Calculation of phase angle: phase difference, phase shift from time delay (time of arrival difference ITD) and frequency
http://www.sengpielaudio.com/calcula...delayphase.htm
可列印查看
Introducing signals
http://www.doctronics.co.uk/signals.htm
轉載本站 某網哥(給我的)的解釋..
一般人大概不太懂啥是相位..
意思是時間差.
例如兩人並行.步伐同樣大小.且同時起步.那就同向.
若起步時間有差異.那就不同向.
而音樂中.我們在乎的是全頻段不同的頻率是否同相?
再以上例來說(不是很精確的類比法).就是二個'大小"不同的人(高頻與低頻)並行.
但二人的速度都相同.起步時有時間差.因此二人之間就一前一後..
當走過擴大機.出來時.又變成怎樣?
當走到聆聽位置時.又如何了?
理想的相位頻率頻率響應..
應該是水平一條在正中央0度..(略去圖表.)
實際上都差很多.總是扭曲..
..通常高頻部份是單一喇叭擔單體發出.而且受空間影響比較小..
可以比較平順.不見得平直.可能是持續緩緩偏移...
中低頻受空間影響大.就總是亂七八糟...
這個在老喇叭kit中有很多可以玩的地方~~
我是在之前看殺音響講座中聽psycho兄的一段解釋才了解!
我也覺得相位是音樂還原是否良好相當關鍵的因素!
再如Yeh捨兄所言,錄音中很多的細節應當也都存在於各頻段當中,一但各頻段因為各種因素而不同相時,自然就會出現落差而出現各種問題...:|
相位應是聲波角度問題......
時間不一致是另一個議題
??
那時間不一致是什麼呢?:(
剛剛找的~
http://zh.wikipedia.org/zh-tw/%E7%9B%B8%E4%BD%8D
時間不一致,更正確的說是~相位差?!
希望帶出幾個問題,讓大家更清楚,小弟我是不太懂,測過但都是人家講解給我聽的
這裡應該不是說錄音的正確性,是說音響系統的
相位怎麼量
什麼工具
何為正確
有測量後圖示的案例嗎
如何為標準
正確的聽感該是如何(稍微就行,我了解網路討論最難就在這)
什麼會影響相位
如果有好心的網兄能提供相關訊息,希望Drunkenlife兄能在此版著墨一下
一起來唸書吧.............
這個就交給我了.............
這還有些前級是反向輸出的設計~~~也告訴用家其他設定與線材通通不用改動!!!
WHY??????
要先瞭解與確認正向、反相的意義.............
對於相位,我也是跟remo兄一樣,透過殺音響講座中psycho兄的解說才稍稍明瞭
但是真要我聽,個人還是不能很明確的分辨相位失真(sweat)
http://www.wretch.cc/blog/hchiehjung/3346093
這網頁的內容有一些益處,可以搭配著去設計及調整
phase
In electronic signaling, phase is a definition of the position of a point in time (instant) on a waveform cycle. A complete cycle is defined as 360 degrees of phase as shown in Illustration A below. Phase can also be an expression of relative displacement between or among waves having the same frequency .
Phase difference , also called phase angle , in degrees is conventionally defined as a number greater than -180, and less than or equal to +180. Leading phase refers to a wave that occurs "ahead" of another wave of the same frequency. Lagging phase refers to a wave that occurs "behind" another wave of the same frequency. When two signals differ in phase by -90 or +90 degrees, they are said to be in phase quadrature . When two waves differ in phase by 180 degrees (-180 is technically the same as +180), the waves are said to be in phase opposition . Illustration B shows two waves that are in phase quadrature. The wave depicted by the dashed line leads the wave represented by the solid line by 90 degrees.Phase is sometimes expressed in radians rather than in degrees. One radian of phase corresponds to approximately 57.3 degrees. Engineers and technicians generally use degrees; physicists more often use radians.The time interval for one degree of phase is inversely proportional to the frequency. If the frequency of a signal (in hertz ) is given by f , then the time t deg (in seconds) corresponding to one degree of phase is:
t deg = 1 / (360 f )The time t rad (in seconds) corresponding to one radian of phase is approximately:
很多人會讓很簡單的解釋,東拉西扯一堆毫無關連的東西,讓它變得很複雜
產品設計、空間是另外一回事,正常要怎麼做才會讓喇叭及器材相位一致呢?
咱們一個一個講.....
我跟唸書時代一樣,從頭看起...
What is phase?
Phase is a frequency dependent time delay. If all frequencies in a sound wave (music, for instance), are delayed by the same amount as they pass through a device, we call that device “phase linear.” A digital delay has this characteristic—it simply delays the sound as a whole, without altering the relationships of frequencies to each other. The human ear is insensitive to this kind of phase change of delay, as long as the delay is constant and we don’t have another signal to reference it to. The audio from a CD-player is always delayed due to processing, for instance, but it has no effect on our listening enjoyment.
http://www.earlevel.com/main/1996/10...tion-of-phase/
之前小葉給的判定極性的測試, 我用電腦喇叭完全聽不出來, 全部瞎猜......
其實我不太清楚大家是希望怎麼去"解決"相位問題....
這篇老paper可能幫得上忙吧,至少就第1.2.3點來講
www.bksv.com/doc/17-198.pdf
這段就說到,即使是Phase Linear,所有聲波的頻率都以一個固定的延遲時間通過人器材,在相對的基礎下我們還是可以查覺
舉例來說,你比較靠一邊的喇叭聽兩隻喇叭的聲音,即使你將在那個位置的聲音調成左右聲道一樣,你還是可以感覺到聽到的聲音跟坐在喇叭正中間是不同的
另外一個例子是我們將音樂延遲後混到正常沒有延遲的版本,若是一點點延遲的混音,會使頻率相互取消、若長一點的延遲就會變成echo
若將你的一隻喇叭反過來,將訊號反相,就可達到phase cancellation (一般人run喇叭的方法),在mono訊號與低頻的部份特別容易發現,喇叭的距離就比較沒關係了
Relative phase
Now, even if the phase is linear (simply an overall delay), we can easily detect a phase difference if we have a reference. For instance, you can get closer to one of your stereo speakers than the other; even if you use the stereo balance control to even the relative loudness between speakers, it won’t sound the same as being equidistance between them.
Another obvious case is when we have a direct reference to compare to. When you delay music and mix it with the un-delayed version, for instance, it’s easy to hear the effect; short delays cause frequency-dependent cancellation between the two signals, while longer delays result in an obvious echo.
If you connect one of your stereo speakers up backwards, inverting the signal, you’ll get phase cancellation between many harmonic components simultaneously as they cancel in the air. This is particularly noticeable with mono input and at low frequencies, where the distance between the speakers has less effect.
其實我覺得相位問題一但發生很難解決
不過我們至少要能知道與瞭解相位問題
考慮到邊界造成的效果, 問題又複雜起來......
在來看看一般的Case,不是Linear Phase,而是frequency-dependent delay,跟頻率有關的延遲
我們能聽出相同訊號,但是相位不同的差異嗎?
答案是No and Yes
相位錯誤(Phase Error),在真實社會,這個通常是指固定的,且影響一群的頻率。
NO => 人耳對聲音固定相位的改變是不敏感的,你聽不出來聲波只有相位的不同
Yes => 如果是動態的改變,那就會影響聲音了,音樂正是動態的聲波形式,其影響程度視相位的角度 (phase error)與其所影響的範圍、音樂本身來決定
The general case
Having dispensed with linear phase, let’s look at the more general case of phase as a frequency-dependent delay.
Does it seem likely that we could hear the difference between a music signal and the same signal with altered phase?
First, I should point out that phase error, in the real world, is typically constant and affects a group of frequencies, usually by progressive amounts. By “constant”, I mean that the phase error is not moving around, as in the effect a phase shifter device is designed to produce. By “group of frequencies”, I mean that it’s typically not a signal frequency that’s shifted, or unrelated frequencies; phase shift typically “smears” an area of the music spectrum.
Back to the question: Does it seem likely that we could hear the difference between an audio signal and the same signal with altered phase? The answer is… No… and ultimately Yes.
No: The human ear is insensitive to a constant relative phase change in a static waveform. For instance, you cannot here the difference between a steady sawtooth wave (which contains all harmonic frequencies) and a waveform that contains the same harmonic content but with the phase of the harmonics delayed by various (but constant) amounts. The second waveform would not look like a sawtooth on an oscilloscope, but you would not be able to hear the difference. And this is true no matter how ridiculous you get with the phase shifting.
Yes: Dynamically changing waveforms are a different matter. In particular, it’s not only reasonable, but easy to demonstrate (at least under artificially produced conditions) that musical transients (pluck, ding, tap) can be severely damaged by phase shift. Many frequencies of short duration combine to produce a transient, and phase shift smears their time relationship, turning a “tock!” into a “thwock!”.
Because music is a dynamic waveform, the answer has to be “yes”—phase shift can indeed affect the sound. The second part is “how much?” Certainly, that is a tougher question. It depends on the degree or phase error, the area of the spectrum it occupies, and the music itself. Clearly we can tolerate phase shift to a degree. All forms of analog equalization—such as on mixing consoles—impart significant phase shift. It’s probably wise, though, to minimize phase shift where we can.
不要將極性(polarity)與相位(Phase)搞混喔...............
polarity我是真的聽不太出來, 測試片那種很刻意的訊號可以
但是如果是cd player切換正反向 以及 小葉你給的那個網址 我是真的聽不出來