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Documents Folder Title Following special characters are not supported: \ / ? % * : | " < > Privacy Public All Members My Connections Only Me Cancel Create 000140.html 4 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>John Woodgate</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3CuaMWsbArMgbSFwuL%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">jmw at jmwa.demon.co.uk </A><BR> <I>Mon Oct 28 00:24:43 MDT 2013</I> <P><UL> <LI>Previous message: <A HREF="000139.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000142.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#140">[ date ]</a> <a href="thread.html#140">[ thread ]</a> <a href="subject.html#140">[ subject ]</a> <a href="author.html#140">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">BLU0-SMTP209E62C1258A37181CFF2FCC080 at phx.gbl</A>>, dated Mon, 28 Oct 2013, Thomas Lagö <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">thomaslago at msn.com</A>> writes: ><i>2. A "pink noise generator" for any device that per definition will be </I>><i>non-synchronised. The latter WILL lose all its "MLS unique properties". </I> Which properties? It does not lose its predictability, which is a BIG asset, and its crest factor, to which perhaps more importance is given than is justified, because we are usually talking about crest factors between 3 and 4. You have to measure for quite a long time to find out if the crest factor is 4, because of the low probability of the highest possible peak value. It's actually easier and quicker to find the clipping level of the source and assume that the signal can very occasionally hit it. ><i>Both can be made pink or white or "any shape" in frequency domain. </I> Indeed. ><i>Since it sounds like we must develop a "pink noise generator" that can </I>><i>be used by any system, category "1" cannot be considered. Is that a </I>><i>correct understanding? </I> Yes, that is the proposal, prompted by many reports of differences between supposedly equivalent noise sources using different techniques and implementations. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk If dictionaries were correct, we would only need one, because they would all give the same information. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000139.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000142.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#140">[ date ]</a> <a href="thread.html#140">[ thread ]</a> <a href="subject.html#140">[ subject ]</a> <a href="author.html#140">[ 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><br> Expand 000141.html 3 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>John Woodgate</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3CnKXUYJBGRgbSFwOC%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">jmw at jmwa.demon.co.uk </A><BR> <I>Mon Oct 28 00:29:26 MDT 2013</I> <P><UL> <LI>Previous message: <A HREF="000144.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000135.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#141">[ date ]</a> <a href="thread.html#141">[ thread ]</a> <a href="subject.html#141">[ subject ]</a> <a href="author.html#141">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">EA3E0F66-171C-4587-A1F2-517A736566B4 at meyersound.com</A>>, dated Sun, 27 Oct 2013, Pete Soper <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">psoper at meyersound.com</A>> writes: ><i>"Linear Time Invariant" </I> Thanks. We have somewhat 'quasi' linearity; do we always have time invariance in the context of performance assessment? Of course a system and its environment is not time invariant in general - occupation levels vary and so do climatic conditions. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk If dictionaries were correct, we would only need one, because they would all give the same information. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000144.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000135.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#141">[ date ]</a> <a href="thread.html#141">[ thread ]</a> <a href="subject.html#141">[ subject ]</a> <a href="author.html#141">[ 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><br> Expand 000142.html 9 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>Thomas Lagö</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3CBLU0-SMTP80EA574E085B8E2EBDC89BCC080%40phx.gbl%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">thomaslago at msn.com </A><BR> <I>Mon Oct 28 00:41:51 MDT 2013</I> <P><UL> <LI>Previous message: <A HREF="000140.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000143.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#142">[ date ]</a> <a href="thread.html#142">[ thread ]</a> <a href="subject.html#142">[ subject ]</a> <a href="author.html#142">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>Without a sync, it will lose its predictability. It is ONLY for the "system" that knows the starting (sync)n of the signal that it is predictable. This is widely used in telecom! I am attaching some more comments: Pink Noise Generator Thoughts LTI systems mean that they must be linear but also time invariant. This is especially difficult for the low frequency part in rooms. When I developed my RT60 system (1980) using a synchronized MLS signal, Per Bruel could not believe how stable the calculation was even at 50 Hz. The time variability is often neglected but MUST be considered! It is LTI systems in "system theory". The two signal generator groups exist: 1. Synchronized MLS like MLSSA. 2. A "pink noise generator" for any device that per definition will be non-synchronized. No sync (it is not the same “device” that analyze and send the test signal. MLSSA must use its own test signal for the algorithm to work. My approach to sync and correlation was even more efficient than MLSSA and developed before!) The latter approach WILL lose all its " unique MLS correlation properties" without a sync. Both can be made pink or white or "any shape" in frequency domain. Since it sounds like we must develop a "pink noise generator" that can be used by any system, category "1" cannot be considered. Is that a correct understanding? Since we cannot utilize the MLS properties, why use it then? Here comes some food for though: · An MLS sequence is deterministic and a filter shaping of the sinc-spectra can be defined. Hence, there is no doubt what the properties are. That is good! · For LTI systems, the signal generator will NOT change the result but WILL impact averaging (variance) and demand on amplifiers/speakers (crest factor). We all know that the results can change. This then tells us that the system is not as linear as we assume it to be. Using one generator type only will not reveal this in detail but using multiple types and comparing results WILL reveal the non-linearities (or variability) and where in frequency domain they exist, if they exist. This is something I often use: use multiple methods and compare results! Equal results, I am done. Different, more work to follow! · If a signal generator has ”random characteristics” we must average to compensate for the variability in the generator PLUS the variability in the room. A synchronized system only needs to consider the room since the generator has no variance. This ”challenge” was a big problem with the B&K RASTI system that used a random generator and the averaging time for the generator variance was very long and then the ”Rapid” part became wrong. The B&K system is now obsolete. I showed this problem using a test church (200 seats) many years back and presented the results at AES in St. Petersburg, Russia. These two reasons for averaging must be understood. Since we cannot synchronize the generator we must bite the bulled in regards to averaging. · When using an MLS (like MLSSA), a correlation approach is used. If the length is too short, the impulse response will wrap. Even for a non-synchronized signal, I would use a rather long sequence making sure that it cannot ”wrap” within the room’s RT60. I used 10 seconds but maybe something shorter could be used for these applications (movie theatres). · What do I suggest? o One well defined random signal with a pink noise spectrum using an MLS sequence as the foundation. All of this is mathematically explained and can be repeated exactly. Crest, variance and spectra can be calculated and will be 100% defined IF the same sequence is used. That should be stated. The length must be ”long enough.” o Using ”any” random generator with a known spectrum, crest factor and variance. The results should be compared. If ”equal” within the ”accuracy needed” the result is okay. o This process can be automated and made easy. By using two ”different approaches” we will know if the system is LTI enough or not! If we mix the LTI challenges with the room’s response it is hard to know why there are challenges. With this approach it is possible to sort them into categories. o For an LTI system, the system is NOT dependent on signal generator. Since we have challenges, the system is not fully LTI! On Oct 28, 2013, at 7:24 AM, John Woodgate <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">jmw at jmwa.demon.co.uk</A>> wrote: ><i> In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">BLU0-SMTP209E62C1258A37181CFF2FCC080 at phx.gbl</A>>, dated Mon, 28 Oct 2013, Thomas Lagö <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">thomaslago at msn.com</A>> writes: </I>><i> </I>>><i> 2. A "pink noise generator" for any device that per definition will be non-synchronised. The latter WILL lose all its "MLS unique properties". </I>><i> </I>><i> Which properties? It does not lose its predictability, which is a BIG asset, and its crest factor, to which perhaps more importance is given than is justified, because we are usually talking about crest factors between 3 and 4. You have to measure for quite a long time to find out if the crest factor is 4, because of the low probability of the highest possible peak value. It's actually easier and quicker to find the clipping level of the source and assume that the signal can very occasionally hit it. </I>><i> </I>>><i> Both can be made pink or white or "any shape" in frequency domain. </I>><i> </I>><i> Indeed. </I>><i> </I>>><i> Since it sounds like we must develop a "pink noise generator" that can be used by any system, category "1" cannot be considered. Is that a correct understanding? </I>><i> </I>><i> Yes, that is the proposal, prompted by many reports of differences between supposedly equivalent noise sources using different techniques and implementations. </I>><i> -- </I>><i> OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk </I>><i> If dictionaries were correct, we would only need one, because they would all </I>><i> give the same information. </I>><i> John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </I>><i> _______________________________________________ </I>><i> SC-04-08 mailing list </I>><i> <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">SC-04-08 at standards.aes.org</A> </I>><i> <<A HREF="http://standards.aes.org/sc.cfm?ID=91">http://standards.aes.org/sc.cfm?ID=91</A>> </I>><i> </I> </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000140.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000143.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#142">[ date ]</a> <a href="thread.html#142">[ thread ]</a> <a href="subject.html#142">[ subject ]</a> <a href="author.html#142">[ 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><br> Expand 000143.html 7 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>John Woodgate</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3Clb9E8rCvrhbSFweY%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">jmw at jmwa.demon.co.uk </A><BR> <I>Mon Oct 28 02:06:07 MDT 2013</I> <P><UL> <LI>Previous message: <A HREF="000142.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000144.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#143">[ date ]</a> <a href="thread.html#143">[ thread ]</a> <a href="subject.html#143">[ subject ]</a> <a href="author.html#143">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">BLU0-SMTP80EA574E085B8E2EBDC89BCC080 at phx.gbl</A>>, dated Mon, 28 Oct 2013, Thomas Lagö <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">thomaslago at msn.com</A>> writes: ><i>Without a sync, it will lose its predictability. It is ONLY for the </I>><i>"system" that knows the starting (sync)n of the signal that it is </I>><i>predictable. This is widely used in telecom! I am attaching some more </I>><i>comments: </I> I think we are using different definitions of 'predictability'. See below. ><i> </I>><i> </I>[snip] ><i> </I>><i>· An MLS sequence is deterministic and a filter shaping of the </I>><i>sinc-spectra can be defined. Hence, there is no doubt what the </I>><i>properties are. That is good! </I> Agreed. ><i> </I>><i>· For LTI systems, the signal generator will NOT change the </I>><i>result but WILL impact averaging (variance) and demand on </I>><i>amplifiers/speakers (crest factor). We all know that the results can </I>><i>change. This then tells us that the system is not as linear as we </I>><i>assume it to be. </I> I'm not sure that this conclusion is safe. ><i>Using one generator type only will not reveal this in detail but using </I>><i>multiple types and comparing results WILL reveal the non-linearities </I>><i>(or variability) and where in frequency domain they exist, if they </I>><i>exist. This is something I often use: use multiple methods and compare </I>><i>results! Equal results, I am done. Different, more work to follow! </I> I think that for the assessment of installed sound systems, the use of several methods is impracticable. ><i> </I>[snip] ><i> Even for a non-synchronized signal, I would use a rather long sequence </I>><i>making sure that it cannot ”wrap” within the room’s RT60. I used </I>><i>10 seconds but maybe something shorter could be used for these </I>><i>applications (movie theatres). </I> 10 s might be enough. I'm not thinking of the strict technical requirements but what the signal sounds like. if it doesn't sound like noise (and it won't if it recurs too often) there will be a credibility gap. ><i> </I>><i>· What do I suggest? </I>><i> </I>><i>o One well defined random signal with a pink noise spectrum using an </I>><i>MLS sequence as the foundation. All of this is mathematically explained </I>><i>and can be repeated exactly. Crest, variance and spectra can be </I>><i>calculated and will be 100% defined IF the same sequence is used. </I> That's what I mean by 'predictable'. ><i>That should be stated. The length must be ”long enough.” </I> Agreed. In the literature are descriptions of sequences tens of minutes long. We do not want or need that. ><i> </I>><i>o Using ”any” random generator with a known spectrum, crest </I>><i>factor and variance. The results should be compared. If ”equal” </I>><i>within the ”accuracy needed” the result is okay. </I> Yes, but the devil is in the 'known'; it's really quite difficult to make an accurate measurement of r.m.s. value/variance of the noise from some type of source. ><i> </I>><i>o This process can be automated and made easy. </I> I wish I could share your confidence. ><i>By using two ”different approaches” we will know if the system is </I>><i>LTI enough or not! If we mix the LTI challenges with the room’s </I>><i>response it is hard to know why there are challenges. With this </I>><i>approach it is possible to sort them into categories. </I>><i> </I>><i>o For an LTI system, the system is NOT dependent on signal generator. </I>><i>Since we have challenges, the system is not fully LTI! </I>><i> </I>Surely differences between signal generators are not irrelevant? Difference may be in how the spectrum tails off at the band limits, the real r.m.s. value and crest factor and the amplitude-probability distribution. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk If dictionaries were correct, we would only need one, because they would all give the same information. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000142.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000144.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#143">[ date ]</a> <a href="thread.html#143">[ thread ]</a> <a href="subject.html#143">[ subject ]</a> <a href="author.html#143">[ 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><br> Expand 000144.html 8 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>Thomas Lagö</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3CBLU0-SMTP1048F2FF9CFA76EDEB2CCACC080%40phx.gbl%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">thomaslago at msn.com </A><BR> <I>Mon Oct 28 02:23:43 MDT 2013</I> <P><UL> <LI>Previous message: <A HREF="000143.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000141.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#144">[ date ]</a> <a href="thread.html#144">[ thread ]</a> <a href="subject.html#144">[ subject ]</a> <a href="author.html#144">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>John, good comments. See my comments to your comments below (in red). -Thomas On Oct 28, 2013, at 9:06 AM, John Woodgate <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">jmw at jmwa.demon.co.uk</A>> wrote: ><i> In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">BLU0-SMTP80EA574E085B8E2EBDC89BCC080 at phx.gbl</A>>, dated Mon, 28 Oct 2013, Thomas Lagö <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">thomaslago at msn.com</A>> writes: </I>><i> </I>>><i> Without a sync, it will lose its predictability. It is ONLY for the "system" that knows the starting (sync)n of the signal that it is predictable. This is widely used in telecom! I am attaching some more comments: </I>><i> </I>><i> I think we are using different definitions of 'predictability'. See below. </I>>><i> </I>>><i> </I>><i> [snip] </I>>><i> </I>>><i> · An MLS sequence is deterministic and a filter shaping of the sinc-spectra can be defined. Hence, there is no doubt what the properties are. That is good! </I>><i> </I>><i> Agreed. </I>>><i> </I>>><i> · For LTI systems, the signal generator will NOT change the result but WILL impact averaging (variance) and demand on amplifiers/speakers (crest factor). We all know that the results can change. This then tells us that the system is not as linear as we assume it to be. </I>><i> </I>><i> I'm not sure that this conclusion is safe. For any LTI system, the system (impulse response or FRF) is not dependent on the input signal given that the signal excite the system (SNR and not signal class). </I>><i> </I>>><i> Using one generator type only will not reveal this in detail but using multiple types and comparing results WILL reveal the non-linearities (or variability) and where in frequency domain they exist, if they exist. This is something I often use: use multiple methods and compare results! Equal results, I am done. Different, more work to follow! </I>><i> </I>><i> I think that for the assessment of installed sound systems, the use of several methods is impracticable. I hear you but this is a very safe and excellent method and will reveal how LTI the system is. </I>>><i> </I>><i> [snip] </I>>><i> Even for a non-synchronized signal, I would use a rather long sequence making sure that it cannot ”wrap” within the room’s RT60. I used 10 seconds but maybe something shorter could be used for these applications (movie theatres). </I>><i> </I>><i> 10 s might be enough. I'm not thinking of the strict technical requirements but what the signal sounds like. if it doesn't sound like noise (and it won't if it recurs too often) there will be a credibility gap. Agree! </I>>><i> </I>>><i> · What do I suggest? </I>>><i> </I>>><i> o One well defined random signal with a pink noise spectrum using an MLS sequence as the foundation. All of this is mathematically explained and can be repeated exactly. Crest, variance and spectra can be calculated and will be 100% defined IF the same sequence is used. </I>><i> </I>><i> That's what I mean by 'predictable'. Okay and agree. </I>><i> </I>>><i> That should be stated. The length must be ”long enough.” </I>><i> </I>><i> Agreed. In the literature are descriptions of sequences tens of minutes long. We do not want or need that. No, it is not needed but if the length is too short, the length can also be "heard". </I>>><i> </I>>><i> o Using ”any” random generator with a known spectrum, crest factor and variance. The results should be compared. If ”equal” within the ”accuracy needed” the result is okay. </I>><i> </I>><i> Yes, but the devil is in the 'known'; it's really quite difficult to make an accurate measurement of r.m.s. value/variance of the noise from some type of source. This signal is ONLY for comparison and NOT for the reference test! Is the system LTI enough? </I>>><i> </I>>><i> o This process can be automated and made easy. </I>><i> </I>><i> I wish I could share your confidence. I know it can be automated :-) </I>><i> </I>>><i> By using two ”different approaches” we will know if the system is LTI enough or not! If we mix the LTI challenges with the room’s response it is hard to know why there are challenges. With this approach it is possible to sort them into categories. </I>>><i> </I>>><i> o For an LTI system, the system is NOT dependent on signal generator. Since we have challenges, the system is not fully LTI! </I>>><i> </I>><i> Surely differences between signal generators are not irrelevant? Difference may be in how the spectrum tails off at the band limits, the real r.m.s. value and crest factor and the amplitude-probability distribution. Well, if that is happening the system is not LTI, that is for sure :-) (For non-LTI, the system is input signal dependent). </I>><i> -- </I>><i> OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk </I>><i> If dictionaries were correct, we would only need one, because they would all </I>><i> give the same information. </I>><i> John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </I>><i> _______________________________________________ </I>><i> SC-04-08 mailing list </I>><i> <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">SC-04-08 at standards.aes.org</A> </I>><i> <<A HREF="http://standards.aes.org/sc.cfm?ID=91">http://standards.aes.org/sc.cfm?ID=91</A>> </I> </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000143.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000141.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#144">[ date ]</a> <a href="thread.html#144">[ thread ]</a> <a href="subject.html#144">[ subject ]</a> <a href="author.html#144">[ 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><br> Expand 000145.html 10 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>Ben Kok</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3CDUB405-EAS265A8A255B897AA7A672F50E60F0%40phx.gbl%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">bk-ac at live.nl </A><BR> <I>Sun Oct 27 14:57:23 MDT 2013</I> <P><UL> <LI>Previous message: <A HREF="000133.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000146.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#145">[ date ]</a> <a href="thread.html#145">[ thread ]</a> <a href="subject.html#145">[ subject ]</a> <a href="author.html#145">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>Thomas, The idea is to use MLS (or another algorithm) to generate a test signal suited to measure quasi steady state SPL and RTA spectrum. Measuring impulse responses is a complete different issue. For measuring IR your restrictions apply. The reasoning for suggesting MLS as an alternative for "true" noise are: - like with a noise signal, all frequencies are there all the time, albeit with a white spectrum, so (pink) spectrum shaping is required - for the tests under consideration, crest factor only is a consideration if it might drive the system into non-linearity; so a low crest factor is preferred; in the NY meeting we considered a maximum of 12 dB as being acceptable - each MLS sequence is identical, so when a full sequence is measured, the measurement reproduces perfectly; this means that when the sequence length is the same as the settling time of the meter the highest reproducibility is achieved. - the frequency density/ resolution is directly related to the MLS sequence length, with a sequence of 1s (SLM at "slow") the frequency spacing is 1 Hz, which should give sufficient density even at low frequencies. If the working group considers this density insufficient and a longer sequence is required, we need to fall back to Leq measurements, which might not be available on all the devices currently used by cinema technicians. - out of band energy also is a consideration; we intend to prescribe high and low roll-off filters with slope and cut-off frequencies to be decided upon; this also will deal with any DC component in the MLS algorithm. Hope this clarifies a bit what we want to do, your input is highly appreciated. Ben pls. reply to <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">Ben at benkok.com</A> ><i> Op 27 okt. 2013 om 21:21 heeft "Thomas Lagö" <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">thomaslago at msn.com</A>> het volgende geschreven: </I>><i> </I>><i> Dear Peter, </I>><i> </I>><i> Peter, </I>><i> </I>><i> Thanks for your prompt response. Your questions and remarks are tricky and clever. I will try to handle part of it right now. </I>><i> </I>><i> An MLS with a sync signal will NOT behave like a random source since it is a deterministic signal. Without a sync, an MLS behaves "random" and then many of your comments are valid. WITH a sync signal, the length must be longer than the impulse response of interested and together with the bandwidth needed, this sets the clock frequency and hence the length as well. A filtering can easily become "inherent" in the sequence since both the LMS and the filtering follows an FIR filter structure. I have proven this in my designs. For a synchronised signal and a linear system, this becomes less important but crest factor and "out of band" signals will change by the filtering. The basic MLS signal has a "sinc" shape in frequency domain. For LTI systems, the output response is NOT related to the input signal, given that we cover bandwidth and dynamic range properly. </I>><i> </I>><i> For a non-synchronised signal, we enter a completely different domain where we are trying to "emulate" a random signal. Then, length and filtering has a completely different meaning. </I>><i> </I>><i> We need to define how "linear" we are. Do we assume that distortion is reasonably small or not? If not, a random signal will give an LMS estimate and THEN all statistical parameters WILL impact the results since the input signal impacts the result for a non-linear systems but does not for a linear system. </I>><i> </I>><i> Did I manage to explain the difference in signal generator approaches in regards to linear and non-linear systems? Do we assume a synchronised or non-synchronized MLS? For speakers, I always use a synchronized MLS! I might compare with a "random" but my MLS signal is my reference! </I>><i> </I>><i> Best regards, </I>><i> Thomas Lagö </I>><i> </I>>><i> On Oct 27, 2013, at 8:52 PM, "Peter Mapp" <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">peter at petermapp.com</A>> wrote: </I>>><i> </I>>><i> Will do when back in uk. Two of the software versions include ability to pink shape the signal. I have B&K filter for other expt or ( it might be interesting to also use your filter but as you already have & my time at the moment is a little limited, perhaps you could do that - at least in the first instance. </I>>><i> </I>>><i> Perhaps we should explain to Thomas that we are not intending to use the IR potential of MLS, but merely to use as a consistent & repeatable signal signal instead of pseudorandom pink noise. </I>>><i> </I>>><i> Rgs </I>>><i> </I>>><i> Peter </I>>><i> </I>>><i> Sent from my iPhone </I>>><i> </I>>>><i> On 27 Oct 2013, at 19:30, "John Woodgate" <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">jmw at jmwa.demon.co.uk</A>> wrote: </I>>>><i> </I>>>><i> In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">2498EF26-E564-487B-A768-0C110D82A366 at petermapp.com</A>>, dated Sun, 27 Oct 2013, Peter Mapp <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">peter at petermapp.com</A>> writes: </I>>>><i> </I>>>>><i> I have 3 software versions of an MLS signal. Can verify that filtering affects the crest factor _ though don't have results to hand. I could re measure with a known pink filter if this would assist. </I>>>><i> </I>>>><i> If you have .wav files (with at least one full sequence if not too huge; there is one with a 40 minute recurrence period in the literature), please send them to me. If they are huge, can you please send .wav files on a CD? This, of course, in addition to any measurements you conduct. </I>>>><i> </I>>>><i> One thing isn't clear; do you have the 'known pink filter' or do you want the circuit of mine? </I>>>><i> -- </I>>>><i> OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk </I>>>><i> If dictionaries were correct, we would only need one, because they would all </I>>>><i> give the same information. </I>>>><i> John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </I>>>><i> _______________________________________________ </I>>>><i> SC-04-08 mailing list </I>>>><i> <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">SC-04-08 at standards.aes.org</A> </I>>>><i> <<A HREF="http://standards.aes.org/sc.cfm?ID=91">http://standards.aes.org/sc.cfm?ID=91</A>> </I>>><i> </I>>><i> _______________________________________________ </I>>><i> SC-04-08 mailing list </I>>><i> <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">SC-04-08 at standards.aes.org</A> </I>>><i> <<A HREF="http://standards.aes.org/sc.cfm?ID=91">http://standards.aes.org/sc.cfm?ID=91</A>> </I>><i> </I>><i> _______________________________________________ </I>><i> SC-04-08 mailing list </I>><i> <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">SC-04-08 at standards.aes.org</A> </I>><i> <<A HREF="http://standards.aes.org/sc.cfm?ID=91">http://standards.aes.org/sc.cfm?ID=91</A>> </I>><i> </I>><i> </I>><i> _______________________________________________________ </I>><i> Unlimited Disk, Data Transfer, PHP/MySQL Domain Hosting </I>><i> <A HREF="http://www.doteasy.com">http://www.doteasy.com</A> </I></PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000133.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000146.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#145">[ date ]</a... Expand This file was truncated for preview. Please download to view the full file. 000146.html 4 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>John Woodgate</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3Cn%2BSUFIDNxkcSFw1Q%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">jmw at jmwa.demon.co.uk </A><BR> <I>Thu Oct 31 06:25:49 MDT 2013</I> <P><UL> <LI>Previous message: <A HREF="000145.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000147.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#146">[ date ]</a> <a href="thread.html#146">[ thread ]</a> <a href="subject.html#146">[ subject ]</a> <a href="author.html#146">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">DUB405-EAS265A8A255B897AA7A672F50E60F0 at phx.gbl</A>>, dated Sun, 27 Oct 2013, Ben Kok <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">bk-ac at live.nl</A>> writes: ><i> so a low crest factor is preferred; in the NY meeting we considered a </I>><i>maximum of 12 dB as being acceptable </I> I would point out that to eliminate a source of non-repeatability, the crest factor should be closely controlled. But measuring higher crest factors, even a factor of 4, may take a relatively long time in order to ensure that at least one rare peak of 4 times the r.m.s. value actually occurs. For higher crest factors, the required observation time becomes very long indeed. I think that the analogue sum of four MLS signals (the same sequence but with different delays) has a predictable crest factor of 4, but I am not sure what effects the necessary low-pass filter (to get Gaussian white noise) and the 'pinking' filter have on the crest factor of the final signal. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Nondum ex silvis sumus John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000145.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000147.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#146">[ date ]</a> <a href="thread.html#146">[ thread ]</a> <a href="subject.html#146">[ subject ]</a> <a href="author.html#146">[ 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><br> Expand 000147.html 6 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>Glenn Leembruggen</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3C000001cedeb9%24f09a4080%24d1cec180%24%40acousticdirections.com%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">glenn at acousticdirections.com </A><BR> <I>Mon Nov 11 01:42:17 MST 2013</I> <P><UL> <LI>Previous message: <A HREF="000146.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000148.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#147">[ date ]</a> <a href="thread.html#147">[ thread ]</a> <a href="subject.html#147">[ subject ]</a> <a href="author.html#147">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>Hi All After our meeting in NY, I did some simulations using Matlab of white and pink MLS crest factors. When I applied a 1000 point FIR filter with 1/sqrt( f), to the raw MLS signal to bring it to a pink spectrum, I found that the crest factor 0f a ! sec MLS increased from 0 dB when unfiltered to 12.2 dB with pink filtering. I believe Pete Soper found similar results. I suspect that in this context, some of the defined benefits of the MLS signal aren’t as strong as we first thought. Cheers Glenn Glenn Leembruggen Acoustic Directions Pty Ltd 14 65-67 Crystal St Petersham 2049 Australia PO Box 205 Summer Hill 2130 tel: +61 2 9568 4684 fax: +61 2 9572 8939 mob: +61 418 207 085 The information contained in this e-document and any file attachments is confidential to all parties except the intended recipients. If you are not an intended recipient you have received this document in error and are prohibited from disclosing or using any of the information contained. We would be grateful if you would advise us of such errors immediately by return email. Thank you. -----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: Thursday, 31 October 2013 11:26 PM To: Working group on Measurement and equalization of sound systems in rooms Subject: Re: [SC-04-08] Using pink MLS instead of conventional pink nose In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">DUB405-EAS265A8A255B897AA7A672F50E60F0 at phx.gbl</A>>, dated Sun, 27 Oct 2013, Ben Kok <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">bk-ac at live.nl</A>> writes: ><i> so a low crest factor is preferred; in the NY meeting we considered a </I>><i>maximum of 12 dB as being acceptable </I> I would point out that to eliminate a source of non-repeatability, the crest factor should be closely controlled. But measuring higher crest factors, even a factor of 4, may take a relatively long time in order to ensure that at least one rare peak of 4 times the r.m.s. value actually occurs. For higher crest factors, the required observation time becomes very long indeed. I think that the analogue sum of four MLS signals (the same sequence but with different delays) has a predictable crest factor of 4, but I am not sure what effects the necessary low-pass filter (to get Gaussian white noise) and the 'pinking' filter have on the crest factor of the final signal. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Nondum ex silvis sumus 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>> </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000146.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000148.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#147">[ date ]</a> <a href="thread.html#147">[ thread ]</a> <a href="subject.html#147">[ subject ]</a> <a href="author.html#147">[ 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><br> Expand 000148.html 7 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>Thomas Lagö</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3CBLU0-SMTP115E225F717AA96C32CE770CCFF0%40phx.gbl%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">thomaslago at msn.com </A><BR> <I>Mon Nov 11 01:52:08 MST 2013</I> <P><UL> <LI>Previous message: <A HREF="000147.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000149.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#148">[ date ]</a> <a href="thread.html#148">[ thread ]</a> <a href="subject.html#148">[ subject ]</a> <a href="author.html#148">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>Hi All, The key benefits of MLS are being lost if the "sync approach" is not used. Filtering must change the crest factor. The key benefit (in my opinion) of using an MLS would be that you can define how it should be created (length etc) and the FIR filter is known. That makes the noise "known". BR, Thomas On Nov 11, 2013, at 9:42 AM, "Glenn Leembruggen" <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">glenn at acousticdirections.com</A>> wrote: ><i> Hi All </I>><i> After our meeting in NY, I did some simulations using Matlab of white and </I>><i> pink MLS crest factors. When I applied a 1000 point FIR filter with 1/sqrt( </I>><i> f), to the raw MLS signal to bring it to a pink spectrum, I found that the </I>><i> crest factor 0f a ! sec MLS increased from 0 dB when unfiltered to 12.2 dB </I>><i> with pink filtering. I believe Pete Soper found similar results. I suspect </I>><i> that in this context, some of the defined benefits of the MLS signal aren’t </I>><i> as strong as we first thought. </I>><i> </I>><i> Cheers </I>><i> Glenn </I>><i> </I>><i> </I>><i> Glenn Leembruggen </I>><i> Acoustic Directions Pty Ltd </I>><i> 14 65-67 Crystal St </I>><i> Petersham 2049 Australia </I>><i> PO Box 205 Summer Hill 2130 </I>><i> tel: +61 2 9568 4684 </I>><i> fax: +61 2 9572 8939 </I>><i> mob: +61 418 207 085 </I>><i> </I>><i> The information contained in this e-document and any file attachments is </I>><i> confidential to all parties except the intended recipients. If you are not </I>><i> an intended recipient you have received this document in error and are </I>><i> prohibited from disclosing or using any of the information contained. We </I>><i> would be grateful if you would advise us of such errors immediately by </I>><i> return email. Thank you. </I>><i> </I>><i> -----Original Message----- </I>><i> From: <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">sc-04-08-bounces at standards.aes.org</A> </I>><i> [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 </I>><i> Sent: Thursday, 31 October 2013 11:26 PM </I>><i> To: Working group on Measurement and equalization of sound systems in rooms </I>><i> Subject: Re: [SC-04-08] Using pink MLS instead of conventional pink nose </I>><i> </I>><i> In message <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">DUB405-EAS265A8A255B897AA7A672F50E60F0 at phx.gbl</A>>, dated Sun, </I>><i> 27 Oct 2013, Ben Kok <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">bk-ac at live.nl</A>> writes: </I>><i> </I>>><i> so a low crest factor is preferred; in the NY meeting we considered a </I>>><i> maximum of 12 dB as being acceptable </I>><i> </I>><i> I would point out that to eliminate a source of non-repeatability, the crest </I>><i> factor should be closely controlled. But measuring higher crest factors, </I>><i> even a factor of 4, may take a relatively long time in order to ensure that </I>><i> at least one rare peak of 4 times the r.m.s. value actually occurs. For </I>><i> higher crest factors, the required observation time becomes very long </I>><i> indeed. </I>><i> </I>><i> I think that the analogue sum of four MLS signals (the same sequence but </I>><i> with different delays) has a predictable crest factor of 4, but I am not </I>><i> sure what effects the necessary low-pass filter (to get Gaussian white </I>><i> noise) and the 'pinking' filter have on the crest factor of the final </I>><i> signal. </I>><i> -- </I>><i> OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Nondum </I>><i> ex silvis sumus John Woodgate, J M Woodgate and Associates, Rayleigh, Essex </I>><i> UK _______________________________________________ </I>><i> SC-04-08 mailing list </I>><i> <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">SC-04-08 at standards.aes.org</A> </I>><i> <<A HREF="http://standards.aes.org/sc.cfm?ID=91">http://standards.aes.org/sc.cfm?ID=91</A>> </I>><i> </I>><i> _______________________________________________ </I>><i> SC-04-08 mailing list </I>><i> <A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">SC-04-08 at standards.aes.org</A> </I>><i> <<A HREF="http://standards.aes.org/sc.cfm?ID=91">http://standards.aes.org/sc.cfm?ID=91</A>> </I>><i> </I> </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000147.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000149.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#148">[ date ]</a> <a href="thread.html#148">[ thread ]</a> <a href="subject.html#148">[ subject ]</a> <a href="author.html#148">[ 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><br> Expand 000149.html 4 KB HTML - Click to view Options Copy Download Link <TITLE> [SC-04-08] Using pink MLS instead of conventional pink nose </TITLE> pre { white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ } <H1>[SC-04-08] Using pink MLS instead of conventional pink nose</H1> <B>John Woodgate</B> <A HREF="mailto:sc-04-08%40standards.aes.org?Subject=Re%3A%20%5BSC-04-08%5D%20Using%20pink%20MLS%20instead%20of%20conventional%20pink%20nose&In-Reply-To=%3CtQz2egB5RKgSFw3E%40jmwa.demon.co.uk%3E" TITLE="[SC-04-08] Using pink MLS instead of conventional pink nose">jmw at jmwa.demon.co.uk </A><BR> <I>Mon Nov 11 02:33:45 MST 2013</I> <P><UL> <LI>Previous message: <A HREF="000148.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000150.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#149">[ date ]</a> <a href="thread.html#149">[ thread ]</a> <a href="subject.html#149">[ subject ]</a> <a href="author.html#149">[ author ]</a> </LI> </UL> <HR> <!--beginarticle--> <PRE>In message <000001cedeb9$f09a4080$d1cec180$@acousticdirections.com>, dated Mon, 11 Nov 2013, Glenn Leembruggen <<A HREF="https://secure.aes.org/mailman/listinfo/sc-04-08">glenn at acousticdirections.com</A>> writes: ><i>After our meeting in NY, I did some simulations using Matlab of white </I>><i>and pink MLS crest factors. When I applied a 1000 point FIR filter </I>><i>with 1/sqrt( f), to the raw MLS signal to bring it to a pink spectrum, </I>><i>I found that the crest factor 0f a ! sec MLS increased from 0 dB when </I>><i>unfiltered to 12.2 dB with pink filtering. I believe Pete Soper found </I>><i>similar results. I suspect that in this context, some of the defined </I>><i>benefits of the MLS signal aren't as strong as we first thought. </I> I don't understand your conclusion. Your result is completely **repeatable**, which is the first priority for the test signal. The crest factor of 4.07 is quite OK if the observation time necessary to be reasonably certain of at least on 4*sigma event occurring is acceptably short. If the observation time is too short, the crest factor will be less than 4.07. The important question now is how long a practicable MLS needs to be. I suspect something between 10 s and 30 s is good. A 10 s repeat might make technicians query the nature of the signal while 30 s might be too long for an acceptable test time. Also, above 30 s, there might be long enough periods of lower or higher than average r.m.s. value to reintroduce uncertainty. Note that this is a potential problem with any sort of noise source, by no means unique to MLS sources, in fact, it may be very improbable with MLS sources. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Nondum ex silvis sumus John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK </PRE> <!--endarticle--> <HR> <P><UL> <!--threads--> <LI>Previous message: <A HREF="000148.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI>Next message: <A HREF="000150.html">[SC-04-08] Using pink MLS instead of conventional pink nose </A></li> <LI> <B>Messages sorted by:</B> <a href="date.html#149">[ date ]</a> <a href="thread.html#149">[ thread ]</a> <a href="subject.html#149">[ subject ]</a> <a href="author.html#149">[ 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><br> Expand 0 Comments Public All Members My Connections Only Me PublicAll MembersMy ConnectionsOnly Me Public All Members My Connections Only Me
