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Not really anything regarding stereo, but how to digitally recreate a 3D space and provide the resultant acoustic signature to stereo headphones? So, you could digitally model Carnegie Hall, or a warehouse, or a coffee shop, and if you know the locations of your point sources of audio you can then create what the room would sound like based on a given listener location and orientation? It sounds (a bit like) raytracing for audio, with the format allowing a standardized way to define the space.

Yes? No? For once, I think we actually need an *article* to go with this abstract, or at least a Bennet Haselton-style rant* as the summary.

*except factual, useful, and correct.

Kind of... You know how, even though you only have two ears, you can still determine whether a sound is coming from in front of you, behind you, above you, below you, etc.? You don't need 5 ears or 7 ears or whatever surround-sound standard you think of, and yet you still get a great 3D image. It has to do with some complicated math our brains are instinctively doing, measuring the interaural phase differences of low frequency signals received at each ear, and interaural timing and amplitude differences of high frequency signals. A signal from your right that gets to your right ear has to travel an additional foot and a half or so to get to your left ear, and that results in a phase difference for a signal with a long wavelength (say, below around 800 Hz) or a time and amplitude difference for signals with shorter wavelengths.
Additionally, your ears are not symmetrical, but have a small reflector at the front, a curved reflector along the top and back, etc., and these reflectors have specific reflective and absorptive bandwidths, so signals coming from different directions (above you, below you, etc.) are filtered in slightly different ways.

All of these features make up the head-related transfer function (HRTF) that acts as a filter on a signal based on its frequency and 3-dimensional position around your head.

As an aside, binaural recordings are typically done with things that look like headphones, but are actually microphones placed very close to the engineer's ears, so that the audio they pick up is affected by the HRTF. When you play the recording back over headphones, you get incredible 3D audio. And Neumann makes the KU 100 head-on-a-stick binaural microphone that actually has rubbery ears and microphones placed where eardrums would be.

This standard defines ways to store and process the HRTF so that recordings can be decoded by binaural processors for playback in earbuds or headphones. Importantly, it allows a recording to be stored in a format capable of multiple ways of decoding, so that you can have one track that you can play in surround sound from your speakers, or load up on your phone and play through ear buds, and still get a great 3D environment (binaural recordings don't work effectively through speakers, and surround sound collapses down to stereo through ear buds; this allows one file to play on both).

CCD's aren't digital and I'm not aware of anybody who thinks they are. People call cameras digital after the acquisition method, not the imaging device. Class D amps aren't digital amps either, we'd use DSP to adjust the amplitude of digital audio and not a pair of MOSFETs ;-)

> technically the speakers are playing "digital" sound.

Errm NO! Technically speaking the analog amplification stage is applied to a digital representation of an audio signal which is then converted into an analog signal at some point before the loudspeaker crossover.

There is no such thing as digital speakers, digital headphones or a digital microphone. Perhaps if Sen^H^H^HNeumann stopped lying about it people would take their so-called "digital mic" more seriously.

Re microphones: see the specs for the Neumann U87 (a classical high-end microhone) on the manufacturer's website:

• Neumann U87 historical scanned specifications (pdf): 20-16,000 Hz.
• Modern Neumann U87 Ai specifications: 20-20,000 Hz.

Apart from the technology, from psychoacoustic research it is known that frequencies above 16-18 kHz contribute extremely little to the listening experience, i.e., music with the range 18-22 kHz filtered out is for most people indistinguishable in double-blind tests from music with that range included. (Although it depends on whether the sound card is resampling the signal from 44 to 48 kHz, producing aliasing along the way) At least that is the picture I get from reading on hydrogenaudio.org.

Re microphones: see the specs for the Neumann U87 (a classical high-end microhone) on the manufacturer's website:

• Neumann U87 historical scanned specifications (pdf): 20-16,000 Hz.
• Modern Neumann U87 Ai specifications: 20-20,000 Hz.

Apart from the technology, from psychoacoustic research it is known that frequencies above 16-18 kHz contribute extremely little to the listening experience, i.e., music with the range 18-22 kHz filtered out is for most people indistinguishable in double-blind tests from music with that range included. (Although it depends on whether the sound card is resampling the signal from 44 to 48 kHz, producing aliasing along the way) At least that is the picture I get from reading on hydrogenaudio.org.

where do you get this crap.. the riaa website?

No, from musicians, animators, writers, directors, photographers, videographers, producers, label owners, and others that do business pretty much however they see fit - with, or without involvement with larger companies or industry associations.

They control the marketing

No, they control their own marketing. How am I prevented from running a Google ad, putting up fliers, shipping samples in conjunction with other businesses, using online distribution in ways I choose to create exposure, etc? How does a record label prevent me from doing that? I notice that you conveniently ignored, for example, the long list of independent labels I pointed you to. I know they sort of complicate your argument and might damage your rebel street cred, but you might want to look it over anyway. "They" don't control the marketing, they pay a lot for their own marketing. On the other hand, I've been turned onto all sorts of music I'd never have otherwise heard by subscribing to services like RadioIO. The artists that are showcased there have their CDs advertised, are paid for their airplay, and all based on the staff's appreciation of the quality of the music. Most of what they decide is worthy is vetted from recordings provided by the artists themselves. This is exactly contrary to your tinfoil-lined corporate conspiracy picture of the world. Buy a beer or two less this month, and try them out - you'll find that you're way, way wrong about many of your presumptions.

if one records off the radio, it has the same economic effect as downloading an mp3

No, because the musicians (if they want to be) are paid when the radio station uses their work as part of their day's business operations.

As far as human interaction is concerned you're damned right it's not

I'm thinking you have a typo, there. But would you consider talking to your mom on the phone not "real"? I'm not interacting with you face-to-face right now, any more than you are when you talk to family on the phone. What's your standard, lack of face time? What about when I'm talking to my wife in the next room, where I can't see her, but can hear her? In order to bolster your sense that the things you do online aren't "real," you're applying standards that show your own confusion about reality. Citing MMORPGs is ridiculous. That's not a bit different than people doing old fashioned play-by-mail, or four people sitting around a table playing paper-and-dice D&D. You're confusing communication mechanisms with anonymity, and assuming that anonymity washes away all requirements for respecting an artist's wishes.

You know about the costs of the OLD way of being a musician.

None of what I mentioned has ceased to be true. That you have a friend who put together a cheap studio doesn't change the laws of physics or change what it costs to make environments that have no EM hum, perfect acoustics, and clean power. Shopped for high-end condenser mics that will do justice to oversampled digital recordings of instruments with a huge dynamic range? You don't string up an entire percussion rig with Neumanns or studio-grade AKGs for a few hundred dollars. The pro-grade A-to-D converters that make the quality of recordings of which you're so interested in maintaining your fair use don't just cost a few hundred dollars. I have friends that have a copy of 3D Studio Max and various sorts of desktop renderers. All on hardware they built. They can even laboriously produce some pretty good looking output. But I also have a family member that works for Pixar, where they have to use thousands of machines to render the sort of output we all love to look at (and hear) in feature-length packages. Thousands of machines, managed by huge teams

Expensive studio mics reproduce the full range 20-20,000 Hz and leave it to the sound engineer to filter out high frequencies if necessary. Here's a real studio mic, a Neumann U89, -4 dB at 20 kHz (see PDFs under "Documents"). Good for about $3000. Or, an order of magnitude cheaper, Audio-Technica AT853a.

I sometimes use the latter type for making live recordings of chorus performances on minidisc and apparently, the white-noise background also extends to 20 kHz. It seems that the Atrac-compression (350 kbit/sec) has a hard time with the noise because you don't need golden ears to hear the compression artifacts.

More information about Neumann:

http://ei.cs.vt.edu/~history/VonNeumann.html
http://www.neumann.com/
http://www.mbi.ufl.edu/~vetneumann
http://www-gap.dcs.st-and.ac.uk/~history/Mathemati cians/Von_Neumann.html
http://www.math.columbia.edu/~neumann/
http://www.zyvex.com/nanotech/vonNeumann.html
http://www.karto.ethz.ch/neumann/
http://www.rit.edu/~drk4633/vonNeumann/
http://www.fsm-a.org/neumann

"Research"? Try "current product". Neumann, the top manufacturer of microphones in the world, has the KU 100 "Dummy head", with two fake rubber 'ears' and two microphones inside. This is known as stereo 'binaural' recording technique, and, through headphones, yields absolutely incredible 360 degree localization, including vertical displacement.

However, through speakers, it doesn't sound quite right, which is why it tends to only be used for specialized things.

-T

They also used a 40+ year old measurement microphone to calibrate it.

burris

Neumann, maker of *very* expensive, *very* high-quality studio microphones, has gotten on the horn with eBay a number of times and had auctions pulled, claiming trademark and copyright infringements. Do a search on eBay for "Neumann", and, chances are, a lot of the links you click will say "this auction is no longer in our database".

There's plenty of microphones up for auction on eBay right now and it's been that way for a while.

Neumann has no problems at all with people selling their microphones. In fact, you can go to the Neumann web site and post to their message board the serial number of an old Neumann microphone you are considering purchasing, and they will respond (publically) with the date of sale and who they sold it to (and any other information about the microphone they may have on file). Also, their engineers frequently give advice on how to evaluate an old condenser mic you are considering purchasing.

Go to this message where Stephan Peus, Neumann Director of Development, tells someone when each of two microphones they are considering purchasing were sold. Looks like they are pretty supportive of people buying their old microphones...

Neumann is quite proud of the fact that their microphones are so well made as to be useful and valuable even 50 years after manufacture. They don't do anything to impede this as it would reflect negatively an their well deserved reputation. The community that buys and uses these types of microphones is very small (professional recording engineers, artists, and specialist dealers) and Neumann knows it. They wouldn't piss those people off.

The ONLY time I have seen listings for Neumann mics pulled on eBay is because the lister broke other eBay rules such as adding to their listing discription ads with prices for other items that aren't being auctioned on eBay.

Burris