主题：[讨论]延时特性 - 这段文字怎样理解呀？

看不懂， 谁能翻译这段文字？




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大概意思是说：
由于分频网络的多样性、驱动单元本身特定的时域响应尤其是单元的相关性，导致扬声器系统带宽内的整体时域性能倾向于不一致（不恒定）。图5-26的由Blauert和Laws提供的判断准则说明，按照普遍的可闻度而言的话，理想的群延时响应不是绝对必要的。为获得这个数据，Blauert 和 Laws将群延时变化范围小心地调整到一个倍频程中心内，得到了如曲线A这样的可闻阈。
一般而言当今的扬声器系统的群延时都不会超过这个包络，因而在与一个没有群延时异常的系统对比时也不会被察觉。

图5-26 是Blauert和Laws根据实验结果画出的电声系统中的群延时可闻的判断准则。

使用长的中频号角的扬声器在这里（指针对其群延时特性而言）作为“接近犯罪的人”（指引起群延时的问题），除非已经使用延时补偿（通常通过数字处理）。老式的全频号角系统有很长的低频号角，同样是潜在的“罪犯”，除非已经获得类似的测量（来证明或者用于补偿）。

多谢了。

XP 老大果然不同反响。
所以说，只有使用中频号角（而不加补偿）的扬声器系统，才可能出现群延时的可闻性问题？

应该是的
短号筒由于延时问题不明显（此时应该归于波导类），其引起的延时问题按上文说的判定准则来说也是没有问题的。
在一个系统中，最容易引起延时问题的就是低频的滚降和中高分频点附近的地方。

没有见到Blauert和Laws的原文，不知他们的实验条件。
这种对比的前提是要求有同样的平直的幅—频特性吗？
1 MS 的延时对应 34 CM 呀，高频延时的实验怎么作的，有点疑惑。

关于相位、群延时的可听度，这里有个实验很有意思。
差点找不到了，先放上来让大家参考参考。
http://www.music.miami.edu/programs/mue/Research/dkoya/thesis_abstract.htm
文中对相移的控制是通过一个或者几个全通滤波器来进行（详细见第3章），这样也会造成了某个窄带内的群延时特变。所以我估计Blauert和Laws可能也是通过类似的办法来研究的。

马上又找了一下，Blauert和Laws的文章找到，
粗看里面的示意图，用的就是全通滤波器。
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感谢热心勤奋的IMXP版主.
学学看.

这是篇硕士学位论文。应该算是比较面向实际的了。

与南大的硕士论文相比水平如何？

呵呵，这里就有南大的硕士吧？
那篇英文论文还是不错的，估计用来做硕士论文也足够合格。
既然是硕士，那当然有其刻苦、独到的地方，本人愚笨，不能妄加评论。

偶也找到一个AES论文的摘要。放上来供大家参考啰！

On t	he Audibility of Midrange Phase Distortion in Audio Systems
Author(s): Lipshitz, Stanley P.; Pocock, Mark; Vanderkooy, John
Abstract: The current state of our knowledge regarding the audible consequences of phase nonlinearities in the audio chain is surveyed, a series of experiments is described which the authors have conducted using a flexible system of all-pass networks carefully constructed for this purpose, and some conclusions are drawn regarding the audible effects of midrange phase distortions. It is known that the inner ear possesses nonlinearity (akin to an acoustic half-wave rectifier) in its mechanical-to-electrical transduction, and this would be expected to modify the signal on the acoustic nerve in a manner which depends upon the acoustic signal waveform, and so upon the relative phase relationships of the frequency components of this signal. Some of these effects have been known for over 30 years, and are quite audible on even very simple signals. Simple experiments are outlined to enable the readers to demonstrate these effects for themselves. Having satisfied ourselves that phase distortions can be audible, the types of phase distortions contributed by the various links in the audio chain are surveyed, and it is concluded that only the loudspeaker contributes significant midrange phase nonlinearities. Confining the investigation to the audibility of such phase nonlinearities in the midrange, circuitry is described which enables such effects to be assessed objectivbely fo their audible consequences. The experiments conducted so far lead to a number of conclusions. 1) Even quite small midrange phase nonlinearities can be audible on suitably chosen signals. 2) Audibility is far greater on headphones than on loudspeakers. 3) Simple acoustic signals generated anechoically display clear phase audibility on headphones. 4) On normal music or speech signals phase distortion appears not to be generally audible, although it was heard with 99% confidence on some recorded vocal material. It is clear that more work needs to be done to ascertain acceptable limits for the phase linearity of audio components穕imits which might become more stringent as improved recording/reproduction systems become available. It is stressed that none of these experiments thus far has indicated a present requirement for phase linearity in loudspeakers for the reproduction of music and speech.

沒辦法，為了學習，我只有拼命賺分了~~

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