Fix silence detection default threshold (#18649)
Fixes #18003.
Summary of the issue:
The default threshold values for signed integer types are incorrect, becoming twice as large, causing more parts to be trimmed than expected.
Description of user facing changes:
The excessive trimming will be fixed.
Description of developer facing changes:
None.
Description of development approach:
WaveFormat::defaultThreshold should use 1 / 2^10 or 0.0009765625 as the threshold value for all types.
The current implementation handles floating points and unsigned integers correctly, but fails to differentiate the signedness, so signed integer types will have a threshold value that's twice as large.
The solution is to replace the case-by-case implementation to a more general and correct max() / (1 << 10).
