Editing WAVE file
How to make preview sound?
Here is a general flow;
Here is the example way to do the step (b)-(d) by using Audacity.
1. At first, open the song file by Audacity. Then, cut-off the non-climax part a little by little, like the figure below. (Choose the deleting part by dragging, then push "Delete" to delete that part). This figure shows that deletes the long-tail-part. Usually, the first delete will be the big one, and second/third... deletion become smaller. To delete small part, it's useful to enlarge the display of wave, by Ctrl+MouseWheel.
4. Add silence to the tail of the data. First. click any part of the wave to release the selection. Next, click the tail of the wave to set the silence-insertion-position to the tail. Then click "Generate" - "Silence".
8. At last, save the a wave file. Save it by "File" - "Export". You can choose "Export as WAV" or "Export as OGG". If you may edit the file later, you should save it as WAV. If not, you should save it as OGG.
What is Normalize?
For example, 16bit-wave data can use the value of -32768-32767. However, usually, practical data does not use all range of -32768-32768. (ex. -8000-5000, etc)
The actual range depends on each wave data, but anyway the amplitude means the volume. So, as the result, "Each song data has different volumes."
To prevent it, all wave data should use all range (-32768-32767). This operation is usually called as "Normalize." You can do it in Audacity by "Effect" - "Normalize".
Normalized song data's volumes are almost all the same.
# However, in real, normalized data have different sound pressure, so you'll feel the different volume. To match the volume of your feeling, you should use "Effect" - "Compressor" to match sound pressure to other sounds.
Petit noise occurs at the tail of the sound. How to remove it?
The cause of petit-noise at the tail of the sound is, "suddenly change the volume at the tail of the sound".
The figure below show the typical case which occurs the petit noise at the tail of the wave. The last value of the big, and when the playback ends, the value become zero. Big value become zero drastically. This is the cause of the noise.
To solve it, set the last value near zero. To realize it, you can choose 2 ways;
Here is the step to do the second way by Audacity.
After cut-and-paste the waveform, petit-noise occurs. How to prevent it ?
When you cut-and-paste the waveform, both beginning/terminating point must be "zero crossing point"
"Zero crossing point" means the point which the value become "minus -> plus" or "plus -> minus". Shortly to say "crossing the zero".
If you cut the waveform from/to the zero crossing points, the big difference of value does not occur near the cut-off points. As the result, drastic change of value does not happen....it means no noise happens.
In Audacity, you can use "At Zero Crossings" feature. First roughly choose the area, then click "Select" - "At Zero Crossings". As the result, selected point (from/to) become zero-crossing point".
How to change the pitch of the sound?
You can change it by Audacity.
How to invert (swap) the left/right sound?
You can do it by Audacity.