Adobe AUDITION 3 User Manual page 154

For quick, general-purpose hiss reduction, a complete noise floor graph isn't always necessary. In many cases, you
can simply reset the graph to an even level and manipulate the Noise Floor Adjust slider.
Fine-tunes the noise floor until the appropriate amount of hiss reduction and quality level is
Noise Floor Adjust
achieved.
Specifies a transform size. In general, sizes from 3000 to 6000 work best.
FFT Size
Lower FFT sizes (2048 and below) result in better time response (less swooshing before cymbal hits, for example),
but they can produce poorer frequency resolution, creating hollow or flanged sounds.
Higher FFT sizes (12,000 and above) might cause swooshing, reverb, and drawn out background tones, but they
produce very accurate frequency resolution.
Determines the accuracy of hiss reduction in the time domain and affects the decay rate of spectral
Precision Factor
components below the previous hiss level. (See Spectral Decay Rate.) Typical values range from 7 to 14.
Larger values generally produce better results and slower processing speeds. Values over 20 don't ordinarily improve
quality any further.
Lower values might result in a few milliseconds of hiss before and after the louder parts of audio.
Produces a slow transition in hiss reduction instead of an abrupt change from no reduction to the
Transition Width
reduced hiss level. Values from 5 to 10 usually achieve good results.
If the value is too high, some hiss may remain after processing.
If the value is too low, other background artifacts might be heard.
When audio is encountered above the estimated noise floor, determines how much audio in the
Spectral Decay Rate
same frequency band is assumed to follow. With low values, less audio is assumed to follow, and the carving function
will cut more closely in time to the frequencies being kept. Values of 40% to 75% work best.
If the value is too high (above 90%), unnaturally long tails and reverbs might be heard.
If the value is too low, background bubbly effects might be heard, and music might sound artificial.
Sets the level of hiss reduction for audio below the noise floor.
Reduce Hiss By
With higher values (especially above 20 dB) dramatic hiss reduction can be achieved, but the remaining audio might
become distorted.
With lower values, not as much noise is removed, and the original audio signal stays relatively undisturbed.
Remove Hiss, Keep Only Hiss
Noise Reduction effect (Edit View only)
The Restoration > Noise Reduction effect dramatically reduces background and broadband noise with a minimal
reduction in signal quality. This effect can remove a wide range of noise, including tape hiss, microphone
background noise, 60-cycle hum, or any noise that is constant throughout a waveform.
The proper amount of noise reduction depends upon the type of background noise and the acceptable loss in quality
for the remaining signal. In general, you can increase the signal-to-noise ratio by 5 to 20 dB and retain high audio
quality.
Removes hiss or removes all audio except for hiss.
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User Guide