Re: [Sursound] Naive question on MS and Ambisonics
Didn't Lauridsen propose and experiment with stereo playback done this way--with a mono signal in the center and a diffference signal produced by a edgeon mounted dipole? Robert On Wed, 22 May 2013, J?rn Nettingsmeier wrote: Hi Ray, On 05/22/2013 01:24 AM, revery wrote: Hello j?rn, Thinking about what you say here, is this working by having pure M from the front and S from 90 degrees to the side, effectively 'mixing' the M S signals in the air as they reach the ears/brain? (Maybe I'm thinking about this too much, my brain is hurting.) Maybe :) Think about it this way: MS is a subset of Ambisonics, effectively missing the front-back and up-down information. So we can use it as an Ambi mic: The Mid signal gets panned where I need it. The Side signal is then used to give it a bit of width. For a frontal source, it will be fed to the Y channel only. Note there is no pressure component W from this signal. The only slight complication is that your side signal is not coincident with the main microphone, so you have to watch out for your overall image. If so, is there significant distortion/corruption of the effect from the two ears receiving different variations of the M and S signals? There is no coloration other than what's inherent in Ambisonics. I realise that ear crosstalk effect is an issue with standard two speaker stereo as well, but the consequences with this kind of signal presentation seem to me to be quite different. As part of this, if the head turns say 45 degrees to the left, the ear difference would seem to be at a maximum, with the left ear receiving a significant amount of the opposite lobe of the figure 8 with little cancellation effect from the M in front. Perhaps this is all part of the plan?.? Like I said, there is no magic mixing in the air. Ear crosstalk is not an issue in Ambisonics - we try to recreate a sound field, and the head is in there like it would be in the original field at the concert. So "ear crosstalk" is very much part of the experience. What you will hear is pretty much a widened version of the M signal. It's not strictly orthodox, but it works, as long as you don't overdo it and you get your delays right. For a less confusing way of mixing MS spots into Ambisonics, you can render them to Left-Spot and Right-Spot with a conventional MS matrix, and then pan those individually. Because they are coincident, there will be no comb filter artefacts, no matter how close you pan them. The reason I treat the S signal separately is because I usually work in third order, so the M mic is pretty sharp, and the S mic is then fed to first order only. The problem with this kind of mixed-order hackery is that the sound might shift when you truncate orders on playback (if no 3rd order system is available), but I already have this problem: my main mic is a first-order tetrahedron anyways. So I just watch out for it while mixing and frequently cross-check at lower orders to arrive at a useful middle ground. Best, J?rn -- J?rn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 Meister f?r Veranstaltungstechnik (B?hne/Studio) Tonmeister VDT http://stackingdwarves.net ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] [allowed] Re: Recreating a 3d soundfield with lots of mics.....
Sorry! I read the wrong volume! RFH is actually 21,960. This gives critical distance ~ 7 meters. (not that this changes my basic point but just for the record) Robert On Wed, 22 May 2013, Robert Greene wrote: No. But the fact that a hall sounds anechoic or nearly so does not mean it is! To the extent that I could find out on line in a quick search, it seems that the reverb time was about 1.4 seconds. This is much too short to sound satisfactory and moreover the rise of RT in the bass was not much--this is something that makes a hall sound thin and cold(like Disney in LA-- there is a lot of reverb there, 2 sec time but it is unifomr with respect to frequency-- the thing sounds like a bad audio system) However, while this is surely too dry to be a good hall, such a reverb time will still lead to the reverberant sound field dominating the total energy received. One just has to back up a bit further before this happens--but it will still happen at all but extremely close locations. For a fixed volume, the critical distance(beyond which reverb is more than half the sound) varies reciprocally with the square root of the reverb time. If the hall had a reverb time of 2.8 seconds(super wet) then the critical distance would be changed only by a factor of 1.4. ALLL halls that are not open to the out of doors have a critical distance that is smaller than the distance to most audience locations. A quick seat of the pants calculation for RFH (volume 11,600 cu m, rt 1.4) gives that the critical distane is around 5.5 meters. Not that far! Beyond that distance, reverb field is more than direct arrival. Because of the precedence effect, the sound seems to come straight from the players. But if is an illusion! CF www.regonaudio.com "Records and Reality" The relevance to the live versus speaker demo is that at distance, the power response of the speaker dominates the scene--the specific radiation pattern is not so important in detail. Which is why the AR demos worked! (and presumably the Wharf. ones as well) Robert On Tue, 21 May 2013, David Pickett wrote: At 12:16 21-05-13, Robert Greene wrote: Even "dead" concert halls in the relative sense have a lot of reverberation. A really dead hall still has a 1 second reverberation time say and most of what you hear in the audience is still reverberant sound. Did you ever hear an orchestra playing in the RFH pre 1960??? David ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Adding stereo to monophonic audio
Hi I seem to remember reading a review of kit that could do this - and/or construct 5.1 from stereo - aimed at TV broadcasters. That was just a couple of years ago - not the inverse comb filter system that was sometimes (mis)used to convert mono to stereo in the early days of stereo records. Every Blessing Tony > -Original Message- > From: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu] On > Behalf Of Andrew Castiglione > Sent: 22 May 2013 17:49 > To: Surround Sound discussion group > Subject: [Sursound] Adding stereo to monophonic audio > > Interesting http://hackaday.com/2013/05/22/adding-stereo-to-monophonic- > audio/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Naive question on MS and Ambisonics
Hi Ray, On 05/22/2013 01:24 AM, revery wrote: Hello jörn, Thinking about what you say here, is this working by having pure M from the front and S from 90 degrees to the side, effectively 'mixing' the M S signals in the air as they reach the ears/brain? (Maybe I'm thinking about this too much, my brain is hurting.) Maybe :) Think about it this way: MS is a subset of Ambisonics, effectively missing the front-back and up-down information. So we can use it as an Ambi mic: The Mid signal gets panned where I need it. The Side signal is then used to give it a bit of width. For a frontal source, it will be fed to the Y channel only. Note there is no pressure component W from this signal. The only slight complication is that your side signal is not coincident with the main microphone, so you have to watch out for your overall image. If so, is there significant distortion/corruption of the effect from the two ears receiving different variations of the M and S signals? There is no coloration other than what's inherent in Ambisonics. I realise that ear crosstalk effect is an issue with standard two speaker stereo as well, but the consequences with this kind of signal presentation seem to me to be quite different. As part of this, if the head turns say 45 degrees to the left, the ear difference would seem to be at a maximum, with the left ear receiving a significant amount of the opposite lobe of the figure 8 with little cancellation effect from the M in front. Perhaps this is all part of the plan….? Like I said, there is no magic mixing in the air. Ear crosstalk is not an issue in Ambisonics - we try to recreate a sound field, and the head is in there like it would be in the original field at the concert. So "ear crosstalk" is very much part of the experience. What you will hear is pretty much a widened version of the M signal. It's not strictly orthodox, but it works, as long as you don't overdo it and you get your delays right. For a less confusing way of mixing MS spots into Ambisonics, you can render them to Left-Spot and Right-Spot with a conventional MS matrix, and then pan those individually. Because they are coincident, there will be no comb filter artefacts, no matter how close you pan them. The reason I treat the S signal separately is because I usually work in third order, so the M mic is pretty sharp, and the S mic is then fed to first order only. The problem with this kind of mixed-order hackery is that the sound might shift when you truncate orders on playback (if no 3rd order system is available), but I already have this problem: my main mic is a first-order tetrahedron anyways. So I just watch out for it while mixing and frequently cross-check at lower orders to arrive at a useful middle ground. Best, Jörn -- Jörn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 Meister für Veranstaltungstechnik (Bühne/Studio) Tonmeister VDT http://stackingdwarves.net ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] [allowed] Re: Recreating a 3d soundfield with lots of mics.....
No. But the fact that a hall sounds anechoic or nearly so does not mean it is! To the extent that I could find out on line in a quick search, it seems that the reverb time was about 1.4 seconds. This is much too short to sound satisfactory and moreover the rise of RT in the bass was not much--this is something that makes a hall sound thin and cold(like Disney in LA-- there is a lot of reverb there, 2 sec time but it is unifomr with respect to frequency-- the thing sounds like a bad audio system) However, while this is surely too dry to be a good hall, such a reverb time will still lead to the reverberant sound field dominating the total energy received. One just has to back up a bit further before this happens--but it will still happen at all but extremely close locations. For a fixed volume, the critical distance(beyond which reverb is more than half the sound) varies reciprocally with the square root of the reverb time. If the hall had a reverb time of 2.8 seconds(super wet) then the critical distance would be changed only by a factor of 1.4. ALLL halls that are not open to the out of doors have a critical distance that is smaller than the distance to most audience locations. A quick seat of the pants calculation for RFH (volume 11,600 cu m, rt 1.4) gives that the critical distane is around 5.5 meters. Not that far! Beyond that distance, reverb field is more than direct arrival. Because of the precedence effect, the sound seems to come straight from the players. But if is an illusion! CF www.regonaudio.com "Records and Reality" The relevance to the live versus speaker demo is that at distance, the power response of the speaker dominates the scene--the specific radiation pattern is not so important in detail. Which is why the AR demos worked! (and presumably the Wharf. ones as well) Robert On Tue, 21 May 2013, David Pickett wrote: At 12:16 21-05-13, Robert Greene wrote: Even "dead" concert halls in the relative sense have a lot of reverberation. A really dead hall still has a 1 second reverberation time say and most of what you hear in the audience is still reverberant sound. Did you ever hear an orchestra playing in the RFH pre 1960??? David ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Measurement, Analysis, and System Implementation of the Head-Related Transfer Function
http://people.ece.cornell.edu/land/courses/ece5030/FinalProjects/s2013/pmd68 _ecs227_hl577/pmd68_ecs227_hl577/index.html -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130522/76dfcc33/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Adding stereo to monophonic audio
Interesting http://hackaday.com/2013/05/22/adding-stereo-to-monophonic-audio/ -Original Message- From: Hack a Day [mailto:comment-re...@wordpress.com] Sent: Wednesday, May 22, 2013 8:00 AM Subject: [New post] Adding stereo to monophonic audio Post : Adding stereo to monophonic audio URL: http://hackaday.com/2013/05/22/adding-stereo-to-monophonic-audio/ Posted : May 22, 2013 at 8:00 am Author : Brian Benchoff Tags : binarual recording, binaural, head transfer function, recording, stereo Categories : digital audio hacks http://hackadaycom.files.wordpress.com/2013/05/board.jpg A lot of awesome stuff happened up in [Bruce Land]'s lab at Cornell this last semester. Three students - [Pat], [Ed], and [Hanna] put in hours of work to come up with a few algorithms that are able to simulate stereo audio with monophonic sound (http://people.ece.cornell.edu/land/courses/ece5030/FinalProjects/s2013/pmd68_ecs227_hl577/pmd68_ecs227_hl577/index.html) . It's enough work for three semesters of [Dr. Land]'s ECE 5030 class, and while it's impossible to truly appreciate this project with a YouTube video, we're assuming it's an awesome piece of work. The first part of the team's project was to gather data about how the human ear hears in 3D space. To do this, they mounted microphones in a team member's ear, sat them down on a rotating stool, and played a series of clicks. Tons of MATLAB later, the team had an average of how their team member's heads heard sound. Basically, they created an algorithm of how binaural recording (http://en.wikipedia.org/wiki/Binaural_recording) works. To prove their algorithm worked, the team took a piece of music, squashed it down to mono, and played it through an MSP430 microcontroller. With a good pair of headphones, they're able to virtually place the music in a stereo space. The video below covers the basics of their build but because of the limitations of [Bruce]'s camera and YouTube you won't be able to experience the team's virtual stereo for yourself. You can, however, put on a pair of headphones and listen to this (http://www.youtube.com/watch?v=IUDTlvagjJA) , a good example of what can be done with this sort of setup. Read more of this post (http://hackaday.com/2013/05/22/adding-stereo-to-monophonic-audio/#more-98294) ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
