Adobe 22011292 User Guide - Page 333

ADOBE AUDITION 319 User Guide • Attack Time: the attack time (measured in milliseconds) applied when retrieving the current amplitude information. Attack Time determines the time in milliseconds that it takes for the processed output signal to reach its specified output volume. If there's suddenly a quiet portion that drops 30dB, it will take the amount of time specified in this field before the output actually drops to its corresponding volume level. If the sum of the Attack and Release times is too short (less than 20 milliseconds total), audible effects (such as a "vibrating" sound) can be heard at around 1000 Hz/ms total. For example, if the Attack and Release times are each set to 5 milliseconds (making 10 milliseconds total), then a vibrating sound at 100Hz will be heard. Thus, a total value of about 30 milliseconds is about as low as you can go without introducing these effects. • Release Time is the release time (measured in milliseconds) applied when retrieving the current amplitude information. Release Time is the time it takes the end of a previous output level to reach the specified output volume. For example, where the Attack is the time it takes for the start of a pulse to reach the desired output volume, the Release is the time it takes for the end of the pulse to reach the desired level. • Peak/RMS: Two methods of graph interpretation are provided for this effect: Peak and RMS. • Peak Mode is a little more difficult to use than RMS, and is considered by many to be outdated. It equates to the RMS value times two. That is, if the RM value is -20dB, then the equivalent peak value will be -40dB. This occurs because the RMS value calculated was mapped to a peak sample value for output. This method is basically here for backward compatibility. • RMS is the graph interpretation method that more closely matches the way people hear volume. This mode causes the output to be exactly the RMS amplitude that's specified in the graph. For instance, a limiter (flat horizontal line) at -10dB causes the RMS amplitude of the result to average -10dB (where 0dB is a maximum amplitude sine wave without clipping). Low Cutoff This is the lowest frequency that dynamics processing will affect. You can define a band, or range, to which compression or expansion is applied, within the current frequency range. The Low Cutoff point is the bottom boundary in defining this band. For example, with values of 1000 for Low Cutoff and 5000 for High Cutoff, dynamics processing only affects audio in the frequency range of 1kHz to 5kHz. To use the entire frequency range of the source material, leave this setting at 0. High Cutoff This is the highest frequency that dynamics processing will affect. You can define a band, or range, to which compression or expansion is applied, within the current frequency range. The High Cutoff point is the bottom boundary in defining this band. For example, with values of 2000 for Low Cutoff and 9000 for High Cutoff, dynamics processing only affects audio in the frequency range of 2kHz to 9kHz. To use the entire frequency range of the source material, this setting should be a one-half of the current sample rate (24000 for 48kHz, 11025 for 22kHz, etc.). Lookahead Time Lookahead Time is used to handle sharp spikes that might occur at the onset of a louder signal. At times, and for brief instances, these onsets can go beyond the limits of your compressor settings, which may be desirable in certain compression scenarios since it can enhance the impact of, say, a drum hit. However, this is obviously not desirable if you're using limiting in order to reduce the maximum amplitude of the audio.