Apple Soundtrack Pro 3 - Manual (Page 282)

Denoiser
Using the Denoiser, you can eliminate or reduce many kinds of low-level noise (noise
floor) from an audio signal. The main parameters of the Denoiser are Threshold, Reduce,
and Noise Type. The Threshold parameter sets how high the noise floor is for the audio
signal. The recommended method for setting the Threshold is to find a passage where
you hear only noise, then set the Threshold so that signals at this volume level are filtered
out.
The Reduce parameter sets the level to which the noise floor is reduced. You use the
Noise Type parameter to set the type of noise that the Denoiser reduces. There are three
choices of noise type:
• Setting the Noise Type to 0 (zero) causes the Denoiser to reduce “white noise” (all
frequencies reduced equally).
• Setting the Noise Type to a positive value causes the Denoiser to reduce “pink noise”
(harmonic noise; greater bass response).
• Setting the Noise Type to a negative value causes the Denoiser to reduce “blue noise”
(hiss, sibilants, tape noise).
The Denoiser recognizes frequency bands with a lower volume and less complex harmonic
structure, and then reduces them to the desired dB value. This method is not completely
precise, and neighboring frequencies are also reduced. Using the Denoiser at too-high
settings can produce the “glass-noise” effect, which is usually less desirable than the
existing noise.
There are three smoothing parameters that you can use to minimize the “glass-noise”
effect: Frequency smoothing, Time smoothing, and Level smoothing. Raising the Frequency
smoothing slider results in a smoother transition of denoising to the neighboring
frequencies. When the Denoiser recognizes that only noise is present in a certain frequency
band, the higher the Frequency Smoothing parameter is set, the more it will also change
the neighboring frequency bands to avoid glass noise.
By adjusting the Time smoothing slider, you can set the amount of time the Denoiser
takes to reach maximum noise reduction. By adjusting the Level smoothing slider, you
can set a factor for a smoother transition between adjacent volume levels. When the
Denoiser recognizes that only noise is present in a certain volume range, the higher the
Transition smoothing parameter is set, the more it will also change similar level values
to avoid glass noise.
282 Chapter 10 Working with Audio Effects