Apple Using WaveBurner Logic Pro 7.1 User Manual
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Denoiser
You can eliminate or reduce many kinds of low-level noise (noise floor) from an audio
signal with the Denoiser. The main parameters of the Denoiser are Threshold, Reduce,
and Noise Type. The Threshold parameter determines the level below which signals are
interpreted as noise floor. The recommended method for setting the Threshold is to
find a passage where only noise is audible, then set the Threshold so that signals at this
volume level are filtered out.
The Reduce parameter sets the level that the noise floor is reduced to. You use the
Noise Type parameter to determine the type of noise that the Denoiser will reduce.
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, sibilance, 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 effected. Use of the Denoiser
at extreme (or high) settings may produce artifacts that sound like tinkling glass, which
is usually less desirable than the existing noise.
There are three smoothing parameters that you can use to minimize such artifacts:
Frequency smoothing, Time smoothing, and (Level) Transition smoothing.
The higher the Frequency smoothing parameter is set, the more it will smooth
neighboring frequency bands to avoid artifacts during the noise reduction process.
Adjustment of the Time smoothing slider sets the amount of time the Denoiser takes to
reach maximum noise reduction. By adjusting the Level Transition smoothing slider,
you can set a transition factor between volume jumps. The higher the Transition
smoothing parameter is set, the more it will smooth sudden level changes, thus
avoiding artifacts during the noise reduction process.