the ATK
> > > <http://www.ambisonictoolkit.net/wiki/tiki-index.php>, I've thought
> > about
> > > including a help page in the SuperCollider documentation
> > > <http://doc.sccode.org/Browse.html#Libraries%3EAmbisonic%20Toolkit> on
> > how
> > > to go about implementing a tinted decoder, but haven't done so at this
> > > time.
> > >
> > > The basic idea of 'tinting' is very simple: process the reproduced
> > > soundfield in a way that 'enhances' or further achieves some effect
> you'd
> > > like. To enhance elevation, we may choose to color the soundfield in a
> > way
> > > that exaggerates this sense. We have two choices in the processing:
> > >
> > > 1. process the soundfield before decoding
> > > 2. process the soundfield after decoding
> > >
> > > A combination of both gives the most flexible results, and the best
> > choice
> > > really depends on what kind of decoding array you're working with. If
> you
> > > have a full 3D array, choice 2 makes sense. Whereas, with a 2D layout,
> > > processing the soundfield before decoding (option 1) is probably the
> best
> > > idea.
> > >
> > > Option 1 is implemented like this:
> > >
> > > - decode soundfield to array of equally distributed 'virtual
> > > loudspeakers'
> > > - filter 'virtual loudspeakers', depending on direction
> > > - re-encode soundfield
> > >
> > > Option 2 is this:
> > >
> > > - decode soundfield to array of real loudspeakers
> > > - filter these, depending on direction
> > >
> > > Choosing the correct filtering to enhance elevation is the tricky part.
> > > You'll want these to be phase matched. (Linear FIR, is an easy choice.
> > > Phase matched 2nd-order IIR shelfs also work well.) There are many
> papers
> > > about modeling HRTFs, a simple choice is to just review the suggested
> > > filtering for simple spherical head modeling. A very quick search turns
> > up
> > > a paper from Duda and Brown
> > > <http://www.ece.ucdavis.edu/cipic/files/2015/04/cipic_Brown_Duda98.pdf
> >.
> > > With listening in an Ambisonic soundfield, you need to remember that
> the
> > > listener's head already applies the listener's own HRTF. The trick will
> > be
> > > to enhance without unduly distorting.
> > >
> > > Something also useful to note: if you're a creative artist, you can
> > 'tint'
> > > the soundfield for creative purposes. A simple example is what might be
> > > what we call 'soundfield highlight'. The idea here is that we'd
> low-pass
> > > all of the soundfield, except our 'highlight'. And notably, we can
> steer
> > > where the 'highlight' is located. (E.g., highlight different parts of
> the
> > > soundfield.) We can think of this as 'directional masking', but with a
> > > frequency dependence. I won't go into the exact details of
> implementing a
> > > signal flow to generate this effect, but the ATK
> > > <http://www.ambisonictoolkit.net/wiki/tiki-index.php> includes all the
> > > parts needed to do so.
> > >
> > >
> > > My kind regards,
> > >
> > >
> > > *Joseph Anderson*
> > >
> > >
> > >
> > > *http://www.ambisonictoolkit.net/ <http://www.ambisonictoolkit.net/>*
> > >
> > >
> > > On Thu, Dec 10, 2015 at 9:29 AM, Jörn Nettingsmeier <
> > > netti...@stackingdwarves.net> wrote:
> > >
> > > > On 12/10/2015 04:59 PM, Peter Lennox wrote:
> > > >
> > > >> It does imply that an ambisonic panner plugin that incorporates
> > spectral
> > > >> manipulation would be more efficacious
> > > >>
> > > >
> > > > noooooo!
> > > >
> > > > if it's an ambisonic panner, it doesn't change the spectrum. if it
> > > changes
> > > > the spectrum, it's not an ambisonic panner :)
> > > >
> > > >
> > > >
> > > > --
> > > > Jörn Nettingsmeier
> > > > Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
> > > >
> > > > Meister für Veranstaltungstechnik (Bühne/Studio)
> > > > Tonmeister VDT
> > > >
> > > > http://stackingdwarves.net
> > > >
> > > > _______________________________________________
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> --
> www.augustineleudar.com
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--
As of 1st October 2012, I have retired from the University.
These are my own views and may or may not be shared by the University
Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK
'Ambisonics - Component Imaging for Audio'
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