Re: [Sursound] Array for sound field recording and extend the sound image
Hi Tim, Indeed, SNR is poor at low frequencies for this sort of technique as it relies on the phase difference between the two capsules as produced by their separation. The separation can't be too large as once it gets over half a wavelength the phase starts wrapping around but this means that at low frequencies the difference is tiny and requires a lot of amplification (cf. the 6dB rise in response with frequency that someone else mentioned). This results in poor SNR and worsening susceptibility to capsule variances as the frequency goes down. If you can cope with the extra complexity, using more than one set of capsules with different spacings to cover different frequency ranges is a good idea... Dave On 9 January 2013 00:15, David Pickett d...@fugato.com wrote: At 11:54 08-01-13, Tim Collins wrote: You can make a velocity microphone by subtracting two closely spaced omnis. I seem to recall that Blumlein did this and also found that the s-n ratio was poor. David ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound -- As of 1st October 2012, I have retired from the University, so this disclaimer is redundant These are my own views and may or may not be shared by my employer Dave Malham Ex-Music Research Centre Department of Music The University of York Heslington York YO10 5DD UK 'Ambisonics - Component Imaging for Audio' ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
HI, the front-back reversals problem isn't peculiar to ambisonics - it can sometimes happen in real life (most often, though not always, in a symmetrical space) and is well known in the laboratory. It's really a subset of the 'cones of confusion' problem, which Batteau proposed that Pinnae effects help with, and Wallach proposed head movements help with - and I'd say you get best results with both. Since ambisonics, especially in lower orders, actually homogenises potential pinnae cues (eg using multiple sources to produce a simulation of a plane wave from a single source), then 'search behaviour' - small head movements to produce different sets of pinnae cues- works less well than for real environments; movements have to be grosser, and for longer. Higher orders help, some kind of processing for high frequencies (Harpex, for instance) might help. I've even cheated with this and used a precedent (about 7ms), bandwidth limited, amplitude limited, version of a target source simply routed into a single speaker - sort of an infinite order applied to transients. This last removes some of the actual reversals that you get ion a large array with off-centre listeners cheers Dr. Peter Lennox School of Technology, Faculty of Arts, Design and Technology University of Derby, UK e: p.len...@derby.ac.uk t: 01332 593155 -Original Message- From: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu] On Behalf Of Chenrilin Sent: 09 January 2013 03:29 To: sursound@music.vt.edu Cc: Zhangdeming Subject: Re: [Sursound] Array for sound field recording and extend the sound image Without more details, it hard to speculate about problems, but I'll note that subtracting the outputs of two omnis to get a fig-8 response will result in a frequency response that rises 6dB/octave with a 90 degree phase shift relative to the sum. Unless that is corrected, these signals are not suitable for B-format. I have checked my encoder, and definitely right as you said. I have just compensated for the magnitude and lost the phase modification. After modified, the location of audio is right and the sound image have been extended and much natural. But if the location of the sound is on the front of array, the listener cannot perceive clearly ・ whether the audio is in the front or on the back. I think it needs more processing, e.g. add ・ head tracking. If I have I have good result, I will share it with all. But it need more time since ・ I am not familiar with it：） ・ ・ Thanx very much for help from all of you. 华为技术有限公司 Huawei Technologies Co., Ltd. [Company_logo] Phone: Fax: Mobile: Email: 地址：深圳市龙岗区坂田华为基地 邮编：518129 Huawei Technologies Co., Ltd. Bantian, Longgang District,Shenzhen 518129, P.R.China http://www.huawei.com 本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁 止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中 的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130109/4a9de64c/attachment.html -- next part -- A non-text attachment was scrubbed... Name: image001.jpg Type: image/jpeg Size: 6737 bytes Desc: image001.jpg URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130109/4a9de64c/attachment.jpg ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound _ The University of Derby has a published policy regarding email and reserves the right to monitor email traffic. If you believe this email was sent to you in error, please notify the sender and delete this email. Please direct any concerns to info...@derby.ac.uk. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
An open paper on directional mics http://www.iwaenc.org/proceedings/2001/main/data/buck.pdf I had a idea that I could use 2 close mounted mics (o) for Upper frequency ranges and a longer distance between 2 additional elements (x) to have better signal to noise ratio for the lower frequency band, would that be practical? Then mix the 2 hi o and low x frequency signals. (x) (o)(o)(x) 4 omni mics for a figure of 8 pattern mic, maybe mounted on a plate according to I have seen a DIY differential mic based on the blumlein principle http://www.williamsonic.com/DipoleMic/index.html A advanced way of doing it:-) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2677264/ - Bo-Erik -Original Message- From: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu] On Behalf Of Tim Collins Sent: den 8 januari 2013 18:54 To: Surround Sound discussion group Subject: Re: [Sursound] Array for sound field recording and extend the sound image You can make a velocity microphone by subtracting two closely spaced omnis. I saw a paper on making ambisonic recordings like this a couple of years ago: http://www.aes.org/e-lib/browse.cfm?elib=15389 The problems, though, are spatial aliasing at high frequencies and lack of sensitivity at low frequencies. These would both need addressing in a practical system. Best wishes Tim Dr. Tim Collins Electronic, Electrical and Computer Engineering University of Birmingham Edgbaston, Birmingham, B15 2TT, UK www.eee.bham.ac.uk/collinst -Original Message- From: Mike Felton [mailto:mjfel...@gmail.com] Sent: 08 January 2013 00:21 To: Surround Sound discussion group Subject: Re: [Sursound] Array for sound field recording and extend the sound image The mics are omnis It might be stating the obvious here but how would you get ANY directional information out of four OMNI mics close together? :-) Surely to get a fig-8 response you need two CARDIODS back to back (one of which is polarity reversed obviously). Mike Felton ___ 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] Array for sound field recording and extend the sound image
Thanks very much. You are so kind. I will have a try as your suggestion. Best regards, Rilin Chen Do let us know with what results ! These type of problems are usually a learning experience for us all Best of luck, Michael ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
You can make a velocity microphone by subtracting two closely spaced omnis. I saw a paper on making ambisonic recordings like this a couple of years ago: http://www.aes.org/e-lib/browse.cfm?elib=15389 The problems, though, are spatial aliasing at high frequencies and lack of sensitivity at low frequencies. These would both need addressing in a practical system. Best wishes Tim Dr. Tim Collins Electronic, Electrical and Computer Engineering University of Birmingham Edgbaston, Birmingham, B15 2TT, UK www.eee.bham.ac.uk/collinst -Original Message- From: Mike Felton [mailto:mjfel...@gmail.com] Sent: 08 January 2013 00:21 To: Surround Sound discussion group Subject: Re: [Sursound] Array for sound field recording and extend the sound image The mics are omnis It might be stating the obvious here but how would you get ANY directional information out of four OMNI mics close together? :-) Surely to get a fig-8 response you need two CARDIODS back to back (one of which is polarity reversed obviously). Mike Felton ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
At 11:54 08-01-13, Tim Collins wrote: You can make a velocity microphone by subtracting two closely spaced omnis. I seem to recall that Blumlein did this and also found that the s-n ratio was poor. David ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
Without more details, it hard to speculate about problems, but I'll note that subtracting the outputs of two omnis to get a fig-8 response will result in a frequency response that rises 6dB/octave with a 90 degree phase shift relative to the sum. Unless that is corrected, these signals are not suitable for B-format. I have checked my encoder, and definitely right as you said. I have just compensated for the magnitude and lost the phase modification. After modified, the location of audio is right and the sound image have been extended and much natural. But if the location of the sound is on the front of array, the listener cannot perceive clearly ・ whether the audio is in the front or on the back. I think it needs more processing, e.g. add ・ head tracking. If I have I have good result, I will share it with all. But it need more time since ・ I am not familiar with it：） ・ ・ Thanx very much for help from all of you. 华为技术有限公司 Huawei Technologies Co., Ltd. [Company_logo] Phone: Fax: Mobile: Email: 地址：深圳市龙岗区坂田华为基地 邮编：518129 Huawei Technologies Co., Ltd. Bantian, Longgang District,Shenzhen 518129, P.R.China http://www.huawei.com 本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁 止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中 的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130109/4a9de64c/attachment.html -- next part -- A non-text attachment was scrubbed... Name: image001.jpg Type: image/jpeg Size: 6737 bytes Desc: image001.jpg URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130109/4a9de64c/attachment.jpg ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
Without more details, it hard to speculate about problems, but I'll note that subtracting the outputs of two omnis to get a fig-8 response will result in a frequency response that rises 6dB/octave with a 90 degree phase shift relative to the sum. Unless that is corrected, these signals are not suitable for B-format. On Mon, Jan 7, 2013 at 11:31 AM, Martin Leese martin.le...@stanfordalumni.org wrote: Chenrilin wrote: Hello, all I have designed an array of four microphones to get B-format signal. ... Then I decoded them to get the feeding signal for four loudspeakers, and used HRTFs to get the left and right signal for headphone. 1. Furthermore, the experiment is made that a person was walking around the array and say something in an office. After processed by the method above, I find there is a problem that the speech sounds like a person talking and moving around my head but very near to my ears and head. What is the main reasons for this problem? What happens when you decode a walkaround downloaded from Ambisonia.com? That is to say, a walkaround recorded with somebody else's mic. This would allow you to determine whether the problem is with your decoder, or with the way you calculate your B-Format components. Regards, Martin -- Martin J Leese E-mail: martin.leese stanfordalumni.org Web: http://members.tripod.com/martin_leese/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130107/9be8ea4a/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
On Mon, Jan 07, 2013 at 03:12:26PM -0800, Aaron Heller wrote: Without more details, it hard to speculate about problems, but I'll note that subtracting the outputs of two omnis to get a fig-8 response will result in a frequency response that rises 6dB/octave with a 90 degree phase shift relative to the sum. Unless that is corrected, these signals are not suitable for B-format. Exactly, and it could explain the strange effects in the binaural format. But the OP didn't provide any details about the processing he uses to obtain B-format. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
The mics are omnis It might be stating the obvious here but how would you get ANY directional information out of four OMNI mics close together? :-) Surely to get a fig-8 response you need two CARDIODS back to back (one of which is polarity reversed obviously). Mike Felton On 7 January 2013 23:19, Fons Adriaensen f...@linuxaudio.org wrote: On Mon, Jan 07, 2013 at 03:12:26PM -0800, Aaron Heller wrote: Without more details, it hard to speculate about problems, but I'll note that subtracting the outputs of two omnis to get a fig-8 response will result in a frequency response that rises 6dB/octave with a 90 degree phase shift relative to the sum. Unless that is corrected, these signals are not suitable for B-format. Exactly, and it could explain the strange effects in the binaural format. But the OP didn't provide any details about the processing he uses to obtain B-format. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound -- Mike Felton Freelance Sound Supervisor +44 7595 367 228 +44 20 8876 6122 www.feltonsound.co.uk -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130108/c04ff3f2/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
Hi, Seems likely then that the problem is related to the usual in head problem that many (maybe even most) people people have with simple, non matched HRTF based systems, whether driven from decoded Ambisonic signals or from binaurally recorded (dummy head) material. There's been a lot of work on this (just search the AES library, for instance) and there have been many suggestions for solving this but, in my opinion, the only one which has anything like a chance for solving the problem for the majority of listeners is to add head tracking to the system. This is because if the soundscape stays locked to the reference frame of your head (as happens without head tracking), it is _very_ difficult to convince your perceptions that it is anything but in your head and therefore locking the soundscape to the external fixed reference plane by using headtracking instead makes it much more natural to perceive it as external. This is even more important even than having HRTF's that are the same as, or closely matched to, your own (though such individualised responses do help). Strong visual cues can also help and in some cases will be almost as good at moving the perceived reference frame to the external world as you get with headtracking - though this is _very_ dependent on the particular circumstances. Thanks very much. You are so kind. I will have a try as your suggestion. Best regards, Rilin Chen 华为技术有限公司 Huawei Technologies Co., Ltd. [Company_logo] Phone: Fax: Mobile: Email: 地址：深圳市龙岗区坂田华为基地 邮编：518129 Huawei Technologies Co., Ltd. Bantian, Longgang District,Shenzhen 518129, P.R.China http://www.huawei.com 本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁 止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中 的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130108/8214ea82/attachment.html -- next part -- A non-text attachment was scrubbed... Name: image001.jpg Type: image/jpeg Size: 6737 bytes Desc: image001.jpg URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130108/8214ea82/attachment.jpg ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Array for sound field recording and extend the sound image
Hello, all I have designed an array of four microphones to get B-format signal. The coordinates of mics are mic1 (-d/2,0), mic2 (d/2,0), mic3 (0, d/2), mic4 (0,-d/2),and d is about 18mm.Every opposite pair can be composed into a first order differential array and get a pattern of figure 8. So the X component can be got from mic1 and mic2, the Y component can be get from mic3 and mic4. The W component equals to the mean of signals from four mics. Then I decoded them to get the feeding signal for four loudspeakers, and used HRTFs to get the left and right signal for headphone. 1. Furthermore, the experiment is made that a person was walking around the array and say something in an office. After processed by the method above, I find there is a problem that the speech sounds like a person talking and moving around my head but very near to my ears and head. What is the main reasons for this problem? Is there any suggestion to make it sounds much further from the ears and head. 2. Do I need to add the early reflection and late reverberation to the four loudspeakers? In my understanding, the recording signal of array has included the reflection and late reverberation signal of the office. If add another reflection signal to the feeding signal of loudspeakers, they will contain two kind of reflection signal. Is my understanding right? Apologize for this simple question. Thanks advanced. 华为技术有限公司 Huawei Technologies Co., Ltd. [Company_logo] Phone: Fax: Mobile: Email: 地址：深圳市龙岗区坂田华为基地 邮编：518129 Huawei Technologies Co., Ltd. Bantian, Longgang District,Shenzhen 518129, P.R.China http://www.huawei.com 本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁 止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中 的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130106/0a009956/attachment.html -- next part -- A non-text attachment was scrubbed... Name: image001.jpg Type: image/jpeg Size: 6737 bytes Desc: image001.jpg URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130106/0a009956/attachment.jpg ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
Hello, all [ ... ] The W component equals to the mean of signals from four mics. Then I decoded them to get the feeding signal for four loudspeakers, and used HRTFs to get the left and right signal for headphone. 1. Furthermore, the experiment is made that a person was walking around the array and say something in an office. After processed by the method above, I find there is a problem that the speech sounds like a person talking and moving around my head but very near to my ears [ ... ] Do you get the same problem if you playback through four loudspeakers, or is it only after HRTF manipulation ? (I cannot see how it would cause this, but: Have you controlled to see if W is at the correct level compared with X and Y (depends a lot on the polar pattern of your mic's). Probably would need to analyse some recordings of 'point' sources to check that.) Michael ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
On Sun, Jan 06, 2013 at 09:18:43AM +, Chenrilin wrote: Hello, all I have designed an array of four microphones to get B-format signal. The coordinates of mics are mic1 (-d/2,0), mic2 (d/2,0), mic3 (0, d/2), mic4 (0,-d/2),and d is about 18mm.Every opposite pair can be composed into a first order differential array and get a pattern of figure 8. So the X component can be got from mic1 and mic2, the Y component can be get from mic3 and mic4. The W component equals to the mean of signals from four mics. Then I decoded them to get the feeding signal for four loudspeakers, and used HRTFs to get the left and right signal for headphone. 1. Furthermore, the experiment is made that a person was walking around the array and say something in an office. After processed by the method above, I find there is a problem that the speech sounds like a person talking and moving around my head but very near to my ears and head. What is the main reasons for this problem? Is there any suggestion to make it sounds much further from the ears and head. 2. Do I need to add the early reflection and late reverberation to the four loudspeakers? In my understanding, the recording signal of array has included the reflection and late reverberation signal of the office. If add another reflection signal to the feeding signal of loudspeakers, they will contain two kind of reflection signal. Is my understanding right? Apologize for this simple question. We'll need a bit more information. * Are the mics omnis, or directional ? If directional, what are the directions ? * How exactly to you compute X and Y frm the mic signals ? * Does the decoding work on speakers (without HRTF) ? Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Array for sound field recording and extend the sound image
Do you get the same problem if you playback through four loudspeakers, or is it only after HRTF manipulation ? We'll need a bit more information. * Are the mics omnis, or directional ? If directional, what are the directions ? * How exactly to you compute X and Y frm the mic signals ? * Does the decoding work on speakers (without HRTF) ? The mics are omnis. And it can work on speakers well. So I think X and Y computed is exactly for decoder. 华为技术有限公司 Huawei Technologies Co., Ltd. [Company_logo] Phone: Fax: Mobile: Email: 地址：深圳市龙岗区坂田华为基地 邮编：518129 Huawei Technologies Co., Ltd. Bantian, Longgang District,Shenzhen 518129, P.R.China http://www.huawei.com 本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁 止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中 的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130107/831982b8/attachment.html -- next part -- A non-text attachment was scrubbed... Name: image001.jpg Type: image/jpeg Size: 6737 bytes Desc: image001.jpg URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20130107/831982b8/attachment.jpg ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
