Adobe 22011292 User Guide - Page 187

ADOBE AUDITION 173 User Guide • Uncheck Log Scale to divide the graph linearly, with each 1000kHz (for example) taking up the same amount of horizontal width. Live Update Select or deselect this option: • When you check this option, the noise profile plot updates as control points are moved around on the graph. • With Live Update unchecked, the profile plot is only updated when a control point is placed in its new location. Noise Reduction Level Use this slider to manually adjust the amount of noise reduction (measured in percent) to be applied to the waveform or selection. You may also enter the desired amount directly in the text box to the right of the slider. Note: Depending on the original waveform and the type of noise removed, high noise reduction levels can sometimes cause the remaining audio to have a "flange-y" or "phase-y" quality. If this happens undo the effect and try a lower setting. Noise Reduction Settings Set the following options: • FFT Size: This parameter causes the most drastic changes in quality. It determines the number of individual frequency bands that are analyzed. The noise in each frequency band is treated separately, so the more bands you have, the finer frequency detail you get in removing noise. For example, if there's a 120Hz hum, but not many frequency bands, frequencies from 80Hz on up to 160Hz may be affected. With more bands, there's less spacing between bands, so the actual noise can be detected and removed with more precision. However, with too many bands, time slurring occurs, which can make the result sound reverberant or "echoey" (with pre- and post-echoes). So the tradeoff is frequency resolution vs. time resolution, with lower FFT sizes giving better time resolution and higher FFT sizes giving better frequency resolution. Good settings for FFT Size range from 4096 to 12000. • Remove Noise/Keep Only Noise: For normal operation, choose Remove Noise. If for some reason you want to extract the noise for other purposes, choose Keep Only Noise. All the audio will be removed, leaving only noise. • Reduce by: Lowering this value (measured in dB) may help reduce some bubbly background effects. Settings between 5dB and 100dB are recommended. • Precision Factor: This value affects distortions in amplitude. With values of 3 or less, the FFT is performed in giant blocks that aren't very continuous between the blocks. This means that after each block is processed, there can be a drop or spike in volume at the interval between blocks. Values of 5 and up work best. Beyond 10 or so, there is no noticeable change in quality-only in the time it takes to compute. Try using 5 or 7, as odd numbers are best for symmetric properties. • Smoothing Amount: This takes into account the standard deviation, or variance, of the noise signal at each band. Bands that vary greatly when analyzed (such as white noise) will be smoothed differently than constant bands (like a 60 cycle hum). Generally, increasing the smoothing amount (up to 2 or so) will reduce the "burbly" background artifacts at the expense of raising the overall background broadband noise level.