Timeline – Richard Cabot

SC-04-08

Richard Cabot posted an update in the group SC-04-08
3 weeks ago
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<TITLE> [SC-04-08] [Liaisons] Liaison from SMPTE to AES re Modern Theatre Calibration </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] [Liaisons] Liaison from SMPTE to AES re Modern Theatre Calibration</H1> John Woodgate <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20%5BLiaisons%5D%20Liaison%20from%20SMPTE%20to%20AES%20re%0A%09Modern%09Theatre%20Calibration&In-Reply-To=%3C1uHs2Zde0WPUFw2P%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] [Liaisons] Liaison from SMPTE to AES re Modern Theatre Calibration">jmw at jmwa.demon.co.uk </A> Tue Oct 14 12:36:14 MDT 2014 <UL> <LI>Previous message: <A HREF="000210.html">[SC-04-08] [Liaisons] Liaison from SMPTE to AES re Modern Theatre Calibration </A></li> <LI>Next message: <A HREF="000216.html">[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </A></li> <LI> Messages sorted by: <a href="date.html#211">[ date ]</a> <a href="thread.html#211">[ thread ]</a> <a href="subject.html#211">[ subject ]</a> <a href="author.html#211">[ author ]</a> </LI> </UL> <HR>  <PRE>In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">CAEEhACk10HKFGaj19MAy6iP6AAer+9UMKMoWSqYBGZJQCuNXfQ at mail.gmail.com</A>>, dated Tue, 14 Oct 2014, philip newell <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">philiprnewell at gmail.com</A>> writes: > Which working group; SMPTE or AES? This sort of 'leakage' is a 'feature' of email. Sometimes one cannot see how it happened, but in this case, Jean-Luc 'hi-jacked' a liaison message relevant to both SMPTE and AES to post to SC-04-08 only. It is rather easy to do that quite inadvertently. One has to take care. but once it's done, it's done and the only fix is indeed to stop doing it. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Quid faciamus nisi sit? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000210.html">[SC-04-08] [Liaisons] Liaison from SMPTE to AES re Modern Theatre Calibration </A></li> <LI>Next message: <A HREF="000216.html">[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </A></li> <LI> Messages sorted by: <a href="date.html#211">[ date ]</a> <a href="thread.html#211">[ thread ]</a> <a href="subject.html#211">[ subject ]</a> <a href="author.html#211">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] Yamaha NS-10 </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Yamaha NS-10</H1> John Woodgate <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Yamaha%20NS-10&In-Reply-To=%3C7zu%24hzs4gnPUFwnN%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] Yamaha NS-10">jmw at jmwa.demon.co.uk </A> Wed Oct 15 07:35:52 MDT 2014 <UL> <LI>Previous message: <A HREF="000208.html">[SC-04-08] X215 Introduction </A></li> <LI>Next message: <A HREF="000213.html">[SC-04-08] X215 comments due in one week </A></li> <LI> Messages sorted by: <a href="date.html#212">[ date ]</a> <a href="thread.html#212">[ thread ]</a> <a href="subject.html#212">[ subject ]</a> <a href="author.html#212">[ author ]</a> </LI> </UL> <HR>  <PRE>In September, the British journal Engineering and Technology ran a 'mechanical design review' of the NS-10, which has prompted a letter to the journal explaining that the NS-10 was used as a 'typical home loudspeaker' (as was its predecessor Auratone Sound Cube), and that its defects were well-recognized. I suspect they were not recognized by everyone. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Quid faciamus nisi sit? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000208.html">[SC-04-08] X215 Introduction </A></li> <LI>Next message: <A HREF="000213.html">[SC-04-08] X215 comments due in one week </A></li> <LI> Messages sorted by: <a href="date.html#212">[ date ]</a> <a href="thread.html#212">[ thread ]</a> <a href="subject.html#212">[ subject ]</a> <a href="author.html#212">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] X215 comments due in one week </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] X215 comments due in one week</H1> Brian Long <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20X215%20comments%20due%20in%20one%20week&In-Reply-To=%3C8DBDC6D514F3F44B99EA56F331381FE1C32DAAF7%40mailbox12.lucas.alllucas.com%3E" TITLE="[SC-04-08] X215 comments due in one week">blong at skysound.com </A> Fri Oct 24 12:29:45 MDT 2014 <UL> <LI>Previous message: <A HREF="000212.html">[SC-04-08] Yamaha NS-10 </A></li> <LI>Next message: <A HREF="000214.html">[SC-04-08] X215 comments due in one week </A></li> <LI> Messages sorted by: <a href="date.html#213">[ date ]</a> <a href="thread.html#213">[ thread ]</a> <a href="subject.html#213">[ subject ]</a> <a href="author.html#213">[ author ]</a> </LI> </UL> <HR>  <PRE>Dear SC 04-08 Colleagues, This is a reminder that the comment period on the documents provided by SMPTE for X215 will close in one week. Links to those documents are below in the original email. Regards, Brian Long -----Original Message----- From: Brian Long Sent: Monday, October 13, 2014 6:58 PM To: Working group on Measurement and equalization of sound systems in rooms Subject: X215 Introduction Dear SC -04-08 Colleagues, The Society of Motion Picture Engineers has delivered documents for review as part of the AES X215 project on the modern calibration of cinemas. The development of these documents followed a detailed course starting with a bench test comparison of equipment, through an industry survey, to document development. Following is an overview of what was accomplished in each phase: 1. The bench testing group conducted an analysis of various commercially available RTA and transfer function analysis devices in a laboratory setting. This analysis identified any differences in measurements between the types of devices in the electrical domain. Information on various devices settings that could lead to differences in observed readings were noted. Nuisance variables were explored and discussed including differences in microphones, pre amplifiers, and interpretation of device settings. 2. An industry survey was conducted of technicians who had primary responsibilities of maintaining commercial exhibition spaces and/or content creation spaces (dubbing stages). The survey revealed and documented the knowledge spread and a variety of methods used in the field to calibrate cinemas. 3. A draft document was developed to provide guidance and a basis of information for the calibration process. This document also includes recommendations for the use of transfer function devices. This document is a stop gap measure. It is designed to codify current practices and provide guidance to eliminate nuisance variables as found in the research work while maintaining a streamlined work flow. This work is not proposing alteration of the target curve. Planned future work will continue after this document is complete to evolve calibration methods. The document is quite long. It is not necessary to provide comments across the entire document if you do not wish to. Of particular interest we would welcome comments on the sections regarding microphone placement and number of locations, and under the transfer function use procedures. If additional clarifying background information is needed please send any questions my way. I look forward to your comments by Nov. 1. Please see the document for instructions on the preferred method for providing comments. Direct download links: Word: <A HREF="https://secure.aes.org/standards/documents/?ID=91&file=%2Fx215%2D141002%2DDRAFT%2DSMPTE%2DModern%2DCalibration%2Edocx&filesize=1121542">https://secure.aes.org/standards/documents/?ID=91&file=%2Fx215%2D141002%2DDRAFT%2DSMPTE%2DModern%2DCalibration%2Edocx&filesize=1121542</A> PDF: <A HREF="https://secure.aes.org/standards/documents/?ID=91&file=%2Fx215%2Dx216%2DSMPTE%2Dto%2DAES%2Dre%2DModern%2DCalibration%2Dand%2DPink%2DNoise%2D2014%2D09%2D24%2Dfinal%2Epdf&filesize=61177">https://secure.aes.org/standards/documents/?ID=91&file=%2Fx215%2Dx216%2DSMPTE%2Dto%2DAES%2Dre%2DModern%2DCalibration%2Dand%2DPink%2DNoise%2D2014%2D09%2D24%2Dfinal%2Epdf&filesize=61177</A> Regards, Brian Long </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000212.html">[SC-04-08] Yamaha NS-10 </A></li> <LI>Next message: <A HREF="000214.html">[SC-04-08] X215 comments due in one week </A></li> <LI> Messages sorted by: <a href="date.html#213">[ date ]</a> <a href="thread.html#213">[ thread ]</a> <a href="subject.html#213">[ subject ]</a> <a href="author.html#213">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] X215 comments due in one week </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] X215 comments due in one week</H1> David Josephson <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20X215%20comments%20due%20in%20one%20week&In-Reply-To=%3C544AE9D2.5050502%40josephson.com%3E" TITLE="[SC-04-08] X215 comments due in one week">dlj at josephson.com </A> Fri Oct 24 18:07:46 MDT 2014 <UL> <LI>Previous message: <A HREF="000213.html">[SC-04-08] X215 comments due in one week </A></li> <LI>Next message: <A HREF="000215.html">[SC-04-08] X215 comments due in one week </A></li> <LI> Messages sorted by: <a href="date.html#214">[ date ]</a> <a href="thread.html#214">[ thread ]</a> <a href="subject.html#214">[ subject ]</a> <a href="author.html#214">[ author ]</a> </LI> </UL> <HR>  <PRE>Hello SC-04-08 and SMPTE friends, The overall strategy suggested in the SMPTE draft looks OK, but this is not my main area of expertise. There is one major problem that I do know about, and before finishing my comments I would like to hear the rationale for the suggestions made regarding microphones. For a given microphone geometry, the three types noted have identical response corrections (see e.g. the B&K catalog where the same corrections apply to all half-inch mics.) Any omnidirectional microphone having a single diaphragm substantially occupying one end of a cylinder of given size will exhibit the same variation in frequency response for sounds arriving on axis vs. at other angles. The difference between a "free-field" microphone and a "diffuse-field" is that the free-field microphone is built to have flat response on-axis, while the diffuse-field microphone is built to have flat response to a diffuse or random sound field. But, in order for this to be true, the incidence must in fact be random over the measurement interval, not at some arbitrary angle you pick. You must sample the sound field in many directions and average the result! You don't get a spherical diffuse-field measurement with any single microphone, unless it is much smaller than the wavelength of sound being measured. Typically it's done either with a mechanical rotating boom, or a multiplexer with several microphones pointing in different directions, or a very small microphone. A "pressure response" microphone is intended for use only with a closed pressure coupler such as is used for hearing aid calibration. Generally the pressure and random incidence responses are close up to about 10 kHz, so some manufacturers say they are the same. There can be differences in where the pressure equalization vent is located, but this is of no concern in room acoustics. I will prepare a suggested revision text this weekend, but would like to hear what was intended. If there is consensus that experience favors the use of a diffuse-field microphone pointed straight up (as I would expect,) that approach should be specified in the RP. Do not leave it an open choice. Was that the intent? The others will produce a different result. But, there is no difference here between using a free-field microphone pointed up, equalized for flat response at 90 degrees, and a diffuse-field microphone pointed up, with inherently flat response at 90 degrees. Each will have an on-axis response about +4 dB at 10 kHz and +8 at 20 kHz relative to on-axis response, see the Microtech Gefell MK221 for instance at www.josephson.com/mtgd/MK221_MK223_S1+2.pdf These curves apply with small variations to *all* mics with that basic topology. While it is not correct to say that a microphone has a uniform response to sounds arriving from *all* angles, you can say that for all angles substantially normal to the axis of the mic. If the microphone is pointing up, signals reflected from the ceiling will have boosted HF response, and reflections from the floor and seats will have attenuated HF response. This is why this technique works in rooms, so long as you don't have speakers in the ceiling, and it isn't too reverberant. The document should not suggest that one manufacturer's product is more suitable than another's. Physics is the same for everybody. The B&K "Multi-Field" (TM) microphone has directivity no different from any other 1/4" microphone (about -4 dB at 90 degrees at 20 kHz vs on-axis) and might be a good solution, but not uniquely so. There are many other 1/4" mics, and at the sound pressure levels we're talking about in theaters, noise floor (the new B&K's strong suit) should not be an issue. It is inappropriate to use sound level meter (SLM) specifications to recommend microphone types. Many microphone makers use the IEC 61672 or ANSI S1.4 "class" or "type" ratings for their microphones, but this is misleading. The standards do not support this designation. The SLM standards include tolerances, but you have no way of knowing how much of the tolerance budget is taken by the microphone variations and how much by the SLM circuitry. If you want a given tolerance you should specify it, and it should include both the microphone and the amplifier/converter circuit. The IEC 61094 series is a more suitable reference, but probably overkill for the measurements needed here. I'll have some other comments on the number and position of microphones, and how to tell when you have enough. In this regard the draft is already on the right path, also the microphone positioning with respect to seat backs seems OK. In both cases the proof will be to make measurements and look at the variation. Regards David Josephson Josephson Engineering, Inc. Chair, SC-04 on Acoustics Chair, SC-04-04 on Microphone Measurement and Characterization </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000213.html">[SC-04-08] X215 comments due in one week </A></li> <LI>Next message: <A HREF="000215.html">[SC-04-08] X215 comments due in one week </A></li> <LI> Messages sorted by: <a href="date.html#214">[ date ]</a> <a href="thread.html#214">[ thread ]</a> <a href="subject.html#214">[ subject ]</a> <a href="author.html#214">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft</H1> AES Standards <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20x215%20comments%20required%20re%20SMPTE%20Modern%20Theatre%0A%09Calibration%20draft&In-Reply-To=%3CEB52F2C1-D840-4A44-A59B-BFBE18206F11%40aes.org%3E" TITLE="[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft">standards at aes.org </A> Sun Oct 26 06:15:27 MDT 2014 <UL> <LI>Previous message: <A HREF="000211.html">[SC-04-08] [Liaisons] Liaison from SMPTE to AES re Modern Theatre Calibration </A></li> <LI>Next message: <A HREF="000217.html">[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </A></li> <LI> Messages sorted by: <a href="date.html#216">[ date ]</a> <a href="thread.html#216">[ thread ]</a> <a href="subject.html#216">[ subject ]</a> <a href="author.html#216">[ author ]</a> </LI> </UL> <HR>  <PRE>Dear SC-04-08, on 3 October, I posted a copy of a draft SMPTE document to this group, "x215-141002-DRAFT-SMPTE-Modern-Calibration.docx". This drraft was discussed in Los Angeles during the AES137th Convention. SMPTE clearly need tp progress this document promptly and have requested comments by the end of this month. Please talk a moment to download and review this draft documnt. Please send your comments to this email reflector in the first instance. Your comments should identify text in the draft and propose alternative or additional text wherever practicable. If you feel a need to mark up the MS Word document, please upload your marked-up verson taking care to update the filename to include your own name. As soon as possible in the week of 3 Nov, I intend to collate the various responses to SMPTE. Sincerely, Mark Begin forwarded message: > From: AES Standards <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A>> > Date: 3 October 2014 17:45:43 CEST > To: Alan Lambshead <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">alan.lambshead at icloud.com</A>> > Cc: AES Standards <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A>>, Working group on Measurement and equalization of sound systems in rooms <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">sc-04-08 at standards.aes.org</A>>, Brian Vessa <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">Brian_Vessa at spe.sony.com</A>>, <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">liaisons at lists.smpte.org</A>, Kurt Graffy <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">kurt.graffy at arup.com</A>>, Peter Symes <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">psymes at smpte.org</A>>, Bruce Olson <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">BCO at aes.org</A>> > Subject: Re: Liaison from SMPTE to AES re Modern Theatre Calibration > > Dear Alan, > > Thank you for this note and the accompanying draft . I should clearly have checked all your notes before responding to the first! > > Thank you for your note. I have posted it to the SC-04-08 working-group secure document site with the filename, "x215-141002-DRAFT-SMPTE-Modern-Calibration.docx". A direct login is available for SC-04-08 members at:<A HREF="https://secure.aes.org/standards/documents/?ID=91">https://secure.aes.org/standards/documents/?ID=91</A> > > As already mentioned, this SMPTE draft will be discussed under liaison project AES-X215 during the SC-04-08 meeting next Thursday. > > SC-04-08 members please note: this draft is provided confidentially under a liaison agreement between AES and SMPTE. You may not distribute it further. > > regards, > > Mark Yonge > AES Standards Manager > > > On 2014-10-03, at 03:10, Alan Lambshead wrote: > >> Mark >> >> Please find attached a liaison from SMPTE to AES requesting comments on the Modern Theatre Calibration work that SMPTE is undertaking. >> >> <SMPTE-to-AES-re-Modern-Calibration-2014-10-02.pdf> >> >> <SMPTE-Modern-Calibration-RP-for-AES-comment 2014-10-02.docx> >> >> >> Alan Lambshead >> <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">alan.lambshead at icloud.com</A> >> Phone:+1 (416) 848-3119 > > > Mark Yonge > AES Standards Manager > > <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A> > tel: +44 1594 517200 > skype: markyonge </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000211.html">[SC-04-08] [Liaisons] Liaison from SMPTE to AES re Modern Theatre Calibration </A></li> <LI>Next message: <A HREF="000217.html">[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </A></li> <LI> Messages sorted by: <a href="date.html#216">[ date ]</a> <a href="thread.html#216">[ thread ]</a> <a href="subject.html#216">[ subject ]</a> <a href="author.html#216">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] X215 comments due in one week </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] X215 comments due in one week</H1> Brian Long <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20X215%20comments%20due%20in%20one%20week&In-Reply-To=%3C8DBDC6D514F3F44B99EA56F331381FE1C32DAC6F%40mailbox12.lucas.alllucas.com%3E" TITLE="[SC-04-08] X215 comments due in one week">blong at skysound.com </A> Fri Oct 24 19:39:59 MDT 2014 <UL> <LI>Previous message: <A HREF="000214.html">[SC-04-08] X215 comments due in one week </A></li> <LI>Next message: <A HREF="000282.html">[SC-04-08] X215 comments due in one week </A></li> <LI> Messages sorted by: <a href="date.html#215">[ date ]</a> <a href="thread.html#215">[ thread ]</a> <a href="subject.html#215">[ subject ]</a> <a href="author.html#215">[ author ]</a> </LI> </UL> <HR>  <PRE>Hello David, Thank you for comments and questions. See below for answers. "I will prepare a suggested revision text this weekend, but would like to hear what was intended. If there is consensus that experience favors the use of a diffuse-field microphone pointed straight up (as I would expect,) that approach should be specified in the RP. Do not leave it an open choice. Was that the intent?" While your expectation is correct it was noted by the SMPTE drafting committee in discussions and as evidenced from the survey done by the SMPTE committee of technicians in the field that a single specification may not be adhered to. As such additional background information and procedures have been included to assist folks in making choices that translate. Wording can definitely be stronger in some cases. There is also the recognition from the committee as evidenced in the survey that technicians in some cases do not even know what class of microphone they have. Once and if a technician figures that out they may not have the option to obtain or purchase the recommended type if they do not have it. What then? The committee felt it was best to include guiding information to satisfy cases based on equipment shown to be used in the field by the survey. Additionally microphone positions have been another greatly discussed topic. The AES paper presented by Cengarie and Mateos provides the guiding academic information for the approach. That is then combined with the limitations of typical equipment in the field and what that equipment allows for inputs and what time allows for additional positions based on the average technician's time allowed by circumstance to tune a room. The microphone discussions have been particularly detailed. I look forward to the additional expertise and comments. Regards, Brian Long -----Original Message----- From: <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">sc-04-08-bounces at standards.aes.org</A> [mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">sc-04-08-bounces at standards.aes.org</A>] On Behalf Of David Josephson Sent: Friday, October 24, 2014 5:08 PM To: Working group on Measurement and equalization of sound systems in rooms Subject: Re: [SC-04-08] X215 comments due in one week Hello SC-04-08 and SMPTE friends, The overall strategy suggested in the SMPTE draft looks OK, but this is not my main area of expertise. There is one major problem that I do know about, and before finishing my comments I would like to hear the rationale for the suggestions made regarding microphones. For a given microphone geometry, the three types noted have identical response corrections (see e.g. the B&K catalog where the same corrections apply to all half-inch mics.) Any omnidirectional microphone having a single diaphragm substantially occupying one end of a cylinder of given size will exhibit the same variation in frequency response for sounds arriving on axis vs. at other angles. The difference between a "free-field" microphone and a "diffuse-field" is that the free-field microphone is built to have flat response on-axis, while the diffuse-field microphone is built to have flat response to a diffuse or random sound field. But, in order for this to be true, the incidence must in fact be random over the measurement interval, not at some arbitrary angle you pick. You must sample the sound field in many directions and average the result! You don't get a spherical diffuse-field measurement with any single microphone, unless it is much smaller than the wavelength of sound being measured. Typically it's done either with a mechanical rotating boom, or a multiplexer with several microphones pointing in different directions, or a very small microphone. A "pressure response" microphone is intended for use only with a closed pressure coupler such as is used for hearing aid calibration. Generally the pressure and random incidence responses are close up to about 10 kHz, so some manufacturers say they are the same. There can be differences in where the pressure equalization vent is located, but this is of no concern in room acoustics. I will prepare a suggested revision text this weekend, but would like to hear what was intended. If there is consensus that experience favors the use of a diffuse-field microphone pointed straight up (as I would expect,) that approach should be specified in the RP. Do not leave it an open choice. Was that the intent? The others will produce a different result. But, there is no difference here between using a free-field microphone pointed up, equalized for flat response at 90 degrees, and a diffuse-field microphone pointed up, with inherently flat response at 90 degrees. Each will have an on-axis response about +4 dB at 10 kHz and +8 at 20 kHz relative to on-axis response, see the Microtech Gefell MK221 for instance at www.josephson.com/mtgd/MK221_MK223_S1+2.pdf These curves apply with small variations to *all* mics with that basic topology. While it is not correct to say that a microphone has a uniform response to sounds arriving from *all* angles, you can say that for all angles substantially normal to the axis of the mic. If the microphone is pointing up, signals reflected from the ceiling will have boosted HF response, and reflections from the floor and seats will have attenuated HF response. This is why this technique works in rooms, so long as you don't have speakers in the ceiling, and it isn't too reverberant. The document should not suggest that one manufacturer's product is more suitable than another's. Physics is the same for everybody. The B&K "Multi-Field" (TM) microphone has directivity no different from any other 1/4" microphone (about -4 dB at 90 degrees at 20 kHz vs on-axis) and might be a good solution, but not uniquely so. There are many other 1/4" mics, and at the sound pressure levels we're talking about in theaters, noise floor (the new B&K's strong suit) should not be an issue. It is inappropriate to use sound level meter (SLM) specifications to recommend microphone types. Many microphone makers use the IEC 61672 or ANSI S1.4 "class" or "type" ratings for their microphones, but this is misleading. The standards do not support this designation. The SLM standards include tolerances, but you have no way of knowing how much of the tolerance budget is taken by the microphone variations and how much by the SLM circuitry. If you want a given tolerance you should specify it, and it should include both the microphone and the amplifier/converter circuit. The IEC 61094 series is a more suitable reference, but probably overkill for the measurements needed here. I'll have some other comments on the number and position of microphones, and how to tell when you have enough. In this regard the draft is already on the right path, also the microphone positioning with respect to seat backs seems OK. In both cases the proof will be to make measurements and look at the variation. Regards David Josephson Josephson Engineering, Inc. Chair, SC-04 on Acoustics Chair, SC-04-04 on Microphone Measurement and Characterization _______________________________________________ SC-04-08 mailing list <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">SC-04-08 at standards.aes.org</A> <<A HREF="http://standards.aes.org/sc.cfm?ID=91">http://standards.aes.org/sc.cfm?ID=91</A>> </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000214.html">[SC-04-08] X215 comments due in one week </A></li> <LI>Next message: <A HREF="000282.html">[SC-04-08] X215 comments due in one week </A></li> <LI> Messages sorted by: <a href="date.html#215">[ date ]</a> <a href="thread.html#215">[ thread ]</a> <a href="subject.html#215">[ subject ]</a> <a href="author.html#215">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft</H1> David Josephson <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20x215%20comments%20required%20re%20SMPTE%20Modern%20Theatre%0A%20Calibration%20draft&In-Reply-To=%3C544D1C73.5020001%40josephson.com%3E" TITLE="[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft">dlj at josephson.com </A> Sun Oct 26 10:08:19 MDT 2014 <UL> <LI>Previous message: <A HREF="000216.html">[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </A></li> <LI>Next message: <A HREF="000218.html">[SC-04-08] x215 and x216 comments required re SMPTE Modern Theatre Calibration draft and Digital Pink Noise signal </A></li> <LI> Messages sorted by: <a href="date.html#217">[ date ]</a> <a href="thread.html#217">[ thread ]</a> <a href="subject.html#217">[ subject ]</a> <a href="author.html#217">[ author ]</a> </LI> </UL> <HR>  <PRE>I am preparing comments and revised language specifically with regard to microphone selection and placement, and understanding the room acoustics issues that the microphone measurements are intended to diagnose. Brian Long's earlier response reminds me that this document is intended as a recommended practice for field technicians, not necessarily a standard of laboratory correctness. Toward that end the recommended language should probably be a bit shorter and more tutorial than a standard might usually be. Mark, it's good to hear that Mark will be collating a response to SMPTE, as the document itself asks only that comments be submitted as annotated versions of the Word document. David Josephson On 10/26/14 5:15 AM, AES Standards wrote: > Dear SC-04-08, > > on 3 October, I posted a copy of a draft SMPTE document to this > group, "x215-141002-DRAFT-SMPTE-Modern-Calibration.docx". > > This drraft was discussed in Los Angeles during the AES137th > Convention. SMPTE clearly need tp progress this document promptly and > have requested comments by the end of this month. > > Please talk a moment to download and review this draft documnt. > > Please send your comments to this email reflector in the first > instance. Your comments should identify text in the draft and propose > alternative or additional text wherever practicable. > > If you feel a need to mark up the MS Word document, please upload > your marked-up verson taking care to update the filename to include > your own name. > > As soon as possible in the week of 3 Nov, I intend to collate the > various responses to SMPTE. > > Sincerely, > > Mark > </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000216.html">[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </A></li> <LI>Next message: <A HREF="000218.html">[SC-04-08] x215 and x216 comments required re SMPTE Modern Theatre Calibration draft and Digital Pink Noise signal </A></li> <LI> Messages sorted by: <a href="date.html#217">[ date ]</a> <a href="thread.html#217">[ thread ]</a> <a href="subject.html#217">[ subject ]</a> <a href="author.html#217">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] x215 and x216 comments required re SMPTE Modern Theatre Calibration draft and Digital Pink Noise signal </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] x215 and x216 comments required re SMPTE Modern Theatre Calibration draft and Digital Pink Noise signal</H1> Vessa, Brian <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20x215%20and%20x216%20comments%20required%20re%20SMPTE%20Modern%0A%20Theatre%20Calibration%20draft%20and%20Digital%20Pink%20Noise%20signal&In-Reply-To=%3CEA1975E3-2F46-4789-A139-982802EC1C3D%40spe.sony.com%3E" TITLE="[SC-04-08] x215 and x216 comments required re SMPTE Modern Theatre Calibration draft and Digital Pink Noise signal">Brian_Vessa at spe.sony.com </A> Sun Oct 26 15:13:05 MDT 2014 <UL> <LI>Previous message: <A HREF="000217.html">[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </A></li> <LI>Next message: <A HREF="000189.html">[SC-04-08] Liaison from SMPTE to AES re Pink Noise </A></li> <LI> Messages sorted by: <a href="date.html#218">[ date ]</a> <a href="thread.html#218">[ thread ]</a> <a href="subject.html#218">[ subject ]</a> <a href="author.html#218">[ author ]</a> </LI> </UL> <HR>  <PRE>Thank you Mark! A reminder that comments are also due on the x216 Pink Noise standard... Thank you, Brian On Oct 26, 2014, at 5:15 AM, "AES Standards" <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A>>> wrote: Dear SC-04-08, on 3 October, I posted a copy of a draft SMPTE document to this group, "x215-141002-DRAFT-SMPTE-Modern-Calibration.docx". This drraft was discussed in Los Angeles during the AES137th Convention. SMPTE clearly need tp progress this document promptly and have requested comments by the end of this month. Please talk a moment to download and review this draft documnt. Please send your comments to this email reflector in the first instance. Your comments should identify text in the draft and propose alternative or additional text wherever practicable. If you feel a need to mark up the MS Word document, please upload your marked-up verson taking care to update the filename to include your own name. As soon as possible in the week of 3 Nov, I intend to collate the various responses to SMPTE. Sincerely, Mark Begin forwarded message: From: AES Standards <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A>>> Date: 3 October 2014 17:45:43 CEST To: Alan Lambshead <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">alan.lambshead at icloud.com</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">alan.lambshead at icloud.com</A>>> Cc: AES Standards <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A>>>, Working group on Measurement and equalization of sound systems in rooms <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">sc-04-08 at standards.aes.org</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">sc-04-08 at standards.aes.org</A>>>, Brian Vessa <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">Brian_Vessa at spe.sony.com</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">Brian_Vessa at spe.sony.com</A>>>, <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">liaisons at lists.smpte.org</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">liaisons at lists.smpte.org</A>>, Kurt Graffy <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">kurt.graffy at arup.com</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">kurt.graffy at arup.com</A>>>, Peter Symes <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">psymes at smpte.org</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">psymes at smpte.org</A>>>, Bruce Olson <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">BCO at aes.org</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">BCO at aes.org</A>>> Subject: Re: Liaison from SMPTE to AES re Modern Theatre Calibration Dear Alan, Thank you for this note and the accompanying draft . I should clearly have checked all your notes before responding to the first! Thank you for your note. I have posted it to the SC-04-08 working-group secure document site with the filename, "x215-141002-DRAFT-SMPTE-Modern-Calibration.docx". A direct login is available for SC-04-08 members at:<A HREF="https://secure.aes.org/standards/documents/?ID=91<http://secure.aes.org/standards/documents/?ID=91">https://secure.aes.org/standards/documents/?ID=91<http://secure.aes.org/standards/documents/?ID=91</A>> As already mentioned, this SMPTE draft will be discussed under liaison project AES-X215 during the SC-04-08 meeting next Thursday. SC-04-08 members please note: this draft is provided confidentially under a liaison agreement between AES and SMPTE. You may not distribute it further. regards, Mark Yonge AES Standards Manager On 2014-10-03, at 03:10, Alan Lambshead wrote: Mark Please find attached a liaison from SMPTE to AES requesting comments on the Modern Theatre Calibration work that SMPTE is undertaking. <SMPTE-to-AES-re-Modern-Calibration-2014-10-02.pdf> <SMPTE-Modern-Calibration-RP-for-AES-comment 2014-10-02.docx> Alan Lambshead <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">alan.lambshead at icloud.com</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">alan.lambshead at icloud.com</A>> Phone:+1 (416) 848-3119 Mark Yonge AES Standards Manager <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A><mailto:<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">standards at aes.org</A>> tel: +44 1594 517200 skype: markyonge </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000217.html">[SC-04-08] x215 comments required re SMPTE Modern Theatre Calibration draft </A></li> <LI>Next message: <A HREF="000189.html">[SC-04-08] Liaison from SMPTE to AES re Pink Noise </A></li> <LI> Messages sorted by: <a href="date.html#218">[ date ]</a> <a href="thread.html#218">[ thread ]</a> <a href="subject.html#218">[ subject ]</a> <a href="author.html#218">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge</H1> Mark Yonge <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Comments%20on%20%22SMPTE-Modern-Calibration%22%3B%20mark%20yonge&In-Reply-To=%3C9EA8F4A9-9DA0-49AC-841B-93A632D11AA7%40aes.org%3E" TITLE="[SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge">mark.yonge at aes.org </A> Mon Oct 27 01:31:07 MDT 2014 <UL> <LI>Previous message: <A HREF="000283.html">[SC-04-08] X215 comments due in one week </A></li> <LI>Next message: <A HREF="000220.html">[SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge </A></li> <LI> Messages sorted by: <a href="date.html#219">[ date ]</a> <a href="thread.html#219">[ thread ]</a> <a href="subject.html#219">[ subject ]</a> <a href="author.html#219">[ author ]</a> </LI> </UL> <HR>  <PRE>INTRODUCTION These comments relate to SMPTE's draft RP document on Modern-Calibration: original filename: "SMPTE-Modern-Calibration-RP-for-AES-comment 2014-10-02.docx" Posted 2014-10-03 to SC-04-08 as "x215-141002-DRAFT-SMPTE-Modern-Calibration.docx" COMMENTS GENERAL RP This "recommended practice" appears to leave much is left to the discretion and experience - "knowledgeable interpretation" - of the technician. Becaus individual cinemas can vary greatly, this is understandable and, I believe necessary. However, this argues against using unskilled technicians in this role, which may have been one of the intended goals. INSTALLATION VS CHECKS Prefer to keep installation issues separate from subsequent checks. It should be possible to confirm the satisfactory alignment of the system without changing any calibration. A simplified procedure for go/no-go performance checks could be included as an annex, with references to the main installation text where necessary. EFFICIENCY How much time should this process take? Would it be better to structure the document for smoother flow on the night? Keep movements between the projection booth, auditorium, and the behind-screen area to a minimum. USE OF ST 202 WITH FFT-BASED ANALYSER The X-curve in ST 202 depends entirely on measuring the acoustic reproduction of continuous pink noise in a reverberant auditorium using a traditonal 1/3-octave real-time audio analyser (TRA). The deviation of the X-curve from a flat trace results from the reverberation contribution which has a higher spl than the direct sound and is dominant at lower frequencies. ST 202 does not specify or require any filter in the signal path; its intent is to allow an imperfect measurement tool (RTA) to predict the amplitude and spectrum of the reverberation component to deduce spectrally-flat direct sound arriving at a typical seat in the auditorium. Unless the FFT analyser in this RP emulates the behaviour of an RTA precisely, the X-curve in ST 202 becomes irrelevant, and a new characteristic needs to be found. (see also below) CLAUSE-SPECIFIC COMMENTS NORMATIVE REFS IEC 61260 Ed.1:1995 has been superseded by IEC 61260-1 Ed.1:2014 " Electroacoustics - Octave-band and fractional-octave-band filters - Part 1: Specifications". I believe that the specifications in the international standard are equivalent to those in ANSI/ASA S1.11. Is it useful to cite both as normative references? TERMINOLOGY Decibel The unit "decibel" is spelled without a mid-cap. The bel, used alone, does not have a capital letter, according to SI. Sampling rate vs sampling frequency Just FYI, it is AES practice to refer to "sampling frequency" (in units of Hertz: Hz) where the sample-timing must be regular - such as in conversion, quantization and re-quantization - and "sampling rate" (in units of kilosamples per second: ksps) where the timing is more loosely-defined, such as in packetized streams, for example. 8.1 LOUDSPEAKERS The draft states, " Verify that all surround loudspeakers with a built-in switchable X-Curve filter are set to the same switch position. It is recommended that such switches be set to flat or off." This implies that some loudspeakers in cinemas have "X-curve" filters fitted. This is fundamentally to misunderstand the X-curve (see above). I can see no purpose for any generalized filter in the signal path of a loudspeaker. I understand that an RP must use the language of recommendation, but propose to replace "recommended" with "strongly recommended" at least. Same comment at A.18.5.2.2 16 DISTORTION SWEEP The proposed single-tone sweep from 20 Hz to 16 kHz seems unnecessarily wide for this purpose. Distortion harmonics of signals above about 8 kHz will be outside the audible spectrum, and the very high level proposed for this sweep (-3 dB FS) will risk damaging components at these high frequencies. Suggest restricting the single-tone high-level sweep to 20 Hz to 8 kHz, max. 18.5.1 SCREEN CHANNEL ELECTROACOUSTIC MEASUREMENTS The type of analysis to be used for these frequency response measurements is not well defined in this clause, and it's very important that it is. 18.5.1 describes using the analyser in transfer-function mode. But 18.5.1.1 asks for adjustments to fit the ST 202 X-curve. Unless I have misunderstood the meaning of "transfer-function mode", and the analyser actually does emulate precisely a traditional RTA measurement, this just doesn't work! To summarize, both cases assuming a continuous pink-noise stimulus: • A single-channel measurement that has been arranged to emulate precisely a traditional RTA measurement, and which measures the whole signal from the microphone including the reverberation component, should be used with the ST 202 X-curve. • A dual channel measurement that uses the source signal to discount the reverberation component in the received microphone signal should NOT be adjusted to the X-curve: it should probably be calibrated to a flat response. Either measurement technique should give an equivalent electroacoustic response in the auditorium - flat direct sound. Same comment at A.18.1 Clarity here is vital, I think. Mark Yonge vice chair, SC-04-08 <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">mark.yonge at aes.org</A> </PRE>  <HR> <UL>  <LI>Previous message: <A HREF="000283.html">[SC-04-08] X215 comments due in one week </A></li> <LI>Next message: <A HREF="000220.html">[SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge </A></li> <LI> Messages sorted by: <a href="date.html#219">[ date ]</a> <a href="thread.html#219">[ thread ]</a> <a href="subject.html#219">[ subject ]</a> <a href="author.html#219">[ author ]</a> </LI> </UL> <hr> <a href="https://secure.aes.org/mailman/listinfo/sc-04-08">More information about the SC-04-08 mailing list</a> 

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<TITLE> [SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge</H1> Brian Long <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Comments%20on%20%22SMPTE-Modern-Calibration%22%3B%20mark%20yonge&In-Reply-To=%3CD073A886.16015%25blong%40skysound.com%3E" TITLE="[SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge">blong at skysound.com </A> Mon Oct 27 08:53:04 MDT 2014 <UL> <LI>Previous message: <A HREF="000219.html">[SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge </A></li> <LI>Next message: <A HREF="000221.html">[SC-04-08] Comments on "SMPTE-Modern-Calibration"; mark yonge </A></li> <LI> Messages sorted by: <a href="date.html#220">[ date ]</a> <a href="thread.html#220">[ thread ]</a> <a href="subject.html#220">[ subject ]</a> <a href="author.html#220">[ author ]</a> </LI> </UL> <HR>  <PRE>Hello All, Some of the statements in the comments below regarding the X-Curve have been proven incorrect with recent research and paper presentations. The conclusion has been that the X-Curve as observed in modern cinemas is mostly caused by the screen and loudspeaker interaction. Minor variation to that result of the loudspeaker and screen interaction is caused by reverb characteristics of the room and air absorption. This can be seen in the paper: <A HREF="http://conferences.smpte.org/content/2012/10/1.50.refs">http://conferences.smpte.org/content/2012/10/1.50.refs</A> Presented in the SMPTE Journal as: <A HREF="http://journal.smpte.org/content/121/8/46.abstract">http://journal.smpte.org/content/121/8/46.abstract</A> Additional recent work by Newell et. Al confirms and supports the paper above. The SMPTE also conducted specific tests comparing the results of RTA v. FFT measurements and recommendations in this RP on the bench in the electrical domain and in a modern cinema environment. It was found that deviation in a typical cinema adhering to RT as per THX specifications was minimal. It was noted the circumstances that caused the RTA to differ from the FFT based measurements. Regards, Brian Long On 10/27/14, 12:31 AM, "Mark Yonge" <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">mark.yonge at aes.org</A>> wrote: >INTRODUCTION > >These comments relate to SMPTE's draft RP document on Modern-Calibration: > >original filename: "SMPTE-Modern-Calibration-RP-for-AES-comment >2014-10-02.docx" > >Posted 2014-10-03 to SC-04-08 as >"x215-141002-DRAFT-SMPTE-Modern-Calibration.docx" > >COMMENTS > >GENERAL > >RP > >This "recommended practice" appears to leave much is left to the >discretion and experience - "knowledgeable interpretation" - of the >technician. Becaus individual cinemas can vary greatly, this is >understandable and, I believe necessary. However, this argues against >using unskilled technicians in this role, which may have been one of the >intended goals. > > >INSTALLATION VS CHECKS > >Prefer to keep installation issues separate from subsequent checks. > >It should be possible to confirm the satisfactory alignment of the system >without changing any calibration. A simplified procedure for go/no-go >performance checks could be included as an annex, with references to the >main installation text where necessary. > > >EFFICIENCY > >How much time should this process take? > >Would it be better to structure the document for smoother flow on the >night? Keep movements between the projection booth, auditorium, and the >behind-screen area to a minimum. > >USE OF ST 202 WITH FFT-BASED ANALYSER > >The X-curve in ST 202 depends entirely on measuring the acoustic >reproduction of continuous pink noise in a reverberant auditorium using a >traditonal 1/3-octave real-time audio analyser (TRA). The deviation of >the X-curve from a flat trace results from the reverberation contribution >which has a higher spl than the direct sound and is dominant at lower >frequencies. ST 202 does not specify or require any filter in the signal >path; its intent is to allow an imperfect measurement tool (RTA) to >predict the amplitude and spectrum of the reverberation component to >deduce spectrally-flat direct sound arriving at a typical seat in the >auditorium. > >Unless the FFT analyser in this RP emulates the behaviour of an RTA >precisely, the X-curve in ST 202 becomes irrelevant, and a new >characteristic needs to be found. (see also below) > >CLAUSE-SPECIFIC COMMENTS > >NORMATIVE REFS > >IEC 61260 Ed.1:1995 has been superseded by IEC 61260-1 Ed.1:2014 " >Electroacoustics - Octave-band and fractional-octave-band filters - Part >1: Specifications". I believe that the specifications in the >international standard are equivalent to those in ANSI/ASA S1.11. Is it >useful to cite both as normative references? > >TERMINOLOGY > >Decibel > >The unit "decibel" is spelled without a mid-cap. The bel, used alone, >does not have a capital letter, according to SI. > >Sampling rate vs sampling frequency > >Just FYI, it is AES practice to refer to "sampling frequency" (in units >of Hertz: Hz) where the sample-timing must be regular - such as in >conversion, quantization and re-quantization - and "sampling rate" (in >units of kilosamples per second: ksps) where the timing is more >loosely-defined, such as in packetized streams, for example. > >8.1 LOUDSPEAKERS > >The draft states, " Verify that all surround loudspeakers with a built-in >switchable X-Curve filter are set to the same switch position. It is >recommended that such switches be set to flat or off." > >This implies that some loudspeakers in cinemas have "X-curve" filters >fitted. This is fundamentally to misunderstand the X-curve (see above). I >can see no purpose for any generalized filter in the signal path of a >loudspeaker. I understand that an RP must use the language of >recommendation, but propose to replace "recommended" with "strongly >recommended" at least. > >Same comment at A.18.5.2.2 > >16 DISTORTION SWEEP > >The proposed single-tone sweep from 20 Hz to 16 kHz seems unnecessarily >wide for this purpose. Distortion harmonics of signals above about 8 kHz >will be outside the audible spectrum, and the very high level proposed >for this sweep (-3 dB FS) will risk damaging components at these high >frequencies. > >Suggest restricting the single-tone high-level sweep to 20 Hz to 8 kHz, >max. > >18.5.1 SCREEN CHANNEL ELECTROACOUSTIC MEASUREMENTS > >The type of analysis to be used for these frequency response measurements >is not well defined in this clause, and it's very important that it is. > >18.5.1 describes using the analyser in transfer-function mode. But >18.5.1.1 asks for adjustments to fit the ST 202 X-curve. Unless I have >misunderstood the meaning of "transfer-function mode", and the analyser >actually does emulate precisely a traditional RTA measurement, this just >doesn't work! > >To summarize, both cases assuming a continuous pink-noise stimulus: > >€ A single-channel measurement that has been arranged to emulate >precisely a traditional RTA measurement, and which measures the whole >signal from the microphone including the reverberation component, should >be used with the ST 202 X-curve. > >€ A dual channel measurement that uses the source signal to discount the >reverberation component in the received microphone signal should NOT be >adjusted to the X-curve: it should probably be calibrated to a flat >response. > >Either measurement technique should give an equivalent electroacoustic >response in ...

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