Hello Richard,
I was going to pipe up with very similar comments of my own... particularly as
my creative work often uses close mic material recorded with the Soundfield mic.
I've recently compared some of these close mic materials I've recorded with the
Soundfield and then transcoded to binaural via HRIR filters with 'in ear' close
mic binaural recorded material. Both sets of recordings sounded 'very near'.
Additionally, it isn't very difficulty to synthesise proximity in FOA and get
convincing results. See BLaH Appendix 2 (eqn 49):
E. Benjamin, R. Lee, and A. Heller, “Is My Decoder Ambisonic?,” in Proceedings
of the 125th Audio Engineering Society Convention, San Francisco, 2008.
There's some other things you can do with image spreading a la Gerzon to
increase the size of the image, too:
M. A. Gerzon, “Signal Processing for Simulating Realistic Stereo Images,”
Preprint 3423, 92nd Audio Engineering Society Convention, San Francisco, 1992.
Combining image spreading w/ proximity can give a convincing sense of nearness.
BTW, Andrés Cabrera has put together various spreading examples here:
A. Cabrera, “Pseudo-stereo Techniques: Csound Implementations,” CSOUND JOURNAL:
Issue 14, 02-Jan-2011. [Online]. Available:
http://www.csounds.com/journal/issue14/PseudoStereo.html. [Accessed:
24-Jan-2011].
--
J Anderson
On 21 Jul 2011, at 1:45 pm, Richard Lee wrote:
>> It is true that 1st order ambisonics doesn't consider distance, with all
> sources being reproduced at the distance of the speakers,
> .
>> synthesis, the ambisonic encoding equations do not include distance,
>
> Both of these are untrue.
>
> For the second, see the Appendix of BLaH3 "Is my decoder Ambisonic?" Heller
> et al, AES San Francisco, 2008
>
> There are two convenient proofs of the fallacy of the first.
>
> While making a normal recording, creep silently up to your TetraMic or
> Soundfield and whisper into it.
>
> When you play this back to an unsuspecting victim seated in the centre of a
> simple Classic Ambisonic rig, he will flinch. He certainly doesn't hear
> you at the radius of the speakers.
>
> The other 'proof' is the B-format motorcycle that Soundfield have played at
> nauseum at various shows. Ambisonic myth has it that this was recorded by
> the young Dr. Peter Lennox on Grand Vizier Malham's modified Calrec
> Soundfield Mk 3A while the Vizier was away on a diplomatic visit to the
> Great Turtle that Supports the Universe. This mike was one of the first to
> have IMHO, the proper EQ which allow a Soundfield to implement the correct
> Ambisonic Encoding Eqns in the Appendix of BLaH3.
>
> BTW, real human distance perception is TERRIBLE under anechoic conditions
> cos waveform curvature is about the only thing left. Those of you
> investigating distance perception, please take note.
>
> And you need a proper Classic Ambi decoder as defined by MAG and BLaH3 with
> NFC.
> _
>
> Why does this work?
>
> At LF, simple 1st order Ambisonics with NFC IS a wavefield / soundfield
> reconstruction system.
>
> Then there's the snake oil in Calrec Soundfields, hand squeezed from solid
> Unobtainium by Yorkshire virgins ... Shaddup Lee! Just Shaddup!
>
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