HOLMImpulse: Measuring Frequency- & Impulse-Response
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 9th June 2009, 06:44 PM #101 askbojesen   diyAudio Member   Join Date: Mar 2003 Location: Denmark, Copenhagen A little more formulas If: A[f] = 1/H[f]; C[f] = Conj(H[f])/(Conj(H[f])H[f]+ε[f]) then C[f]=A[f]*B[f], where B[f] is the bandpass function B[f] = 1/(1+ε[f]/|H[f]H[f]|) Note that H[f] != 0 for the logsweep (Also for the 32 bit float or 64 bit double)
 9th June 2009, 07:16 PM #102 gedlee   diyAudio Member     Join Date: Dec 2004 Location: Novi, Michigan The impulse response data is written out in a form that makes it difficult to read back into another program. This is because it is in two different formats, integer and float on a single line. The integer values of the data are pretty much useless since they just increment by one from one line to the next, so why print them? Just put the starting value and the length in the header and let it go at that. Then just print one float value per line and any program could read in this data. __________________ Earl Geddes Gedlee Website
KSTR
diyAudio Member

Join Date: Jul 2007
Location: Central Berlin, Germany
Re: Regulized IFFT - bandpassed IFFT

Quote:
Seconded! And I really should read up on signal theory, I see!

Quote:
 Without µ[f] we would simply have: C[f] = 1/H[f] Applying µ[f] is nothing else than a bandpass of the resulting response. Like when Klaus is sweeping from 1000 Hz, then he knows that the response below 1000 Hz is not valid.
That bandpass functionality is already there, for the result, in the options dialog, right?

Quote:
 I'm in doubt if I should adopt this bandpass for the log-sweep - If I did Klaus and Earl would require that it could be disabled, so they could get the raw impulse
From the practical standpoint this might nevertheless be a good idea, HF-limiting the stimulus (LF we have already). Like when I use high sample rates (96k++) to lessen the burden for both the DUT(+amplifier) and the imperfect ADC/DAC-chain, measuring DUTs with higher distortion ... but I better leave that decision to others/you, I think.

- Klaus

 9th June 2009, 08:30 PM #104 askbojesen   diyAudio Member   Join Date: Mar 2003 Location: Denmark, Copenhagen HOLMImpulse new release 1.1.5.0 Version 1.1.5.0 (2009-06-09) http://www.holmacoustics.com/holmimpulse.php Changelog http://www.holmacoustics.com/downloa.../ChangeLog.txt Features/Changes: * File type *.hlm registered for HOLMImpulse (Double-click on file.hlm) * Impulse-Graph improved graphics (Peak-To-Peak) * Export impulse response: Sample number is optional (CheckBox) * Max signal Length = 20 (Was 21, but crashed need to troubleshoot) * New Icons Bugfixes: * Post-Time window to small (Increased by x10) * Impulse-Graph x-axis-label postition * Harmonic distortion: Only plotting at frequencies where data is available Issues http://www.holmacoustics.com/downloa...lse/Issues.txt
 10th June 2009, 12:30 AM #105 KSTR   diyAudio Member     Join Date: Jul 2007 Location: Central Berlin, Germany ^^^Now that was quick! Thanks!
JohnPM
diyAudio Member

Join Date: Oct 2008
Re: Regulized IFFT - bandpassed IFFT

Quote:
 Originally posted by askbojesen I'm in doubt if I should adopt this bandpass for the log-sweep - If I did Klaus and Earl would require that it could be disabled, so they could get the raw impulse
If you don't do this (or something similar ) on a band-limited sweep then noise gets boosted where the stimulus energy is low and the quality of the impulse response can be severely degraded, it doesn't take a lot of LF noise to greatly change the appearance of the IR.

diyAudio Member

Join Date: Mar 2003
Location: Denmark, Copenhagen
How about a HOLM for Dummies

Quote:
 Originally posted by doug20 How about a HOLM for Dummies? (Me, I feel dummer by the day on this site!!). I do not want to bog down this thread with really silly and probably easy to answer questions, could we create a HOLM for dummies thread?
Well now, I believe you are right, so I have started a new thread:

HOLMImpulse: Measurements in practice

Now we will see if this new thread gets a life...

 10th June 2009, 11:02 PM #108 askbojesen   diyAudio Member   Join Date: Mar 2003 Location: Denmark, Copenhagen Correction to above... HOLMImpulse: Measurements in practice HOLMImpulse: Measurements in practice http://www.diyaudio.com/forums/showt...hreadid=145662 sorry
 13th June 2009, 02:31 PM #109 David_Web   diyAudio Member   Join Date: Sep 2008 Thought this fitted better here instead of the other thread. Any way to disable auto detection? The reflected sound when doing measurements close up will not affect things that much, and it is very annoying to disable it after every measurement. If you measure at 80dB at 30cm and the closest reflection is at 1m. The reflected sound will be -16.5dB down. That will add 0.1dB to the total sound. Well I'm not that good at sound theory so it might be wrong but still. When you want to see a trend in response ungated is needed. Hmm. Any way to use a rollof for gating? Remove the HF part of the reflection and then leave the LF part to not mess up the shape of the response. A little checkbox would be nice. I looked at everything but I could not find one. Sorry if I missed it. Any news on IR export to wave?
 13th June 2009, 07:56 PM #110 KSTR   diyAudio Member     Join Date: Jul 2007 Location: Central Berlin, Germany Suggestion for an additional display feature (say, for version 2.xxx), Arsinh scaling: A novel mapping with natural transition from linear to logarithmic scaling - Klaus

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