| How can a listening test be objective? How can we separate "different" from "better"?This is a very tough question to answer. For example, regarding listening tests for jitter, no one that I know has reached the point of being able to say: "100 picoseconds of white noise jitter mixed with 25 picoseconds of signal-correlated jitter sounds better than 100 picoseconds of signal-correlated jitter mixed with 25 picoseconds of white noise jitter".No, we have not reached the degree of sophistication where we can judge "better" in that fashion.However, a number of experienced listeners have been able to use the judgemental term "better" in ways that correlate quite well with the measurable physical phenomena that are under investigation.For example:First: one definition of "better" is the source which sounds closer to the analog master tape, or the live source if it is available.Second: Those of us who have been chasing the jitter phenomenon have begun to educate our ears and recognize the sonic differences that different types and degrees of jitter cause. Please note that in every case I use the same D/A converter to monitor the different sources under test at repeatable monitoring gains.If you wish to begin entering down this jittery road, I suggest you start listening to the easiest form of jitter to recognize, one which every user of Workstations can hear every day, while monitoring through a high-resolution playback system. (A high-resolution playback system consists of a good 24-bit D/A converter, wide range monitors in an acoustically treated room, power amplifier with wide dynamic range, and a quiet listening environment).The easiest form of jitter to recognize is signal-correlated jitter. Signal-correlated jitter adds a high-frequency (intermodulation) edge to musical sounds when monitored on a susceptible D/A Converter. Obviously, a theoretically perfect D/A would not be susceptible to jitter. We must not blame the message directly...just that the message is contaminated with jitter.Every day I load into the workstation connectors while listening through the desk, I hear (and am bothered by) the most primitive form of proof that correlated jitter is audible: The sound is different during the load-in than during the immediate playback from the hard disk! It also sounds demonstrably worse during the load in than during the playback.This is attributable to the intermodulation of Sonic's master clock by signal-correlated jitter during the loadin. During playback, since the source is no longer feeding digital audio, even though the DAW is still locked to the external clock, the external clock is much more stable from the DAW's point of view. Its PLL is no longer modulated by the digital audio that is combined with the external clock. This well-known phenomenon, known as signal-correlated jitter, has been documented by researcher Malcolm Hawksford. See AES preprint titled "Is the AES/EBU S/PDIF Interface Flawed" AES Journal 1995. This form of jitter is quite audible.After an engineer learns to identify the sound of signal-correlated jitter, then you can move on to recognizing the more subtle forms of jitter and finally, can be more prepared to subjectively judge whether one source sounds better than another.Here are some audible symptoms of jitter that allow us to determine that one source sounds "better" than another with a reasonable degree of scientific backing:It is well known that jitter degrades stereo image, separation, depth, ambience, dynamic range.Therefore, when during a listening comparison, comparing source A versus source B (and both have already been proved to be identical bitwise):The source which exhibits greater stereo ambience and depth is the "better" one.The source which exhibits more apparent dynamic range is the "better" one.The source which is less edgy on the high end (most obvious sonic signature of signal correlated jitter) is the "better" one.Does this help you?Seems like this could be very subjective. I could almost certainly agree on 'sounds different.' To be fair, I have not been involved in the kind of research you have done in this area but I still feel there is a lot of subjectivity involved.I recently attended the NAB convention and watched some demos of video line doublers and quadruplers. While in some ways they 'improved' the projected image, I could not flatly say that they made every aspect of the picture 'better.' It was decidedly 'different' but among the group I was with we couldn't all agree on what aspects we liked and didn't like about the 'improved' picture.That's for sure. Well, line doublers actually alter the data which is sent to the monitor, so, unlike with audio jitter reduction units, the data is changed, and you get into very valid subjective questions. The question of "better" is definitely a slippery subject. I don't pretend to have all the answers, but to me, the audio copy which sounds most like the original points the direction of the degradation. Then, I can relate an experience with two different jitter reduction units, both of which produced excellent-sounding outputs, but both sound very different from one another. One has a slightly "flabby" bass, the other a tighter bass. At least both of them sound "better" than the jittery copy as monitored without the jitter reduction. So, when comparing two different D/A converters or two different jitter reduction units, even more subjective judgment enters into the picture. I agree with Steve Potter that "Better" is a very complex subject! Here's a followup on the maillist from Peter Cook of the CBC:Date: Wed, 1 May 1996From: pcook[a]toronto.cbc.ca (Peter G. Cook)Subject: Re: DEFINITIONS OF "better" versus "worse" soundA fine mini essay Bob. Perhaps you could add this on your web pages.At 08:21 1/5/96, Bob Katz wrote:Therefore, when during a listening comparison, comparing source A versus source B (and both have already been proved to be identical bitwise):The source which exihibits greater stereo ambience and depth is the better one.The source which exhibits more apparent dynamic range is the better one.The source which is less edgy on the high end (most obvious sonic signature of signal correlated jitter) is the better one.The better one, and it is better, is also easier to listen to. . . less fatiguing. I would also add to this that the low end just "feels" bigger and more solid. This is perhaps a psychoacoustic affect more than a measurable one. It may be that the combination of a less edgy high end and greater depth and width makes the bass seem better.All of this makes sense if thought of in terms of timing (that is what we're talking about isn't it ;-]). With minimal jitter nothing is smeared, a note and all its harmonics line up, the sound is more liquid (a term probably from the "audiophile" crowd but one which accurately describes the sound none the less), and images within the soundstage are clearly defined.-Peter | | 如何能聆听测验是客观的？我们怎样才能单独的“不同”的“更好” ？
这是一个非常艰难的问题的答案。例如，关于听力测试，抖动，没有人，我知道已经到了点能够说： “ 100皮秒的白噪声与抖动25皮秒混合信号相关抖动的声音比100皮秒的信号相关抖动混合25皮秒的抖动白噪声“ 。
不，我们还没有达到成熟的程度，我们可以判断“更好”这种方式。
但是，一些有经验的听众已经能够判断长期使用“更好”的方式，相关性很好的可衡量的物理现象，正在调查中。
例如：
第一：一个定义， “更好”的来源是这听起来更接近模拟母带，或生活来源如果可用。
第二：我们这些谁一直追逐的抖动的现象已经开始教育我们的耳朵和承认声波差异，不同类型和不同程度的抖动事业。请注意，在每一种情况下我用的是相同的D / A转换器，以监测不同来源下测试可重复监测成果。
如果你想开始进入了这个紧张的道路，我建议你开始听的最简单形式的抖动承认，其中每个用户的工作站可以听到每一天，同时监测，通过高分辨率播放系统。 （高分辨率播放系统包括一个良好的24位D / A转换器，广泛的听觉监测治疗室，功率放大器与宽动态范围，和一个安静的聆听环境） 。
最简单的形式的抖动承认是信号相关抖动。信号相关抖动增加了一个高频率（互）边缘音乐声音时监测易感D / A转换器。显然，从理论上完善的数/模不会容易抖动。我们绝不能责怪讯息直接...只是信息污染的抖动。
每天我都会载入到工作站连接聆听通过服务台，我听到（和我所困扰）最原始形式的证明，相关抖动的声音：声音是不同的负载中比直接播放从硬盘！它还声音明显恶化期间负荷比在播放。
这是因为互调的Sonic的主时钟信号相关抖动在loadin 。在播放过程中，由于源不再喂养数字音频，即使地位仍然被锁住的外部时钟，外部时钟稳定得多的地位的观点。其频率已不再是调制的数字音频这是结合外部时钟。这一众所周知的现象，称为信号的相关性抖动，已经记录在案研究员马尔科姆Hawksford 。见AES公司预题为“是AES公司/欧洲广播联盟的S / PDIF接口缺陷”杂志1995年AES公司。这种形式的抖动很声响。
经过工程师学会识别声音信号的相关性抖动，然后你可以移动到认识到更微妙形式的抖动和最后，可以更准备主观判断一个来源优于另一种声音。
以下是一些声响症状的抖动，使我们能够确定一个来源的声音“更好”比其他的合理程度的科学支持：
众所周知，抖动降低立体图像，分离，深入，氛围，动态范围。
因此，当在听比较，比较来源阿与源乙（都已经被证明是相同位） ：
这些展品的来源更大的立体氛围和深度是“更好”的。
这些展品的来源更为明显的动态范围是“更好”的。
消息来源是不太毛躁高端（最明显的声波信号签署相关抖动）是“更好”的一个。
这是否能帮你吗？
看起来这可能是非常主观的。我几乎可以肯定同意'的声音不同。公平地说，我没有参与这种研究你做了这方面的，但我仍然感到有很大的主观性参与。
我最近参加了国民会议及看了一些演示视频线路倍增器和quadruplers 。虽然在某些方面，他们'改善'预计形象，我不能断然说，他们取得的每一个方面的图片'更好。这是决定性的'不同' ，但把这一群体中，我与我们不可能都同意哪些方面我们喜欢和不喜欢的'改进'图片。
这是肯定的。嗯，实际上改变线路倍增器的数据发送到监控，因此，与有声抖动减少单位，数据的改变，你进入非常有效的主观问题。的问题， “更好”绝对是一个防滑的问题。我也不敢自诩拥有所有的答案，但对我来说，音频复制这听起来像最原始点的方向退化。然后，我的经验可以涉及两种不同的抖动减少单位，这两个生产优良冠冕堂皇的产出，而且声音非常不同彼此。其中有一个稍微“软弱”的低音，其他更严厉的低音。至少有两个人声音“更好”的紧张比副本监测没有抖动减少。因此，当比较两个不同的D / A转换器或两个不同的抖动减少单位，更主观判断进入图片。我同意史蒂夫波特说， “更好”是一个非常复杂的问题！这里有一个后续的邮件列表由彼得库克的央行：
日期： Wed ， 96年5月1日
来自： pcook [ 1 ] toronto.cbc.ca （彼得G库克）
主旨： Re ：对“更好地”与“坏”的声音
罚款小作文鲍勃。也许你可以购买这个在您的网页上。
在08:21 1/5/96 ，鲍勃卡茨写道：
因此，当在听比较，比较来源阿与源乙（都已经被证明是相同位） ：
这exihibits的来源更大的立体氛围和深度是更好的。
来源更明显的物证动态范围是更好的一个。
消息来源是不太毛躁高端（最明显的声波信号签署相关抖动）是更好的。
更好的，这是更好的，也比较容易听。 。 。不到fatiguing 。我还要补充说，低端只是“感觉”更大，更坚实。这也许是心理影响超过衡量一个。这也许是因为相结合的较前卫的高端和更大的深度和广度使低音似乎更好。
所有这一切才有意义，如果思想在时间（这是我们谈论的是不是;-]).以最少的抖动没有污蔑，说明其所有谐波行了，声音更液体（任期可能从“古典音乐”人群，但它准确地描述了良好的无以较低者为准） ，和图像的声音显然是界定。
彼得
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