[Sursound] Of stereo miking, Fourier analysis, and Ambisonics

2013-06-27 Thread JEFF SILBERMAN
I agree with your criticism, of course, but the demonstration is nonetheless 
instructive as it highlights the localization deficiencies of spaced techniques 
apart from the obvious other advantages. I readily acknowledge miking is a 
trade-off, but I fear that too few recordists fully appreciate the advantage of 
coherent localization NOT to spoil the listener's suspension of disbelief in 
the illusion of stereophony as do incoherent "spaced mono" techniques.



>
> From: Eric Carmichel 
>To: "sursound@music.vt.edu"  
>Sent: Thursday, June 27, 2013 4:33 PM
>Subject: [Sursound] Of stereo miking, Fourier analysis, and Ambisonics
> 
>
>Many thanks to everyone for your responses and insights (re Giving Precedence 
>to Ambisonics). I would like to comment on the following two responses:
>1. from Jeff
>**May I suggest “Demonstration of Stereo Microphone Techniques,” Performance 
>Recordings #6 wherein 18 coincident, near-coincident and spaced omni (2 and 3 
>mic) stereo techniques are compared via a line of loudspeakers mounted at 
>equal intervals and spanning 10 1/2 feet left-to-right. Each loudspeaker was 2 
>inches in diameter and the center to center spacing was 9 inches. An 
>electronically generated tick was switched to each loudspeaker in turn 
>starting at the center and moving full right, full left and full right again 
>before ending in the center. The pros and cons of each technique are 
>unmistakable...
>Jeff Silberman**
>and
>2. from J?rn
>**hi jeff,
>i think the test you're mentioning is not entirely fair, as much as i like 
>coincident techniques.
>such a setup tests for localisation only, and with wide-band transients it is 
>quite clear that spaced techniques will lose, and their main advantage (better 
>perceived spaciousness in stereo-only playback, and better LF response) is not 
>even considered.
>miking is a trade-off. testing individual aspects won't tell us much about 
>actual musical use.
>best,
>j?rn**
>
>Eric C. responds
>
>The array of 2-inch speakers is reminiscent of many psychoacoustical 
>experiments I’ve participated in: More laboratory-like than musical. Note that 
>the clicks run in a sequence in lieu of random places. Once we perceive a 
>pattern (e.g. L to R sequence), we begin to fill in the spaces based on 
>patterns. At least that’s my (intuitive) notion. Also, clicks are among the 
>easiest sounds to localize. The broadband nature of the clicks provides 
>multiple localization clues, to include ILD, ITD, and (very importantly) pinna 
>transfer cues. I have collected data from my personal lab to provide evidence 
>of this latter claim, and I welcome everyone to review and scrutinize it. 
>Listening tests were performed using 8 young, normal-hearing persons. A rather 
>large (2.6 MB) Excel spreadsheet contains all the data. I designed this 
>spreadsheet to provide descriptive statistics for any combination of listeners 
>(e.g., group all female participants), stimuli, listening
>condition (e.g., unoccluded), or azimuth/location on the fly. You can download 
>the Excel spreadsheet here (again, it's 2.6 MB):
>
>www.cochlearconcepts.com/stats/hearing_data.xls 
>
>Graphical representation of the results (using SPSS) are in the same folder, 
>and you can see it here:
>
>www.cochlearconcepts.com/stats/Figure_6_96dpi.jpg 
>
>As can be seen (and heard!), the broadband stimuli are easy to localize when 
>compared to tonal stimuli. When participants were donning binaural stereo 
>electronic earmuffs (net acoustic gain at ear = 0 dB, carefully calibrated to 
>match earcups), lateralization was accurate. But discerning front-back angles 
>on same side (L or R; e.g., 60 and 120 degrees) was nearly impossible. This 
>demonstrates what happens when ILDs and ITDs are preserved, but pinna cues are 
>lost. You can see spectral and time-domain analysis of the broadband stimuli 
>here:
>
>www.cochlearconcepts.com/stats/Figure_1_96dpi.jpg 
>
>I have to agree with J?rn that the example miking demonstration isn’t all that 
>fair, and for another reason: How much low-frequency energy can a 2-inch 
>speaker provide? Although the Fourier decomposition of a transient or *click* 
>sound may suggest it's a broadband signal, I have reservations about Fast 
>Fourier Transforms and clicks. My reservation is, in part, rooted in my own 
>ignorance of math, but I’ll have to state that I don’t believe the ear works 
>exactly as math would predict. Let me explain...
>Fourier series shows that an ideal impulse (Dirac delta function or Kronecker 
>delta?) can be decomposed into sine waves, but these waves have to begin in 
>the Paleozoic Era and end when travel to distance galaxies is a reality. 
&

[Sursound] Giving Precedence to Ambisonics

2013-06-27 Thread JEFF SILBERMAN
May I suggest "Demonstration of Stereo Microphone Techniques," Performance 
Recordings #6 wherein 18 coincident, near-coincident and spaced omni (2 and 3 
mic) stereo techniques are compared via a line of loudspeakers mounted at equal 
intervals and spanning 10 1/2 feet left-to-right. Each loudspeaker was 2 inches 
in diameter and the center to center spacing was 9 inches. An electronically 
generated tick was switched to each loudspeaker in turn starting at the center 
and moving full right, full left and full right again before ending in the 
center. The pros and cons of each technique are unmistakable...

Jeff Silberman



>
> From: Eric Carmichel 
>To: "sursound@music.vt.edu"  
>Sent: Wednesday, June 26, 2013 10:02 AM
>Subject: [Sursound] Giving Precedence to Ambisonics
> 
>
>Greetings All,
>I have a friend who's an advocate of the Decca Tree mic arrangement. Many of 
>his recordings (a lot of choir and guitar) sound quite nice, so I looked into 
>aspects of the Decca Tree technique. For those who may not be familiar, the 
>*traditional* Decca Tree arrangement is comprised of three spaced 
>omnidirectional mics. A center microphone is spaced slightly forward. From 
>what I've read thus far (Spatial Audio by Francis Rumsey, Focal 
>Press; and selected articles in the AES Stereophonic Techniques Anthology), 
>the slightly advanced time-of-arrival for the center mic stabilizes the 
>central image due the precedence effect. However, the existence of the third 
>(center) mic can result in exacerbated comb-filtering effects that can arise 
>with spaced pairs. So, to avoid these filtering effects, bring on a Soundfield 
>/ Ambisonic mic...??
>As I understand, Ambisonics already takes into consideration known 
>psychoacoustical principles, and is why shelving is used to *optimize* ILDs 
>and ITDs above and below 700 Hz, respectively. But as many readers may know, 
>there are some nearly unpredictable ILD/ITD effects at approx. 1.7 kHz (for 
>example, see Mills, 1972, Foundations of Modern Auditory Theory). Creating a 
>virtual Decca Tree seems straightforward. To move the center channel, or a 
>virtual mic *forward* would require little more than offline processing. I 
>wonder whether anybody has tried the following: Slightly delay all channels 
>except the signal (or feeds) that make up the forward-most (central) channel. 
>Using an Ambisonic mic would eliminate combing effects. I realize a number of 
>Ambisonic plug-ins have built-in crossed-cardiod, Blumlein, and spaced omni 
>functions, but not sure I've seen any of them give *precedence* to the 
>precedence effect or Decca Tree arrangement.
>Two-channel playback (both convention and binaural) is here to stay for a 
>while, so optimizing Ambisonics for stereo is desirable to me. In fact, one of 
>my favorite recordings from the late 80s was made with the band (The Cowboy 
>Junkies) circled around a Calrec Soundfield mic. I've never heard whether the 
>Trinity Session recording was released in a surround format, or if the mic's 
>hardware decoder converted straight to stereo from the get go. That particular 
>recording made me aware of the Soundfield mic, though surround sound wasn't an 
>interest for me at that time.
>If anybody I had attempted the Decca Tree using an Ambisonic mic (even with 
>addition of a separate and forward omni mic), I'd be interested in knowing 
>what your experiences were.
>Many thanks for your time.
>Best,
>Eric C. (the C continues to remind readers that this post submitted by the 
>*off-the-cuff* Eric)
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[Sursound] Giving Precedence to Ambisonics

2013-06-27 Thread JEFF SILBERMAN
Your memory jives with mine though as I recall, the instruments did surround 
the Soundfield. The vocalist was not recorded directly; rather, her voice was 
amplified through a loudspeaker positioned in front of the Soundfield.

Jeff silberman

>
> From: Martin Leese 
>To: sursound@music.vt.edu 
>Sent: Wednesday, June 26, 2013 10:53 AM
>Subject: Re: [Sursound] Giving Precedence to Ambisonics
> 
>
>Eric Carmichel wrote:
>...
>>> Two-channel playback (both convention and binaural) is here to stay for a 
>>> while, so optimizing Ambisonics for stereo is desirable to me. In fact, one 
>>> of my favorite recordings from the late 80s was made with the band (The 
>>> Cowboy Junkies) circled around a Calrec Soundfield mic. I've never heard 
>>> whether the Trinity Session recording was released in a surround format, or 
>>> if the mic's hardware decoder converted straight to stereo from the get go.
>
>The Trinity Session is CD UHJ encoded, so
>can be decoded to surround sound using an
>Ambisonic UHJ decoder.  However, when you
>do this, the performers are (correctly) located
>in strange places.  This suggests that the UHJ
>was not intended to be decoded.  Instead,
>decode it using the Super Stereo mode.  This
>keeps the performers at the front where they
>"belong", while still surrounding the listener
>with the ambience of the Trinity Church.
>
>From memory, the recording engineer has
>said that the output from the Soundfield mic
>went straight into a UHJ encoder, and only two
>channels were recorded.  If true, this means
>that the recording can not exist in B-Format.
>
>Regards,
>Martin
>-- 
>Martin J Leese
>E-mail: martin.leese  stanfordalumni.org
>Web: http://members.tripod.com/martin_leese/
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[Sursound] Spatial music

2012-04-14 Thread JEFF SILBERMAN

Are things really that bad? I need to get out more often!  I'm thinking that 
the 99% own flatscreens by now. If a homebuilder is going to place an 
electrical outlet on the wall suitable for mounting a flatscreen, he might as 
well put in suitable-located outlets for in-wall loudspeakers as determined by 
the location of the flatscreen.  As rooms shrink in size and skrink in number, 
I foresee the "media room" as the hub of all internet, entertainment and 
telecommunications of the future.  Since living space will be at a premium, 
a wall-mounted flatscreen and in-wall loudspeakers will become all the more 
advantageous.
 

--- On Sat, 4/14/12, Ronald C.F. Antony  wrote:




On 14 Apr 2012, at 04:46, JEFF SILBERMAN  wrote:

> The solution lies in getting the home/spec builder industry to integrate 
> in-wall loudspeakers at pre-specified locations (including ceiling) in the 
> 21st century "media room" which room will become the new normal much like the 
> kitchen has certain de-facto features/standards which are now taken for 
> granted.  In the fullness of time, multichannel audio in the home ultimately 
> will prevail because it is the last frontier.

That suggestion may apply for the 1% of people, not for the 99%.

More than half the people in the US live what in Europe people would simply 
call a ghetto, and of the rest, a lot of people are on their way to descend 
into that level of "wealth", given that wages under the new union contracts are 
not sufficient to sustain what one would call a middle-class life style with 
secured retirement.

To stick to your kitchen mataphor: the 1% have custom cabinets, Sub-Zero 
refrigeration units, Wolf or some high-end European appliances. For the rest, a 
kitchen is simply a room with a sink, a super-cheap electric stove and a 
second-hand fridge. They also don't have a laundry room, they have to go to the 
Laudromat with their dirty clothes, and I'd venture to guess that people rather 
invest in their own washer and drier than into a media room of the 21st century.

For a technology to succeed, it can't just target those who lead the gilded 
life.

Ronald
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[Sursound] Spatial music

2012-04-13 Thread JEFF SILBERMAN
As an ST-250 B-format pantophonic practitioner of nearly 20 years, I yield to 
no one in my appreciation of FOA via a hexagon layout with a Cepiar decoder.  
That being said, the benefits of the 3 rear loudspeakers (i.e., localized 
applause and reverberation) do not compare with the benefits acheived by the 3 
front ones (i.e., soundstage envelopment and spaciousness)! Indeed, I 
would never replace my 3 front loudspeakers with a quadrilateral layout.  Why 
three-speaker stereophony never became an end in itself is a mystery to me. It 
is not nearly as financially and logistically burdensome as surround sound and 
yet its benefits are very tangible.

--- On Fri, 4/13/12, Robert Greene  wrote:


Surround could have had the same effect for music. It could have raised one's 
expectations of realism and made some kinds of music sound nearly right in a 
big way.  But for various reasons, it did not happen. For one thing, the pop 
music industry had moved into a realm where people no longer cared about the 
acoustics of the venue. "Music" became something that was not anchored in 
acoustic reality with a real venue.

But a lot of music is so anchored. And for that , surround done right is still 
valuable.

But done right is the operative phrase.

Robert
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[Sursound] Spatial music

2012-04-13 Thread JEFF SILBERMAN
The solution lies in getting the home/spec builder industry to integrate 
in-wall loudspeakers at pre-specified locations (including ceiling) in the 21st 
century "media room" which room will become the new normal much like the 
kitchen has certain de-facto features/standards which are now taken for 
granted.  In the fullness of time, multichannel audio in the home ultimately 
will prevail because it is the last frontier.

--- On Fri, 4/13/12, Gerard Lardner  wrote



I ain't objecting to HOA. I'd love to have a HOA system again for normal
listening; I /have/ heard it and agree it is good. But two things argue
against it: 1.) Cost for a home installation. Despite what I wrote in an
earlier message today, it was hard work to assemble even 8 /good/
speakers cheaply. I got them for HOA, but I probably will not use them
for it, at least not for long, because 2) Having lots of speakers on one
room is not compatible with home harmony or with visual aesthetics.
Sadly, that is the killer.

Bandwidth, storage, processing power? Yes, they are all affordable now.
Now we need to find a solution to my point 2 above - and that is not an
Ambisonics problem!

In practice, Ambisonics is most useful as a production tool. Only a
dedicated few will use it in a home environment. Only when the speakers
can be effectively hidden from view without compromising the qualities
needed for Ambisonics and for serious music reproduction will it have
the potential to become part of the home system.
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[Sursound] Transient time differences

2012-04-02 Thread JEFF SILBERMAN

--- On Mon, 4/2/12, Eric Benjamin  wrote:

> Don't take this to mean that I don't like ORTF recordings. 
> I do like them.  The 
> best stereo recording that I have ever made was an ORTF
> recording. But then, I'm 
> not a very good recording engineer.  I think that one of
> the reasons that I like 
> ORTF is that it introduces an artificial spaciousness which
> may compensate for 
> the spaciousness that is lost in stereo reproduction.

I think you might find that this lost sense of spaciousness (IACC) is 
attributable to 60-degree stereophony.  Three-speaker stereophony (Trifield 
decoded) with the left/right loudspeakers subtending a 90 degree arc does not 
suffer from a lack of spaciousness thus obviating the need to create artificial 
spaciousness a la spaced-omnis in order to compensate for 60-degree stereophony.
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[Sursound] Transient time differences

2012-04-02 Thread JEFF SILBERMAN


--- On Mon, 4/2/12, Eric Benjamin  wrote:

> In subsequent thinking about his question it occurs to me
> that the plausibility, 
> not of the signals in the recording but of acoustic signals
> that enter the 
> listener's ears, is an important indicator of whether the
> listener finds the 
> reproduction to be realistic or not.  If our ears receive a
> large number of cues 
> that are wrong, or at least implausible, then the
> reproduction is unrealistic.

I would hasten to add visual cues as well. Seeing a small listening room and 
observing loudspeakers interferes with the creation of the illusion.  Listening 
in a pitch black room (no light whatsoever!), as silly as it may seem, is 
imperative to create the suspension of disbelief. Try it!
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