Noise Reduction
Noise Reduction can dramatically reduce background and general broad band noise
with minimal reduction in signal quality. It can also remove tape hiss, microphone
background noise, 60 cycle hum, or any noise that is constant throughout the
duration of your waveform. The amount of reduction required depends upon the
type of background noise, and the allowable loss in the quality of the signal
that is to be kept. In general, one should be able to attain increases in Signal
to Noise ratios of 5dB to 20dB (noise is reduced 21dB and signal 1dB for example).
Noise reduction includes
- Click/Pop Eliminator - works by searching for anomalies
in the audio data that could be construed as clicks or pops (Detection), and
then replacing or repairing the damaged location (Correction). Using the Click/Pop
Eliminator is more accurate than just cutting out the click, or replacing
the data with a straight line.
- Clip Restoration filter - used to remove the evil occurrences
of clipping from your waveform by actually “filling in” the clipped
segments of the waveform. Clipping is a phenomenon that occurs in digital
audio when the amplitude value of a signal exceeds the maximum level that
can be represented by the current bit resolution (i.e. 256 steps in 8-bit
audio). This can happen when the source recording levels were simply too high.
Clipping causes the signal to distort, and appears in the waveform display
as a "chopping-off" of the top or bottom of the waveform. The audible
result is a static-like distortion.
- Hiss Reduction - removes material in all frequencies that
are below a certain threshold (generally the noise floor or hiss level). If
audio has a constant background hiss (noise can removed more effectively than
hums or whines) then that hiss can be "noise gated", or removed
completely. Any audio in any frequency band louder than the cutoff level will
remain untouched; literally carves out annoying hiss from cassette recordings,
record albums (after click/pop removal), or microphone recordings.
