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Audibility of 20kHz brick wall filtering, samples provided for ABXing - 24/96 sound card required
post Jan 8 2009, 17:30
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This test continues the discussion in this thread...


...using the impulses provided at the end of that thread as filters.

I've filtered some 24/96 audio with the linear phase (050) and maximum phase (100) 20k impulses, and uploaded the results here:


The "reference" is just the original convolved with an impulse, i.e. a null operation.

All files are 24-bit 96kHz sampled .wav files. You will need a 24/96 sound card to listen to these files, and use something like foobar2k which plays the files properly.

The "reference" should sound best, the "maximum phase" file should sound worst. Can anyone ABX a difference?

(I don't claim to be able to hear any difference).

btw, the files are time aligned to the nearest sample, though the maximum phase filter introduces a sub-sample delay and slight phase shift. I've confirmed that all low pass filters have identical amplitude responses, and that the pass band of the low pass filters matches the level of the unit impulse. Source: Cool Edit Pro frequency analysis, 65536 FFT, Linear View, Range 24 dB, Reference -90 dBFS, window expanded to fill my screen, absolutely no different between plots.

In the last second end of each audio file is a unit impulse, filtered - hence the filter itself is "included" in the file, for easy checking, analysis and verification.

(I used Cool Edit Pro to do the convolution (filtering). I'm not entirely convinced by its algorithm - there are some errors 100dB below the signal, verified by convolving with a single impulse. From the nature of the errors, I assume it's performing time domain convolution by frequency domain multiplication, which is quite common, and there are some rounding errors which would be lost in the noise of a 16-bit signal, but are apparent with the 24-bit signal)


P.S. When I tried to FLAC encode these files (using FLAC 1.2.1b in Windows XP), the FLAC verifier from the same package (not the one called automatically when encoding, but the stand-alone one) reported errors, hence I've provided .wavs instead. I hope my system isn't on the way out - can anyone else reproduce this problem?
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post Jul 7 2010, 12:58
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ReplayGain developer

Group: Developer
Posts: 5403
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The files I linked to in this thread have expired.

I've re-uploaded them here:

www.media fire.com/?sharekey=605ee2b5f85656f5e62ea590dc5e5dbb4b15895e9b73e977e91dc00c2f906379

You'll need to copy+paste the URL, and remove the space between media and fire, to make it work.

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Posts in this topic
- 2Bdecided   Audibility of 20kHz brick wall filtering   Jan 8 2009, 17:30
- - 2Bdecided   btw, the maximum phase file should sound worst. I...   Jan 9 2009, 12:51
- - 2Bdecided   I guess this is quite a challenge then? Cheers, ...   Jan 13 2009, 16:38
|- - 2Bdecided   I've attached some spectral plots to show how ...   Jan 15 2009, 21:45
- - Axon   I, probably like most people here, can't hear ...   Jan 15 2009, 22:20
|- - 2Bdecided   QUOTE (Axon @ Jan 15 2009, 21:20) I, prob...   Jan 16 2009, 12:15
- - MLXXX   David, I tried the reference against the maximum p...   Jan 27 2009, 11:43
- - 2Bdecided   Thank you MLXXX. It's great to see someone tak...   Jan 27 2009, 13:25
- - MLXXX   Hopefully some others can do an ABX and report the...   Jan 27 2009, 14:25
- - 2Bdecided   The files I linked to in this thread have expired....   Jul 7 2010, 12:58
|- - Kees de Visser   QUOTE (2Bdecided @ Jul 7 2010, 13:58) The...   Jul 9 2010, 19:02
- - Cavaille   Ugh, I donīt like ABX... always stressing. Took me...   Jul 10 2010, 02:41
- - 2Bdecided   That's two independent positive ABX results - ...   Jul 10 2010, 10:27
- - mzil   Unless it is on my end, the rapidshare download pa...   Nov 12 2014, 22:45
|- - Kees de Visser   QUOTE (mzil @ Nov 12 2014, 22:45) Unless ...   Nov 12 2014, 23:14
- - 2Bdecided   Another ABX report of these samples can be found h...   Nov 13 2014, 18:25
- - bandpass   As discussed in another thread it seems that foo_a...   Nov 14 2014, 07:05
|- - Arnold B. Krueger   QUOTE (bandpass @ Nov 14 2014, 02:05) As ...   Nov 14 2014, 10:40
- - xnor   Yeah please post this here in a more detailed fash...   Nov 14 2014, 13:10
|- - bandpass   QUOTE (xnor @ Nov 14 2014, 13:10) Yeah pl...   Nov 14 2014, 14:24
- - Wombat   foo_abx 2.0 beta 4 report foobar2000 v1.3.4 2014-1...   Nov 14 2014, 16:25

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