ABX software for Unix (source code) can be found at� abx.c from the Lame Source

ABX software for Linux can be found at� http://www.beryllium.net/~remco/linabx/

ABX software for Macintosh can be downloaded here: program/MacABX.hqx . This software was provided courtesy of Chris Johnson who has an audio-related web site at http://www.airwindows.com .

An ABC/Hr comparator can be found at Darryl Miyaguchi's web site at http://ff123.net/abchr/abchr.html

Another ABX Comparator can be found at Timo Esser's web site at http://www.esser.u-net.com/abx.htm

The WINABX comparator can be downloaded from� http://www.kikeg.arrakis.es/winabx/winabx.zip . Sound card related test files can be downloaded from http://www.kikeg.arrakis.es .

The foobar2000 music player includes a ABX comparator that can be downloaded from http://www.foobar2000.org/components.html#foo_abx .

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PCABX IS NOT intended to be a general replacement for properly-designed listening tests involving audio equipment that is already in your listening room. There are many situations where PCABX is beneficial, even when the equipment is directly available to you for listening.�

Properly-designed listening tests have been behind the development of important technological advances such as perceptual coders (MP3) and various audio� products, particularly loudspeakers.�

Unfortunately, over the past 20� years, very few (prior to PCABX, perhaps 1,000 people) have had the opportunity to participate in a properly-designed listening test. Most properly-designed listening tests have taken place in research and development facilities belonging to universities and large corporations.�

PCABX provides the average recording engineer or audiophile the opportunity, in his own listening room, to apply the power of properly-designed listening tests to his personal development as a sensitive, reliable listener. Thus, properly-designed listening tests can benefit a far larger group of people and inform their purchase decisions.

If you are already familiar with PCABX, Click here to proceed directly to the PCABX Listening Room.�

If you already know about PCABX and want to get started right away, please click here.

This web site encourages conformance with applicable international technical standards organizations publications including� ITU Recommendation BS 1116-1. You can find out more about this document at http://www.itu.int/itudoc/itu-r/rec/bs/1116-1.html . The approximate cost of this 26 page document in MS Word or PDF format is $12.00 US as of 10/1/2000.�

This document says in part:

--- begin quotes from ITU BS 1116-1 ---

"The ITU Radiocommunication Assembly, considering

a)������������� that Recommendations ITU-R BT.500, ITU-R BS.562, ITU-R BT.710 and ITU-R BT.811 have established some methods for assessing subjective quality of audio and video systems;

b)������������� that subjective listening tests permit assessment of the degree of annoyance caused to the listener by any impairment of the wanted signal during its transmission between the originating source and the listener;

c)������������� that classical objective methods may not be adequate in assessing advanced audio coding schemes and that perceptual objective assessment methods are being developed for testing the sound quality of sound systems;

d)������������� that the use of standardized methods is important for the exchange, compatibility and correct evaluation of the test data;

e)������������� that the introduction of new advanced digital audio systems exploiting psycho-acoustic properties, especially with small impairments requires advancements in subjective assessment methods;

f)�������������� that the introduction of new multichannel stereophonic sound systems with or without accompanying picture requires new subjective assessment methods, including the experimental conditions,

recommends

...

Annex 1

...

Test Method:

To conduct subjective assessments in the case of systems generating small impairments, it is necessary to select an appropriate method. The �double-blind triple-stimulus with hidden reference� method has been found to be especially sensitive, stable and to permit accurate detection of small impairments. Therefore, it should be used for this kind of test.

...

--- end quotes from ITU BS 1116-1 ---

PCABX is generally considered to be a �double-blind triple-stimulus with hidden reference� method or an acceptable equivalent.��

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Ten (10) Requirements For Sensitive and Reliable Listening Tests

(1) Program material must include critical passages that enable audible differences to be most easily heard.

(2) Listeners must be sensitized to a audible differences, so that if an� audible difference is generated by the equipment, the listener will notice it and have a useful reaction to it.

(3) Listeners must be trained to listen systematically so that audible problems are heard.�

(4) Procedures should be "open" to detecting problems that aren't necessarily technically well-understood or even expected, at this time. A classic problem with measurements and some listening tests is that each one focuses on one or only a few problems, allowing others to escape notice.�

(5) We must have confidence that the Unit Under� Test (UUT) is representative of the kind of equipment it represents. In other words� the UUT must not be broken, it must not be appreciably modified in some secret way, and must not be the wrong make or model,� among other things.

(6) A suitable listening environment must be provided. It can't be too dull, too bright, too noisy, too reverberant, or too harsh.�� The speakers and other components have to be sufficiently free from distortion, the room must be noise-free, etc..

(7) Listeners need to be in a good mood for listening, in good physical condition (no blocked-up ears!), and be well-trained for hearing deficiencies in the reproduced sound.

(8) Sample volume levels need to be matched to each other or else the listeners will perceive differences that are simply due to volume differences.

(9) Non-audible influences need to be controlled so that the listener reaches his conclusions due to "Just listening".�

(10) Listeners should control as many of the aspects of the listening test as possible. Self-controlled tests usually facilitate this. Most importantly, they should be able to switch among the alternatives at times of their choosing. The switchover should be as instantaneous and non-disruptive as possible.

http://www.silcom.com/~aludwig/Sound_demos.html

"Arny Kruger has posted free downloadable software for performing ABX tests to compare two .wav files. His site also includes a selection of sample files to illustrate the effect of filtering out high frequencies, truncating bits, etc. Listen with good quality headphones (I use Sennheiser HD-545's). Otherwise effects will be washed out by the quality of computer speakers and the room you are sitting in. Standard computer sound cards are not the ultimate in fidelity, but they are adequate. One way to make A-B comparisons of multiple sound files is to open multiple Media Player windows, one for each file, and then play the files quickly in sequence. But Arny's ABX tester is better."

http://www.3dsoundsurge.com/features/weeks/Week29May.html :

"Can you hear the difference between 24 and 16 bits?
If you don't have a high quality professional soundcard that question may be tough to find an answer to but you Kr�ger's PCABX.com site will also let you see if you can hear the difference between 16, 15, 14, 13, 12, 11 and 10 bits."

http://www.3dsound.com/archive/week127.html :

"You can do you own listening tests and find some more info over at www.pcabx.com."

http://www.commvergemag.com/commverge/extras/P178673.asp :

"Arny Krueger's PCABX site contains detailed before-and-after oscilloscope displays showing the audio alterations caused by various codecs, as well as a number of test tone files."

http://commverge.e-insite.net/commverge/issues/2000/200012/12dd3.asp

"Arny Krueger, who maintains of the PC ABX audio testing Web site (www.pcabx.com), wrote to recommend a better approach. "I find it is helpful to use complex multitones for testing, because they tend to load up the codec with multiple concurrent frequencies, just like real-world program material," he said. "Pink or white noise is generally no stress at all for most good coders, because a fully loaded coder will reduce the signal-to-noise ratio in the frequency bands, producing noise with about the same power-spectral density as the original, but not actually the original noise."

http://fastforward.iwarp.com/setup.html :

"I use Arny Krueger's PC ABX program to conduct the equivalent of double-blind listening tests."

http://oeonline.com/~djcarlst/abx_hdwr.htm:�

"PCABX Comparator New in 1999"

http://www.sospubs.co.uk/sos/nov00/articles/pcnotes.htm

"Although the test files are nearly all in 16-bit/44.1kHz format, and quite a few are therefore about one megabyte each to download, the ABX Comparator is still an excellent way to help train your ears to hear problems in the mix. Best of all, it's freeware. Well done Arny! (www.pcabx.com/getting_started.htm)."

http://musepack.org/faq/

"I think I heard a problem with MPC encodings. What do I do now?"

"A: First: - Test the clip with an ABX (such as pcabx, found at (www.pcabx.com) tester using double blind tests. Often there's no problem, you can only hear the problem as long as you know what you are hearing. In other words, the placebo effect makes you *think* that you can tell a difference, but you actually cannot. Then the difference is only pure imagination. If you find that, after blind testing using ABX software, you can truly tell the difference between the source file and the encoded file..."

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(If your web site mentions PCABX, I'll strongly consider posting a link here. Send me email by clicking this link: Arny Krueger.)

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Please see: http://www.music.miami.edu/programs/mue/Research/sbrowne/thesis.pdf ,
page 63 (The 70th page of the .PDF file).

"The testing mechanism used was the PCABX testing software."