To 'trim' is to cut off the beginning and the end of the file so only the selected region remains. This is useful when you have just recorded a file but there is silence or noise before the start or after the end.
Select the part of the file you want to keep and then press Ctrl+T.
Trim Start (Ctrl+M)
To delete everything before the current position select Edit -> Trim -> Trim Start.
Trim End (Ctrl+E)
To delete everything after the current position select Edit -> Trim -> Trim End.
Auto Trim Silence from Start and End
Auto Trim removes the silence at the beginning and the end of the selected region without you needing to find the exact position where recording starts.
Auto Trim works by scanning the region for the peak level then removing the start and end that is below the Auto Trim Threshold Level below the peak. The Auto Trim Threshold Level can be adjusted through the Tools -> Options -> Audio Processing tab. The default is -20 dB. Increase this to -15 in noisy environments. Decrease to -24 in a studio.
This feature will not be useful in an environment with high background noise, as WavePad will be unable to differentiate between the background sounds and your voice.
Auto Trim applies to the selected region. Often you might want to Select All (Ctrl+A) first before using Auto Trim.
The Trim Silences function can be used to remove or shorten silent regions. It is similar to Auto Trim, but provides more advanced functionality. It works by scanning the selected region for the peak level, then searching for regions that are the Auto Trim Threshold level below that peak. These 'silences' can then be removed, or shortened.
- Silence Threshold:
- This is the level below the peak that will be considered silence. The default is -20dB. Increase this to -15 in noisy environments, or decrease it to -24 in a studio.
- Remove only leading and trailing silence:
- Check this if you only want to remove leading and trailing silence. This will make Trim Silences behave like AutoTrim, but it will do a more thorough, albeit slower, analysis.
- Minimum Silence Length:
- This is the time, in seconds, that a region must be below the Silence Threshold before it will be considered truly silent. The minimum is set to 25ms, which is half the wavelength of a sound at 20Hz, the lowest audible sound. If we were to remove silences shorter than this then we would start to risk losing non-silent audio in a low point of its wave. The default is 200ms. Note that this minimum does not apply to silences at the start and end of the file. These will be identified as silence regardless of length.
- New Silence Length:
- In some cases you may want to replace long periods of silence with shorter periods. Choose a fixed length to reduce these longer periods to. Audio will be removed from the middle of the original period, to avoid clipping the ends of the audio surrounding the silence. Set this to 0 to completely remove silences. Note that silent regions will not be extended to meet this length, only reduced to it. See also 'Add Multiple of Original Silence' below.
- Add Multiple of Original Silence:
- This is a multiple of the original silence, to be added to the New Silence Length (see above). This allows you to set the new silence time based on the original silence time. Set this to 0 to completely remove silences, assuming that 'New Silence Length' is also set to 0.