Subject Measuring Reflector Influence Date Sat Aug 3 2002 20:49 Author Tor Halmrast (tor.halmrast@statsbygg.no) File: LargeReflectorInfluence-TorHalmrast.pdf
I was asked to submit this paper where WinMLS 2000 is used for measurements and analysis. It was presented at the conference "Auditorium Acoustics: Historical and contemporary design and performance" held 19–21 July 2002 at Imperial College, London. The title is "The influence of a large reflector over the orchestra pit in an opera house". Please enjoy.

Subject Searching for feedback... Date Tue Aug 13 2002 21:39 Author Johan L. Nielsen (johan.nielsen@c2i.net)

Hi there, this is just to let you know that we are very interested in feedback from WinMLS users, so we can make the right improvements for future versions. We are especially interested in hearing about which kind of procedures you guys out there use for transducer calibration and equalization, for measurements of strength and two microphone parameters. Yours sincerely Johan L. (responsible for WinMLS room acoustics development)

Subject Norwegian national opera is using WinMLS Date Sun Sep 15 2002 11:31 Author Gunnar Ihlen (gunih@frisurf.no) File: NORWEGIAN NATIONAL OPERA USING WinMLS.doc

The Norwegian National Opera (OSLO) has recently had its auditorium analysed by Statsbygg and acoustical consultants Brekke&Strand. This has successfully led to improvements of acoustical conditions, and further aspects will be studied. Currently, same participants plus UK-based ARUP-ACOUSTICS are running major acoustical design developments, in connection with the projected OSLO NEW OPERA HOUSE. This new home of the NNO (scheduled for opening by 2008) will contain a large auditorium seating 1400, plus a small theatre of 400 seats, and a variety of different other rooms in which music-acoustics are top priority. During these processes NNO, as a client of acoustical advises, has had the opportunity of "familiarising" with the WinMLS analysing software. This has proved a very convincing tool supporting most complicated measurement- and processing tasks. The WinMLS shows to provide a number of functional options, which are easy to employ, even for the less experienced user. In the Concert- or Opera- acoustical context it is desirable to know, -and as well to be able to examine in detail-, numerous aspects of the information contained in the impulse-responses. WinMLS allows easy access to this information, with its varied display options. The fine structure of reflection patterns can be zoomed in, -as well as transforms of its frequency responses, and results are rapidly calculated, and viewed. The improved calculation capacity of strength-, as well as lateral energy parameters, which is contained in the latest version of the software (WinMLS 2000), excellently meet requirements typical of acoustical design for music performing spaces. In the same way, the options of processing correlation-based binaural parameters represent promising features, which may allow for keeping up with future advances in the arts of room acoustics. -Gunnar Ihlen

	Subject The Early Sound Field (presentation) Date Mon Sep 16 2002 23:30 Author Prof. Neil Thompson Shade (neil@akustx.com) File: SYN-AUD-CON - Acoustical Design Collaborative.ppt
Lars Morset asked me for the presentation I gave at the SynAudCon Acoustic Test and Measurement Seminar 28 – 29 August 2002. Please see the attachment. I now use WinMLS in place of my previous room acoustic measurement equipment (TEF-20 and Norsonic). It provides a very flexible, easy-to-use measurement package and a low price.

Subject Great presentation Date Tue Sep 17 2002 10:48 Author Jon Longtin (pfredrick@hotmail.com)

This is an excellent presentation. It clearly defines the many acoustical measurement parameters as well as their significance in terms of program material. The use of graphics to illustrate the various regions of the decay envelope used in the parameter definition is extremely useful. The practical suggestions and typical values for actual measurements are also very helpful. This presentation is a clear, concise collection of many important acoustical parameters and their measurements. Thanks for making it available to us.

Subject High-resolution low-frequency measurment Date Thu Nov 7 2002 10:53 Author Jon Longtin (jlongtin@ms.cc.sunysb.edu)

Is there a way to configure WinMLS (10c or the SineSweep Beta) for high-resolution (many data points) in the low-freqeuncy region (20-300 Hz or so)? I believe ETF v. 5 has a special low-frequency mode for this purpose (the MLS signal also sounds different, as it seems to be catered to low-frequencies). I am trying to acoustically treat a basement for the recording of a string bass, and the first step is to assess the detailed low-frequency response of the room using WinMLS, but I find the number of data points in the low frequency region is small, even with a long window. Also, is there a way to smooth the frequency response curves in WinMLS, e.g., by fitting a spline or curve through the points rather than straight lines. Other programs seem to do this (TEF and ETF), which makes the curves, especially in teh waterfall display more 'graceful'. Any thoughts good or bad on this? All suggestions welcome! Thanks, Jon Longtin

Subject Hi-res low freq and 'graceful' smoothing Date Fri Nov 8 2002 20:27 Author Lars Morset (morset@winmls.com) File: How to get the smoothed curves more graceful.doc

Jon, thanks for the questions. Everything in room acoustics measurements can be done with WinMLS ;-) To get an answer on how to get high frequency resolution I suggest that you have a look under the Musical Acoustics part of the forum, see http://www.nvo.com/winmls/musicalacoustics/message.nhtml?profile=musicalacoustics&UID=10004 I recommend using sine sweep over using MLS for this purpose. And if you are using the latest betaversion, then go to Measurement->Swept Sine Settings... and increase the sweep duration to11 or even 22 seconds. At the very bottom you set the length of the impulse response, this should normaly be set to less than 2 seconds, but you can change it to 4 seconds, which will give you an actual frequency resolution of 0.25 Hz About your smoothing question, please see the attached document (you will find a link to it somewhere above this text). Please let us know if you had success with this. Best regards, Lars

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Subject Measurement of Room acoustics Date Tue Jan 7 2003 21:30 Author Berthold Baumgartl (bb@soundfactory-web.de)

My configuration is. 2x Genelec 1029 (flush mounted in frontwall) + 1x Genelec 1091 Subwoofer (free standing middle of frontwall. When I measure the frequency response of 1 1029 + subwoofer I get a -+3..5dB variation in the frequency response (either left or right side). The microphone I use (Behringer ECM8000) is omnidirectional and is directed to the corrospondind box (approx.in height of the loudspeaker). If I finally turn on both or better said all 3 boxes (Subwoofer incl.) the frequency response had strong dips and is no longer in the +-3..5dB scale. I guess comb filter etc. are the reason for this. The question is now: What is the right procedure to measure a room? First lets say the left box then the right one and that's it if everything is ok with the single boxes? Or do you finally also have to measure the response of all speakers on? Would be glad to a comment on this. Berthold

Subject Room Acoustics using WinMLS Date Tue Jun 22 2004 15:25 Author Andrew Goldberg (Not available)

As this is a Genelec enquiry Lars Morset has asked me to answer this. You should measure one channel at a time otherwise you will see comb filtering. So measure the left 1029A and the 1091A then measure the right 1029A and the 1091A. The target is to get the frequency response within 5dB window. When a loudspeaker is placed in a room, the room affects the response so you will see large dips and bumps. This is the challenge of room design and why we use measurement systems to trace the problems. If you want me to look at your measurements then please send them to me (.wmb files) and I might be able to suggest something. You might also try to use a 1/4" measurement microphone rather than the one you are using.

Subject In Reply To: Measurement of Room Acousti Date Thu Feb 6 2003 23:06 Author Berthold Baumgartl (bb@soundfactory-web.de)

Thank you for the reply. I will send you the measurements in the next days when updated them. I guess with the 1/4" measurement microphone you refer to the diameter of the mic diaphragm. The outer tube diameter of the ECM800 is 12mm the open circle in the middle about 6mm. So I'm not sure what kind of diaphragm size they use, but something in between. What would you expect with a 1/4" measurement mic?

Subject Measuring the effect of diffusors panels Date Thu Feb 6 2003 23:15 Author Berthold Baumgartl (bb@soundfactory-web.de)

Is there a standard method to measure the effect of diffusor panels? What kind of signal should be used (burst tone, MLS...)? Microphone omni or cardiod pattern? Distance and incident angle of the source signal and the recorded signal? Further explanation If you read the MASTER HANDBOOK of ACOUSTIC there are a lot of diagrams showing the Time Response (Energy versus Time) of flat panels and diffusors (QRD etc..). On the diagrams you see clearly the effect of diffusion. => Direct signal => early reflections and => declining reverb part. Any suggestions on this?

Subject Mic/Speaker Placement Date Thu Jun 5 2003 08:39 Author Paul McGlashan (paul.mcglashan@xtra.co.nz)

I am evaluating WinMLS personal edition with a view to using it to measure large room acoustics used for recording instrumental ensembles e.g. string quartet. I would like to try this out but am new to this and would like to know what the best mic and speaker positioning is for capturing impulse response and measuring RT etc. Should the speaker be placed where the ensemble sits and the measurement mike placed where the mikes recording the performance would normally be -- in my case approx 1 to 2m from the front of the ensemble? What height should the measurement mike be set to -- same as the recording mikes? Also I do not have an omni-directional speaker -- can I get away with using an adequately powered single speaker e.g. Genelec 1029a? And does this Genelec have enough power and a wide enough frequency response for this? Sorry if this is basic but I can't seem to find any guidance on this aspect anywhere.

Subject Re: Mic/Speaker Placement Date Thu Jun 5 2003 11:54 Author Kjell Olav Aalmo (koaa@online.no)

If you are going to measure stage parameter the measurement mic is usually placed 1m from the source (see "stage parameter" in help file). But if you are to measure the reverberation in the studio, you can place the loudspeaker in a corner and the measurement mic in the centre of the room. In your case I also think it will be most interesting to measure the room response from where you usually have the recording mic and place the loudspeaker where the ensemble usually are. But of course you can test different positions to measure the difference in the room response to find a optimal position of the recording mic. Normally you don't need large signals to measure with WinMLS due to the measurement technique it uses. The Genelec have therefore more than enough power to do the measurement. Keep in mind that the Genelec is directive. If you need an accurate measurement of the room response it is recommended to use a omni polar loudspeaker. Sincerely Kjell Olav Aalmo

Subject Re: Mic/Speaker Placement Date Thu Jun 5 2003 23:36 Author Paul McGlashan (paul.mcglashan@xtra.co.nz)

Thanks for your help. When you say you don't need large signals due to MLS approach what SPL is typically used for large spaces? I don't have access to an omni polar speaker, however could I approximate one by say using four Genelecs each driven off a separate output of my sound card - three facing outward and one facing upward? Are there any potential phase issues with this approach? Apart from RT I am interested in measuring are EDT, C, & D. In general is the corner of the room also the best place for measuring these parameters? If I only use one speaker - how much inaccuracy will I be introducing i.e. do I really need to worry about it? Also - do you know why I do not see Clarity and Definition parameters reported in the Room Acoustics grid even though they are checked in the Room Acoustics>Parameter Settings dialogue?

Subject Re: Mic/Speaker Placement Date Mon Jun 9 2003 23:25 Author Johan L. Nielsen (johan.nielsen@c2i.net)

Hi Paul Typical SPL, don't really know numbers, the main thing is to get a good SNR so the background noise in the space enters into the equation. Omni speaker, I see you are posting from .nz. There is such a speaker at the Acoustics Research Centre at the university in Auckland. I was there when it was purchased. I think you can get pretty good RT measurements with a non-omni speaker, I would use one on its back on the floor. The other parameters you mention should be measured with an omni speaker, as they are early-field parameters. And no, don't measure with the source in a corner, unless that is where your natural source will be. These parameters will vary strongly with position. Good luck Johan L.

Subject Mic/Speaker Placement Date Tue Jun 10 2003 09:57 Author Paul McGlashan (paul.mcglashan@xtra.co.nz)

Thanks Johan - I will investigate the omni speaker at the acoustics centre -- thanks for the tip. I hadn't thought of trying a speaker on the floor. I tried three different configurations last night i.e. two speakers facing sideways (perpendicular to mic), one speaker facing forward, and one speaker in the corner - and saw some significant differences in room response. I will try the floor suggestion tonight and see how this compares with the others. Oh and I found out that C and D are only calculated when bandwidth = octave is selected. Cheers, Paul

	Subject Re: Mic/Speaker Placement Date Mon Jun 9 2003 05:46 Author Paul McGlashan (paul.mcglashan@xtra.co.nz)
About the speaker configuration - in my last post would a four speaker configuration give problems with interference?Would a better approximation to a point source be to place just two speakers back to back i.e. with the front of each speaker pointing to the sides of the room - perpendicular to the measurement mic?

	Subject WinMLS Date Tue Dec 2 2003 18:01 Author Lars Morset (morset@winmls.com)
For those that are interested in room acoustics, WinMLS participated at a room acoustics round robin at PTB, Germany and did very well. I think you will find this very interesting: http://www.ptb.de/en/org/1/14/1401/_index.htm http://www.ptb.de/en/org/1/14/1401/measurementsRRIII_public.ZIP PTB ended up purchasing WinMLS and they have been using the new beta version for more than a year.

	Subject Using NASA memory Foam as acoustic foam Date Sun Jul 12 2009 02:37 Author Wade Marsten (marsx@ca.rr.com)
Does anybody think that 4" Nasa memory foam, like the foam toppers that are egg crate shaped would work as good acoustic foam? You can get 43'sq feet x 4" that is High density 3-pound solid Visco Elastic memory foam with an egg carton shape to it for less than $125

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