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原帖由 HiViUser 于 2008-8-31 22:41 发表 
己有专业及极详細论文告诉我们， Double-Blind Trials 用在影音 AV / Audio / Video，是有大问题及不可信的！
Blind Listening Tests are Flawed
The answer is that blind listening tests fundamentally ...
老大，你自己看过没啊？你真觉得这算得上学术论文？连神秘主义都出来了，竟然被LZ奉为真理
这么颠覆性的理论怎么仅仅是个大会论文first presented at the 1991 AES convention in New York？不说在Science上发表吧，至少得在AES自己的期刊Journal of the Audio Engineering Society上发表吧？不知道这篇民科文章被其他学术论文引用过几次？[s:97]
看到这两段我都笑不动了，这是学术论文吗？
My profession gives me a unique insight into this conflict; I am a fulltime reviewer of so-called “high-end��? consumer audio products. In the course of my work, I have evaluated the sound qualities of more than 300 products and measured their technical performances. My job has been listening to, and measuring, audio equipment. My experience overwhelmingly indicates that many aspects of audio equipment quality are revealed in the listening room, not in the test laboratory. This simple thesis will be regarded by most audio professionals as a given truth unworthy of debate, yet others will denounce it as heresy and a threat to science’s role in audio engineering, and, indeed, a threat to science itself.
I cannot speak for the profession as a whole, but my listening (and that of my colleagues who write for the same publication) is anything but casual. My listening room was purpose-built from the ground up solely for music listening. Many of my colleagues are active recording engineers and use their own recordings in evaluating equipment. Some are musicians, daily exposed to the ultimate reference of live, unamplified instruments in an acoustic space. All of us became reviewers because of our lifelong dedications to music and music-reproduction technology. We take our responsibility to readers—and to audio truth—seriously; our attitude is the antithesis of caprice or whim. Indeed, the content of this paper exemplifies an approach to observational listening that is anything but cursory, casual, or superficial.
你是文科的吧？[s:97] 另外明明是Audio上的“论文”，LZ一下就引申到AV上了，厉害
Wiki也提到objectivists，subjectivists，贴上来瞅瞅，参考文献里咋没见到LZ提供的这篇雄文，可惜了啊
Audio equipment testing
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Audio equipment testing is done to provide consumers with an idea of what they are looking for and to make the process of equipment selection easier. The results are published in specialty electronics magazines, online, and in other media. Many people involved in the development or use of audio gear have an engineering background and attempt to bring a scientific perspective to evaluating audio gear. They are concerned with measurements using test equipment and would ideally like to see double-blind testing used to compare competing products. On the other hand, some reviewers believe that not all of the characteristics that produce excellence in sound reproduction are measured by the current tests. Audio reviewers in this camp also claim that double-blind testing does not provide the kind of relaxed extended-listening environment needed to evaluate an audio component. The testing methods used to evaluate equipment can be roughly divided into two groups. The two opposing factions are called objectivists, who believe that all perceivable differences in audio equipment can be measured scientifically and subjectivists, who believe that the human ear is capable of hearing details and differences which can not be directly measured.[1]
[edit] ObjectivistsObjectivists believe that audio components, accessories, and treatments must pass rigorously-conducted double-blind tests and meet specified performance requirements to meet the claims made by their adherents.
- Objectivists point out that every properly conducted and interpreted double-blind test has failed to support subjectivists' claims of significant or extremely subtle sonic differences between devices if measurements alone predict that there should be no sonic differences between the devices when listening to music.[2][3]
- Objectivists feel that some subjectivists lack engineering training, technical knowledge, and objective credentials, but nevertheless praise a product's innovation and performance. [1]
- Objectivists reject concepts that while superficially based on accepted physical principles, apply them to circumstances where they are irrelevant. The skin effect, for instance, which relates the efficiency of cables to the frequency transmitted, is often applied to audio frequencies where it is insignificant [2].
- Objectivists believe that some subjectivists' practices seem driven by fashion—e.g., the late eighties' vogue for marking the edges of CDs with a green felt marker[4] or suspending cables above the floor on small racks—and bear no relation to well-known laws of physics.
- Subjectivists often reject attempts to categorize differences in sound using measurements despite evidence of its effectiveness. It has shown that by tailoring the transfer function of a particular amplifier, it is possible to make it sound indistinguishable from another amplifier.[5]
- Measured-audio distortion is immensely higher in electromechanical components such as microphones, turntables, tonearms, phono cartridges, and loudspeakers than in purely electronic components such as preamplifiers and power amplifiers, making it logically more difficult for objectivists to accept that very subtle differences in the latter can have an appreciable effect on overall musical-reproduction quality.
British audio equipment designer Peter Baxandall, who may be considered an objectivist, has written, "I ... confidently maintain that all first-class, competently designed amplifiers, tested under completely fair and carefully-controlled conditions, including the avoidance of overloading, sound absolutely indistinguishable on normal programme material no matter how refined the listening tests, or the listeners, may be; and that when an inferior amplifier is compared with a very good one and a subjective quality difference is genuinely and reliably established, it is always possible, by straightforward scientific investigation, to find a rational explanation for this difference." Baxandall also proposed a "cancellation test", which he claimed would prove his point.[6]
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[edit] SubjectivistsOne statement that has influenced some audiophiles' values is from Harry Pearson, long-time editor of The Absolute Sound:[7]
"We believe that the sound of music, unamplified, occurring in a real space is a philosophic absolute against which we may judge the performance of devices designed to reproduce music."
- Subjectivists will rely on demonstrations and comparisons, but believe there are problems in applying double-blind methods to comparisons of audio devices. They believe that a relaxing environment and sufficient time measured in days or weeks is necessary for the discriminating ear to do its work.[8]
- Subjectivists believe that careful individual listening is an appropriate tool for discovering the true worth of a device or treatment, and will generally acquire equipment that suits their own listening or style preferences as opposed to measurable equipment performance.
Some audiophile-equipment designers and consumers are obsessed over seemingly irrelevant details. Many components, for instance, are able to reproduce frequencies higher than the limit of human hearing—20 kHz.[9] Some sources, such as FM radio, will not reproduce frequencies higher than 15 or 16 kHz.
Experienced listeners can be relied upon for valid subjective advice on how equipment sounds. British Hi-fi critic, Martin Colloms, writes that "the ability to assess sound quality is not a gift, nor is it the feature of a hyperactive imagination; it is simply a learned skill", which can be acquired by example, education and practice[10]. In any event, the eventual purchase decision will be made by the end-user, whose "perception is reality" and can be influenced by factors other than the equipment's actual performance.
[edit] Opposing viewpointsMain article: Tube sound
Objectivists attack Vacuum-tube amplifiers as vastly inferior because, in addition to their substantially higher total harmonic distortion, they require rebiasing, are less reliable, generate more heat, are less powerful, and are usually more expensive. [3]Subjectivist believe that while tubed electronics are less linear than solid-state electronics at high-signal levels, they are much more linear at low-signal levels — less than one watt. Most musical signals spend most of the time at these low levels.
Main article: Analog sound vs. digital sound
Objectivists claim that digital sound is superior to analog sound because it has no clicks, pops, wow, flutter, audio feedback, or rumble, has a higher signal-to-noise ratio, has a wider dynamic range, has less total harmonic distortion, and has a flatter and more extended frequency response. [4] [5] Subjectivists however claim that the process of converting a bit-stream to an analog waveform requires heavy filtering to remove spurious high-frequency information and that it should be expected that such filtering should involve some signal degradation and a large amount of phase shift in the passband. They point out that commonly-used consumer-grade digital-to-analog converters (DACs) exhibit very poor linearity at low levels. Both problems, at first dismissed, were then addressed by such solutions as digital filtering, oversampling, and the use of DACs operating at 20-bit (or higher) resolution. The introduction of the new higher-bandwidth high-resolution music formats is a tacit admission of the reality of this issue. Musician Neil Young, for example, is a harsh critic of the sound of the original CD format but has approved of the sound of the newer SACD format with its greater safety margin between its ideal behavior and the requirements set by the limits of human hearing.
Objectivists consider total harmonic distortion to be an accurate measure of sound quality. Subjectivist however claim that total harmonic distortion has been proven by scientific testing to correlate poorly with perceived sound quality. The type of distortion is more significant. For instance, distortion by even harmonics has been shown to be less objectionable than distortion by odd harmonics.
Subjectivists believe that sound quality is degraded by large levels of negative feedback in amplifiers. Objectivists claim that negative feedback is beneficial to amplifier stability and produced good test results using steady-state waveforms. Subjectivists however believe that the application of negative feedback is inherently problematic for constantly-changing waveforms such as those that occur in music.
Subjectivists claim that there is a limit to what can be tested using Objective measurements. High-end audio companies which do rely on quantitative evaluations guard their measurement techniques as trade secrets. These are far more complex than the techniques which are in the public domain e.g. total harmonic distortion, transient intermodulation distortion. Subjectivist point out that objectivists since the 1970s no longer tout distortion measurements in their advertisements as there is a general consensus that an amplifier with 0.01% total harmonic distortion may not sound "better" than one with 0.1% total harmonic distortion - especially if the lower distortion is achieved with (excessive) feedback.
Overall, the subjectivists' world is looked upon by objectivists as being a hotbed of gullibility and fraud, its marketing engine driven primarily by either a constant desire for one-upmanship or a more benign desire to tinker with equipment. In particular, the tinkering drive is fed by wild claims for minor parts of the system such as cables. Objectivists, however, are often harshly dismissed by subjectivists as meter men — people who simply refuse to recognize what the subjectivists consider obvious. The debate is rather heated in certain quarters, and even James Randi chimed in on the issue. [6]
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[edit] Difficulty of testingIt is difficult, but very important, to match sound levels before comparing systems, as minute increases in loudness—more than 0.15 dB[11] or 0.1 dB[12]—have been demonstrated to cause perceived improvements in sound quality.
Listening tests are subjected to many variables, and results are notoriously unreliable. Thomas Edison, for example, showed that large audiences responded favorably when presented both live performances by artists and reproductions by his recording system,[13] which today would be regarded as primitive in quality.
Similarly, results of component evaluation between various listeners or even the same listener under different circumstances cannot be easily replicated or standardized.
Similarly, the acoustic behavior of the listening room—the interaction between loudspeakers and the room's acoustics—and the interaction between an electromechanical device (loudspeaker) and an electronic device (amplifier) are subjected to many more variables than between electronic components. Thus the "difference" in sound quality between amplifiers is actually the ability of an amplifier to interface well with loudspeakers or a lucky combination of loudspeaker, amplifier, and room that works well together[14].
The introduction of switching apparatus, with either metal connection (mechanical switches) or electronic processing (solid-state switches), may, some believe, obscure the differences between the two signal sources being tested.
References
^ "Basic Issues of Equipment Reviewing and Critical Listening: Our Present Stance," Peter Aczel, The Audio Critic, issue number 16, page 31 (PDF page 25), accessed 2007-05-18. ^ "The Ongoing Debate about Amplifier "Sound"", Ian G. Masters (September 1, 2002).
^ Paste This in Your Hat! - What Every Audiophile Should Know and Never Forget, Peter Aczel, Biline.ca, Accessed 2007-05-11 ^ "Bewaring of the Green". Snopes.com (May 15 - June 15, 1990). ^ Interview with Sunfire's Bob Carver Gordon Brockhouse, Audio Ideas Guide, Accessed 2007-05-11 ^ Baxandall, Peter J. Audible amplifier distortion is not a mystery. Wireless World, November 1977, pp. 63. ^ "The Absolute Sound". Retrieved on 2007-01-23. ^ The Objective Subjective Review Debate, Martin Colloms, 1991, Retrieved on 2007-05-09 from hificritic.com ^ "Hearing Loss", Timothy C. Hain, MD. (February 26, 2006).
^ Working in the Front Line:An approach to equipment reviewing, Martin Colloms, Stereophile, Vol.14 No.1, January 1991 Retrieved on 2007-05-09 from hificritic.com ^ "Our Last Hip Boots Column," Peter Aczel, The Audio Critic, issue number 29, Summer/Fall 2003, page 5 (PDF page 6), accessed 2007-07-05. ^ "The Amp/Speaker Interface: Are Your Loudspeakers Turning Your Amplifier into a Tone Control?" E. Brad Meyer, Stereo Review, June 1991, page 54, accessed 2007-07-05. ^ "The History of the Edison Disc Phonograph". About.com. - ^ The Amp/Speaker interface, Brad Meyer, Sound & Vision Magazine, Accessed 2007-05-11
[ 本帖最后由 AMG 于 2008-9-1 00:43 编辑 ] |
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