Concretely, the gain is applied after decoding and the file is re-encoded, which costs one generation — so set the level you want in one pass rather than nudging it repeatedly, and use normalisation instead if what you want is a consistent perceived loudness. You set a gain in decibels or as a percentage and it is applied uniformly across the whole file.
Will boosting the volume distort the audio?
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Only if it clips. Headroom is checked before the file is written, so a boost that would push peaks past full scale is flagged rather than silently squared off. If the recording is quiet because it is noisy, boosting raises the noise too.
Does the source format matter?
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It does. WMA is Windows Media Audio, tied to the Microsoft stack and poorly supported on phones. That decides whether a gain change is an exact edit of the samples or has to go through a re-encode.
Anything specific to WMA to know?
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Yes — WMA tooling outside the Microsoft stack is thin, which is why browser-side work on it is usually more reliable than a desktop app. Relevant if you plan to adjust the level more than once.
Should I use volume or normalisation?
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Use volume when you know exactly how much louder or quieter you want it. Use normalisation when you want a set of files to end up at the same perceived loudness — that is a measurement problem, not a fixed gain, and applying one when you meant the other is the usual mistake.
Can I adjust a whole batch to the same gain?
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Yes, though be careful what you are asking for: the same gain on files recorded at different levels keeps them at different levels. If you want them to match, normalise instead.
