Waveform and Phase

Since many people asked me on this topic. I can write short paragraphs about this topic with music samples as example.

  1. The following is the original file of my own Jazz album. I hope it sounds decent for you. This is called a Waveform view, it shows you the music as different levels in waveform presentation. There are two waveforms in stereo file. Upper part is Left channel, lower part is Right channel. You can download the song from here. 以下是我自己的爵士原音專輯的母帶音樂檔案。這是個波形圖,它用波形呈現顯示音樂中大小音量。你看到立體聲文件中兩個波形 (白色部份)。上半部分是左聲道,下部是右聲道。你可以從這裡下載這段歌曲。 (AJP-01 Autumn Leaves-Original.aif)

01-Original

2. I inverted both left/right channels phases and created a new file. You can download the Inverted Phase file to listen for reference. 我把左右聲道兩個相位反轉。您也可以下載這個相位反轉音樂檔案作參考 (AJP-01 Autumn Leaves-Both-Ch_Inverted_Phase.aif)

02-Original-InvertedPhanse

3. The following photo I line up both sound file on the timeline. They look similar from this view. The blue file is the original stereo file, the yellow file is the inverted phase file. 下面這張是我把兩個音樂檔案排列一起。從這個角度他們看起來差不多。藍色是原本立體聲檔案,黃色是相位反轉的音樂檔案。

03-Two-Waveforms

4. If you zoom in to any section and look carefully, you will see the waveforms are inverted. You can see the highlighted section. The blue file upper section (left channel) waveforms are pointing downward, while the yellow selected section of left channel waveforms are pointing upward. 如果放大到任何部分,並仔細看,你會看到波形反轉。你可以看到藍色文件上半部分(左聲道)波形朝下,而相位反轉的音樂檔案左聲道波形選取了橙色部份卻指向上方。

04-Zoom-Up-Down

5. If we zoom in closer, you can see the waveform of both files are exactly inverted at the same level, same time position. 如果我們再縮小觀察波形圖,你可以看到這兩個音樂檔案的波形在同一級別,同一時間位置但是剛剛是反轉的。

05-MoreZoom_in

6. In digital world we have a term call “null-test” which we check if two digital files are perfectly identical to each other. Null-test is made the same way we did above to invert just one file phase and mix them together. Follow is the “null-test” result when I mix two files together. Since two files are opposite phases, when they mix (add up together) they will cancel out each other perfectly. The result file is completely zero. You may download the mixed file and listen by yourself. (AJP-01 Autumn Leaves-Null-Mixed.aif) You can also use the above 2 files to test your own null. 在數碼工程世界中,我們有一個術語叫“null test 空測試” 檢查兩個數碼檔案是完全彼此相同。null test 跟我們上面做的方式一樣,反轉其中的一個文件,之後把他們兩個數碼檔案混合一起。下面這張照是“null test 空測試”結果。由於這兩個檔案是相反,當他們混合在一起,他們將完美地互相抵消。結果混合檔案是完全為零。您可以下載這個混合檔案。 您也可以使用上面的2個音樂檔案來測試自己的null test。

06-Null

7. Speaking of fun I included one sound file for your reference. The following file is just inverted Left channel. You should hear a weird out of phase sound. (AJP-01 Autumn Leaves-Left-Ch_Inverted_Phase.aif) 我提供一個音樂檔案給大家參考。這個音樂檔案只是倒轉了左聲道。你應該聽到一個奇怪異相的聲音。

07-LeftCh_Inverted_Phase


Audio engineer and entrepreneur. Major focus on audio distribution business in Asia region. Currently handling more than a dozen of highend consumer and professional audio brands in the area. Headquarter is located in Hong Kong, with branches in China, Taiwan and Japan.

Leave a Reply

INSTAGRAM
Kent Poon's Instagram