Timeline – Richard Cabot

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 Brian Long 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3C8DBDC6D514F3F44B99EA56F331381FE1AD2E67EC%40mailbox10.lucas.alllucas.com%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">blong at skysound.com
 </A> 
 Tue Jul 16 18:58:22 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000059.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000062.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#60">[ date ]</a>
 <a href="thread.html#60">[ thread ]</a>
 <a href="subject.html#60">[ subject ]</a>
 <a href="author.html#60">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>The use of 500-2K noise has been a practice (though not standardized) of many for years.

In certain situations it can be preferable.

Home theater noise is generally mid range for different reasons, most notably the wide range of "acoustic variance" in the rooms along with the stated performance variance of speakers in those rooms.

-----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 murphy
Sent: Tuesday, July 16, 2013 5:39 PM
To: 'Working group on Measurement and equalization of sound systems in rooms'
Subject: Re: [SC-04-08] AES-X215 B-Chain level measurements

Hi All,
May I put my 2 cents in.
I believe that we have been talking about full bandwidth pink noise, which I think would have more 'randomness' than if band limited. I notice that in home cinemas the channel alignment signal is a 'mid range' pink noise, to try to minimise differences caused by irregular loudspeaker response. I realise that our cinema systems will have perfectly uniform and consistent frequency responses (I wish!) so band limiting is not necessary for that reason. However one could make a case for band limiting the pink noise to correlate more with the sensitivity (frequency response) of the human ear.
In my experience doing listening tests on loudspeakers, to accurately A-B compare slight differences, you have to set the apparent loudness of each loudspeaker to be as close as possible the same on the same type of programme, eg male singing voice, soprano, flute, bass guitar, or whatever. And then if you listen and compare a different programme type you have to reset the levels to be as close as possible on that programme. So I deduce that perceived sound level is dependent on the band of frequencies one is perceiving.
Should we consider a band limited pink noise source for level setting? Eg 500Hz to 2kHz, or even an existing signal, the shaped pink noise used for loudspeaker testing (EIA-426, IEC 60268-1)?

John Woodgate made a good point about measurement accuracy and consistency, saying that the pink noise must be averaged for a time long enough to get a particular accuracy, so that should be part of the package /specifications.

-----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 Brian Long
Sent: Wednesday, 17 July 2013 9:43 AM
To: Working group on Measurement and equalization of sound systems in rooms
Subject: Re: [SC-04-08] AES-X215 B-Chain level measurements

So all are aware the intended output is:

Specification of a noise.
Digital files.
A D-Cinema package.

CD is a pretty useless format given DCinema  is 24bit 48kHz at the current time with the possibility to move to 96kHz.

Once the specified noise is created and agreed upon the next step is to explore new signals.

-----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 John Woodgate
Sent: Tuesday, July 16, 2013 12:35 PM
To: Working group on Measurement and equalization of sound systems in rooms
Subject: Re: [SC-04-08] AES-X215 B-Chain level measurements

In message
<<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">8DBDC6D514F3F44B99EA56F331381FE1AD2E6142 at mailbox10.lucas.alllucas.com</A>>,
dated Tue, 16 Jul 2013, Brian Long <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">blong at skysound.com</A>> writes:

> In fact if one looks at new bits on the market many manufacturers are 
>already moving beyond pink noise.

That isn't necessarily good news. There is a danger that results with new methods will be compared with results from several different 'flavours' of pink noise, varying in not only *precise* spectrum and crest factor but amplitude-probability distribution.

A reference pink noise on CD would be a help, but it can still produce mangled noise from some 'too clever by half' replay units.
--
OOO - Own Opinions Only. See www.jmwa.demon.co.uk Why is the stapler always empty just when you want it?

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK _______________________________________________
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>>
_______________________________________________
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>>
_______________________________________________
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="000059.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000062.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#60">[ date ]</a>
 <a href="thread.html#60">[ thread ]</a>
 <a href="subject.html#60">[ subject ]</a>
 <a href="author.html#60">[ 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>

Expand

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 John Woodgate 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3CKYB%248QAXqi5RFwW8%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">jmw at jmwa.demon.co.uk
 </A> 
 Tue Jul 16 23:24:39 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000066.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000093.html">[SC-04-08] Workgroup confidentiality
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#61">[ date ]</a>
 <a href="thread.html#61">[ thread ]</a>
 <a href="subject.html#61">[ subject ]</a>
 <a href="author.html#61">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>In message 
<<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">8DBDC6D514F3F44B99EA56F331381FE1AD2E6690 at mailbox10.lucas.alllucas.com</A>>, 
dated Wed, 17 Jul 2013, Brian Long <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">blong at skysound.com</A>> writes:

>So all are aware the intended output is:
>
>Specification of a noise.
>Digital files.
>A D-Cinema package.

Well, it's a good idea to make that clear at an early stage!
>
>CD is a pretty useless format given DCinema is 24bit 48kHz at the 
>current time with the possibility to move to 96kHz.

OK, use whatever medium is compatible.
>
>Once the specified noise is created and agreed upon the next step is to 
>explore new signals.

... preferably including OLD signals; new is not necessarily better, and 
takes longer to evaluate.
-- 
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
Why is the stapler always empty just when you want it?

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
</PRE>

<HR>
 <UL>
 
	<LI>Previous message: <A HREF="000066.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000093.html">[SC-04-08] Workgroup confidentiality
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#61">[ date ]</a>
 <a href="thread.html#61">[ thread ]</a>
 <a href="subject.html#61">[ subject ]</a>
 <a href="author.html#61">[ 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>

Expand

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 John Woodgate 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3Cb4V709AFwi5RFwWX%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">jmw at jmwa.demon.co.uk
 </A> 
 Tue Jul 16 23:30:45 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000060.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000063.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#62">[ date ]</a>
 <a href="thread.html#62">[ thread ]</a>
 <a href="subject.html#62">[ subject ]</a>
 <a href="author.html#62">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>In message 
<<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">8DBDC6D514F3F44B99EA56F331381FE1AD2E67EC at mailbox10.lucas.alllucas.com</A>>, 
dated Wed, 17 Jul 2013, Brian Long <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">blong at skysound.com</A>> writes:

>The use of 500-2K noise has been a practice (though not standardized) 
>of many for years.
>
>In certain situations it can be preferable.

In others, it hides serious problems. Of course, ALL real noise signals 
are band-limited; none cover from DC since the Big Bang to the 
relativistic limit (where the photon has enough energy to become a black 
hole).
-- 
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
Why is the stapler always empty just when you want it?

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
</PRE>

<HR>
 <UL>
 
	<LI>Previous message: <A HREF="000060.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000063.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#62">[ date ]</a>
 <a href="thread.html#62">[ thread ]</a>
 <a href="subject.html#62">[ subject ]</a>
 <a href="author.html#62">[ 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>

Expand

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 Charlie Hughes 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3C5B9CF13FCBF0BD408B0F0A1F63FA94752A0EADC9%40ExDAG40-N1.hostallapps.net%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">charlie at excelsior-audio.com
 </A> 
 Wed Jul 17 11:12:00 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000062.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000064.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#63">[ date ]</a>
 <a href="thread.html#63">[ thread ]</a>
 <a href="subject.html#63">[ subject ]</a>
 <a href="author.html#63">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>If the signal for measurements must be noise, I think there are definite benefits to using shaped, band limited pink noise. Specifying the noise to have the same spectral content as "average" program material should minimize the over excitation of the HF section of loudspeaker systems. Certainly ANSI/CEA-426-B as well as IEC 60268-1 have their "flavors" of noise. CEA should be issuing a new standard shortly with an new flavor of noise, similar to IEC 60268 with increased LF level.

The crest factor and probability density function of the noise should also be specified.  Work in SC-04-03 while pursuing AES2-2012 came to the conclusion that a CF of 12 dB should work well for the test noise.  That reasoning was that with a lower CF, say 6 dB, when the noise was filtered (via required HP filters or the internal crossover filters of loudspeaker systems) the CF of the filter noise tended towards 12 dB.

Charlie Hughes
Excelsior Audio Design & Services, LLC
Gastonia, NC
+1 704.675.5435 (tel)     +1 704.678.6570 (mobile)
+1 704.675.5436 (fax)
www.excelsior-audio.com
 
Copyright 2013 - Excelsior Audio Design & Services, LLC

</PRE>

<HR>
 <UL>
 
	<LI>Previous message: <A HREF="000062.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000064.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#63">[ date ]</a>
 <a href="thread.html#63">[ thread ]</a>
 <a href="subject.html#63">[ subject ]</a>
 <a href="author.html#63">[ 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>

Expand

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 John Woodgate 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3CZF4rrGKyct5RFwkV%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">jmw at jmwa.demon.co.uk
 </A> 
 Wed Jul 17 11:41:06 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000063.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000065.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#64">[ date ]</a>
 <a href="thread.html#64">[ thread ]</a>
 <a href="subject.html#64">[ subject ]</a>
 <a href="author.html#64">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>In message 
<<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">5B9CF13FCBF0BD408B0F0A1F63FA94752A0EADC9 at ExDAG40-N1.hostallapps.net</A>>, 
dated Wed, 17 Jul 2013, Charlie Hughes <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">charlie at excelsior-audio.com</A>> 
writes:

>If the signal for measurements must be noise, I think there are 
>definite benefits to using shaped, band limited pink noise. Specifying 
>the noise to have the same spectral content as "average" program 
>material should minimize the over excitation of the HF section of 
>loudspeaker systems. Certainly ANSI/CEA-426-B as well as IEC 60268-1 
>have their "flavors" of noise. CEA should be issuing a new standard 
>shortly with an new flavor of noise, similar to IEC 60268 with 
>increased LF level.

I hope CEA will propose any new signal to IEC TC100 for inclusion in IEC 
60268-1. Conflicting standards help no-one, and lethargy is not an 
excuse.

The current IEC 60268-1 signal is not a noise signal but a blend of many 
speech and music signals. It is a 'long-term average', with the 
averaging time not defined. Any new signal should have a specified 
averaging time. Short-term average (less than 1 s) spectra of programme 
signals are significantly different from the long-term spectrum in the 
standard.
>
>The crest factor and probability density function of the noise should 
>also be specified. Work in SC-04-03 while pursuing AES2-2012 came to 
>the conclusion that a CF of 12 dB should work well for the test noise. 
>That reasoning was that with a lower CF, say 6 dB, when the noise was 
>filtered (via required HP filters or the internal crossover filters of 
>loudspeaker systems) the CF of the filter noise tended towards 12 dB.

I agree that 12 dB is reasonable. ANY filtering alters the crest factor, 
but when you get to crest factor 5, the big peaks occur so seldom that 
they normally have negligible effect. If you do hit one in a test and 
you can see that it corrupted the results, just run another test.
-- 
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
Why is the stapler always empty just when you want it?

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
</PRE>

<HR>
 <UL>
 
	<LI>Previous message: <A HREF="000063.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000065.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#64">[ date ]</a>
 <a href="thread.html#64">[ thread ]</a>
 <a href="subject.html#64">[ subject ]</a>
 <a href="author.html#64">[ 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>

Expand

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 Pete Soper 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3C2BE563BCBE473946A8E72AE261D4F64BE78CF591%40XCHG2.ms.msli.com%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">psoper at meyersound.com
 </A> 
 Wed Jul 17 14:07:03 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000064.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000067.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#65">[ date ]</a>
 <a href="thread.html#65">[ thread ]</a>
 <a href="subject.html#65">[ subject ]</a>
 <a href="author.html#65">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>Thanks to everyone who has been keeping this discussion going, some very interesting perspectives have been raised and perhaps a little more background in the formation and objectives of the SMPTE Pink Noise calibration standard AHG might be in order.

As most of us are well aware, "Real Time Analysis" was once a primary audio measurement method which has largely been replaced by computer based techniques across most of academia and the broader audio industry over the course of the last couple of decades.

Integral to that measurement method was "Pink Noise" which because of its property of having equal power per log unit of bandwidth would ideally provide a "flat" trace when displayed on a 1/3 octave RTA.

Several people have asked why we would bother to standardize a pink noise signal, citing various issues with its suitability for use in more modern measurement approaches, which in turn brings into the debate the broad variety of modern measurement techniques, but that is getting beside the point and really is tangential to the work of SMPTE's Pink Noise AHG.

It is however, a matter of direct relevance to a couple of other groups which are actively investigating updated methods for measurement and calibration.

The fact remains that the Cinema industry has been somewhat slow on the uptake with the more modern measurement tools, many cinema systems are still aligned and calibrated using the old RTA methods for better or worse, and the matter of level calibration, even among those using MLS, and other DFT analysis methods for equalization and frequency response adjustment, is still most commonly performed using either a broad band pink noise or a band limited version and measured with an SPL meter.

So, returning to the pink noise signal itself- many existing standards such as the IEC 60268-1 mentioned below only provide guidelines for filtering and qualifying noise using quasi-peak meters, which were reasonable approaches to use at the time these standards were drafted, but using modern digital analysis tools has revealed a wider range of variance than was expected among signals which were believed to conform with these standards.

Specifically, the rms value and peak values were measures that were not always easily taken with traditional metering methods, sometimes requiring separate types of meter for peak (or quasi-peak) and average (or rms) value determination, and some of the shortcomings inherent in these metering methods has been demonstrated to account for some of the variances when so-called reference signals were digitally evaluated whereby the rms value is directly calculated by the statistical standard deviation, and the peak value can be numerically extracted without concern for meter ballistics or peak hold time constants.

It was felt that these analysis tools, along with modern DSP signal generation methods can provide us with an opportunity to constrain a standard reference signal in such a manner that these properties can be expected to have a much more consistent value, and that any calibrations made with such a signal could have a higher degree of confidence than was possible when crest factors and RMS values were not as precisely constrained.

We also hope that by going through this exercise, it can serve as an example; as the future brings to bear new test signals and methods for measurement and calibration, that those signals will also have a better chance of being properly specified in terms of specific parameter constraints from the onset.

We aren't out to do any massive alteration to existing practices- the more reputable pink noise signals that are widely available are not terribly out of whack with one another, so the hope is that our standard won't be such a significant change as to alter the calibration results in a major way, but instead we believe that narrowing in on a more consistent reference signal is worthy of standardization, even if it does come to mark the last era of real relevance for such a signal.

The specification currently being discussed establishes a target rms value which corresponds to that of a sine tone which is 20dB below FSD, or -23dB when referred to a full scale peak value.

Proper pink noise theoretically can have an infinite crest factor, but the peak swing of physical systems clearly place one bound on that, and the further constraints imposed in the pink filtering process seem to leave maximum peak values relating to a crest factor which typically lies between 10dB and 16dB above the rms value unless some extreme compression or clipping is used to reduce it beyond those levels.

In an effort to narrow the range of that variable, we are proposing a crest factor be bound to 12dB so that the reference signal can have an acknowledged and understood peak swing such that adjustments to the level would have a known and deterministic maximum value, and not induce clipping within those constrained levels.

Further discussion is needed in refining the tolerances for these parameters as well as those of the spectral content and out of band behavior, so these additional references and discussions are very valuable and I hope that they will continue.

Again many thanks for the lively discussion, let's keep it going!

-Pete Soper
Chair SMPTE TC25-SCC AHG for standardized calibration reference pink noise signal and file.

-----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 John Woodgate
Sent: Wednesday, July 17, 2013 10:41 AM
To: Working group on Measurement and equalization of sound systems in rooms
Subject: Re: [SC-04-08] AES-X215 B-Chain level measurements

In message 
<<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">5B9CF13FCBF0BD408B0F0A1F63FA94752A0EADC9 at ExDAG40-N1.hostallapps.net</A>>, 
dated Wed, 17 Jul 2013, Charlie Hughes <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">charlie at excelsior-audio.com</A>> 
writes:

>If the signal for measurements must be noise, I think there are 
>definite benefits to using shaped, band limited pink noise. Specifying 
>the noise to have the same spectral content as "average" program 
>material should minimize the over excitation of the HF section of 
>loudspeaker systems. Certainly ANSI/CEA-426-B as well as IEC 60268-1 
>have their "flavors" of noise. CEA should be issuing a new standard 
>shortly with an new flavor of noise, similar to IEC 60268 with 
>increased LF level.

I hope CEA will propose any new signal to IEC TC100 for inclusion in IEC 
60268-1. Conflicting standards help no-one, and lethargy is not an 
excuse.

The current IEC 60268-1 signal is not a noise signal but a blend of many 
speech and music signals. It is a 'long-term average', with the 
averaging time not defined. Any new signal should have a specified 
averaging time. Short-term average (less than 1 s) spectra of programme 
signals are significantly different from the long-term spectrum in the 
standard.
>
>The crest factor and probability density function of the noise should 
>also be specified. Work in SC-04-03 while pursuing AES2-2012 came to 
>the conclusion that a CF of 12 dB should work well for the test noise. 
>That reasoning was that with a lower CF, say 6 dB, when the noise was 
>filtered (via required HP filters or the internal crossover filters of 
>loudspeaker systems) the CF of the filter noise tended towards 12 dB.

I agree that 12 dB is reasonable. ANY filtering alters the crest factor, 
but when you get to crest factor 5, the big peaks occur so seldom that 
they normally have negligible effect. If you do hit one in a test and 
you can see that it corrupted the results, just run another test.
-- 
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
Why is the stapler always empty just when you want it?

John Woodgate, J M Woodgate and Asso...

Expand

This file was truncated for preview. Please download to view the full file.

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 Charlie Hughes 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3C5B9CF13FCBF0BD408B0F0A1F63FA94752A0EAF89%40ExDAG40-N1.hostallapps.net%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">charlie at excelsior-audio.com
 </A> 
 Wed Jul 17 14:46:57 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000075.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000061.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#66">[ date ]</a>
 <a href="thread.html#66">[ thread ]</a>
 <a href="subject.html#66">[ subject ]</a>
 <a href="author.html#66">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>Calm down big boy. I think you're making an erroneous assumption that the current CEA draft standard and IEC 60268-1 (or any other in the 60268 series) are in conflict. They are not. The test signal to which I referred that is in the draft of a new CEA standard is used for a test which is not specified in any IEC standard of which I am aware. Therefore the two standards should not be in conflict.

At the appropriate time, once the draft has been approved by CEA, the standard will be sent to ANSI for inclusion.  At that point we plan to submit it to TC100 for consideration.  Hopefully it can be adopted as another in the 60268 series.

Charlie Hughes
Excelsior Audio Design & Services, LLC
Gastonia, NC
+1 704.675.5435 (tel)     +1 704.678.6570 (mobile)
+1 704.675.5436 (fax)
www.excelsior-audio.com
 
Copyright 2013 - Excelsior Audio Design & Services, LLC

-----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 John Woodgate
Sent: Wednesday, 17 July, 2013 1:41 PM
To: Working group on Measurement and equalization of sound systems in rooms
Subject: Re: [SC-04-08] AES-X215 B-Chain level measurements

I hope CEA will propose any new signal to IEC TC100 for inclusion in IEC 60268-1. Conflicting standards help no-one, and lethargy is not an excuse.

</PRE>

<HR>
 <UL>
 
	<LI>Previous message: <A HREF="000075.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000061.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#66">[ date ]</a>
 <a href="thread.html#66">[ thread ]</a>
 <a href="subject.html#66">[ subject ]</a>
 <a href="author.html#66">[ 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>

Expand

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 John Woodgate 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3Ck4g0koMQKx5RFwgH%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">jmw at jmwa.demon.co.uk
 </A> 
 Wed Jul 17 15:54:24 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000065.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000068.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#67">[ date ]</a>
 <a href="thread.html#67">[ thread ]</a>
 <a href="subject.html#67">[ subject ]</a>
 <a href="author.html#67">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">2BE563BCBE473946A8E72AE261D4F64BE78CF591 at XCHG2.ms.msli.com</A>>, 
dated Wed, 17 Jul 2013, Pete Soper <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">psoper at meyersound.com</A>> writes:

>
>So, returning to the pink noise signal itself- many existing standards 
>such as the IEC 60268-1 mentioned below only provide guidelines for 
>filtering and qualifying noise using quasi-peak meters,

The references in this discussion to IEC 60268-1 refer to the Simulated 
Programme Signal, a weighted noise signal, not to anything about 
quasi-peak meters.
-- 
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
Why is the stapler always empty just when you want it?

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
</PRE>

<HR>
 <UL>
 
	<LI>Previous message: <A HREF="000065.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000068.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#67">[ date ]</a>
 <a href="thread.html#67">[ thread ]</a>
 <a href="subject.html#67">[ subject ]</a>
 <a href="author.html#67">[ 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>

Expand

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 Pete Soper 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3C2BE563BCBE473946A8E72AE261D4F64BE78CFAD0%40XCHG2.ms.msli.com%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">psoper at meyersound.com
 </A> 
 Wed Jul 17 16:12:48 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000067.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000069.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#68">[ date ]</a>
 <a href="thread.html#68">[ thread ]</a>
 <a href="subject.html#68">[ subject ]</a>
 <a href="author.html#68">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>I agree that in the section describing the simulated programme signal measurement is prescribed as being done with a true rms meter, however that would not provide crest factor information, but dynamic performance appraisals involving tone bursts and weighted noise is discussed in Appendix A which does in fact refer to quasi-peak meters.

-----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 John Woodgate
Sent: Wednesday, July 17, 2013 2:54 PM
To: Working group on Measurement and equalization of sound systems in rooms
Subject: Re: [SC-04-08] AES-X215 B-Chain level measurements

In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">2BE563BCBE473946A8E72AE261D4F64BE78CF591 at XCHG2.ms.msli.com</A>>, 
dated Wed, 17 Jul 2013, Pete Soper <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">psoper at meyersound.com</A>> writes:

>
>So, returning to the pink noise signal itself- many existing standards 
>such as the IEC 60268-1 mentioned below only provide guidelines for 
>filtering and qualifying noise using quasi-peak meters,

The references in this discussion to IEC 60268-1 refer to the Simulated 
Programme Signal, a weighted noise signal, not to anything about 
quasi-peak meters.
-- 
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
Why is the stapler always empty just when you want it?

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
_______________________________________________
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>>

NOTICE: This email may contain confidential information. Please see <A HREF="http://www.meyersound.com/confidential/">http://www.meyersound.com/confidential/</A> for our complete policy.
</PRE>

<HR>
 <UL>
 
	<LI>Previous message: <A HREF="000067.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000069.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#68">[ date ]</a>
 <a href="thread.html#68">[ thread ]</a>
 <a href="subject.html#68">[ subject ]</a>
 <a href="author.html#68">[ 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>

Expand

Options

Copy Download Link

<TITLE> [SC-04-08] AES-X215 B-Chain level measurements
 </TITLE>
 
 
 
 
 pre {
 white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */
 }
 
 
 
 
 
 
 <H1>[SC-04-08] AES-X215 B-Chain level measurements</H1>
 Bob Walker 
 <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20AES-X215%20B-Chain%20level%20measurements&In-Reply-To=%3C51E7F524.9020209%40rlsw.eclipse.co.uk%3E" TITLE="[SC-04-08] AES-X215 B-Chain level measurements">bob at rlsw.eclipse.co.uk
 </A> 
 Thu Jul 18 08:01:08 MDT 2013
 <UL>
 <LI>Previous message: <A HREF="000068.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI>Next message: <A HREF="000070.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#69">[ date ]</a>
 <a href="thread.html#69">[ thread ]</a>
 <a href="subject.html#69">[ subject ]</a>
 <a href="author.html#69">[ author ]</a>
 </LI>
 </UL>
 <HR> 

<PRE>I confess myself to be a little confused here by this discussion of 
"test signals".

My recollection is that the origin of these 'cinema' measurement 
problems lies in the use of any sort of steady-state response.

It is generally well known, and has been known for many years, that the 
steady-state response may not (does not?) relate very well to the human 
perception of audio. In the BBC, we established that, and the 
inappropriateness of band-limited equalisation, at least 30 years ago.

It might be argued that the appropriate remedy for inadequate sound 
quality is to correct the responses in the room by proper loudspeaker 
and room acoustic design. That is certainly the appropriate response for 
professional listening rooms and studios/control rooms. It appears not 
to be possible within the constraints of the cinema industry.

In my view, the problem has arisen from the inappropriate use of 
band-selective equalisation in an attempt to first standardise and then 
'correct' room responses. Accordingly, at the outset of my involvement 
with this group, I suggested that some sort of simple analyser might be 
developed that automatically (or semi-automatically) selected some part 
of the room impulse response to derive some sort of time-limited 
response. In that way, a objective result might be obtained that was 
more like the human perception response .

Clearly (and theoretically), a system impulse response does not depend 
directly on the excitation signal, though admittedly there are 
substantial secondary considerations in the choice of test signal.

I have been working on such a demonstration system and plan to present 
it at the forthcoming Reproduced Sound conference in November. This has 
been developed on a cross-platform basis, and should be available for 
Windows, Linux, Apple and Android platforms. The immediate objective of 
this test system is to allow the assessment and maybe optimisation of 
various measurement parameters.

Ultimately, it might be possible to implement a much simplified version, 
for use by non-expert technicians in cinemas and production rooms for 
example as an 'app', to be interposed between a measurement microphone 
and a RT analyser. It is my expectation that any device with reasonable 
digital audio I/O would have adequate response uniformity to be 
acceptable for this application. Accuracy of absolute level is less of 
an issue and/or can be determined separately.

The development is currently at an early stage and I am not prepared to 
release it at present, but after November I would be happy to provide 
source code to anyone that feels like evaluating it. I have not tried 
the 'cross-platform' bit yet, so the only executable available would 
probably be only for Linux.

Bob
-------------------------------------------------------
Bob Walker, 28 Woodcote Hurst, Epsom, KT18 7DT. Tel: +44 (0)1372 740384. 
Mobile: 07752 569014
</PRE>

<HR>
 <UL>
 
	<LI>Previous message: <A HREF="000068.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
	<LI>Next message: <A HREF="000070.html">[SC-04-08] AES-X215 B-Chain level measurements
</A></li>
 <LI> Messages sorted by: 
 <a href="date.html#69">[ date ]</a>
 <a href="thread.html#69">[ thread ]</a>
 <a href="subject.html#69">[ subject ]</a>
 <a href="author.html#69">[ 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>

Expand