Autodesk 64006-051108-9001 User Guide - Page 87

The Audio Tab 79 High Pass The High Pass filter removes all frequencies at or below the given value in kHz. Like the Low Pass filter, this filter gets its name from the fact that high frequencies (above the given value) pass through the filter unaltered. This filter is generally used to eliminate specific low frequencies associated with background noise, such as the low rumble of ventilation systems. To use this filter, specify the frequency (in Hz) below which you want the signal to be silent. Note: The Notch filter is often a better choice than High Pass if you know the frequency at which the unwanted noise is occurring. The Notch filter enables you to selectively target a specific frequency without removing all the frequencies below it. If set too high, the High Pass filter can make the audio sound tinny as it removes too many of the low (bass) frequencies from a source. Noise Removal Unwanted noise is common in recorded audio signals. Noise is often inadvertently added to the signal during the actual recording (camera noise, hard drive noise, fluorescent light hum) and during capture (line noise from low-quality capture hardware). You may not notice minor noise in your signal, but even minor audio noise degrades encoding and should be removed. To help remove common types of audio noise, Cleaner provides an Adaptive Noise Removal filter. This filter removes random white noise, such as hiss and general static, as well as more structured colored noise, such as power line noise, ventilation system hum and hard drive noise. The Noise Removal filter works well for many types of noise, including line noise. However, if only line noise is present, try the Notch filter first because it removes only a specific frequency without altering any other parts of the audio. For most material, using one of the presets is a good solution. With very noisy or difficult source material, the Custom option may be helpful. More difficult material may also benefit from the additional use of the High Pass, Low Pass, Notch and Noise Gate filters. Noise Removal Custom Setting The Noise Removal filter > Custom option enables you to specify the threshold at which the filter operates. The higher the number chosen, the more pronounced the effect on the audio. Using high amounts of noise reduction can introduce warbling artifacts into the audio track. High noise-reduction levels may also reduce the overall volume of the signal, so you may want to boost the volume when using higher settings.