Intro to levels effects in Final Cut Pro
The levels effects control the perceived loudness of your audio, add focus and punch to clips, and optimize the sound for playback in different situations.
The dynamic range of an audio signal is the range between the softest and loudest parts of the signal—technically, between the lowest and highest amplitudes. Dynamics processors enable you to adjust the dynamic range of individual audio clips. This can be to increase the perceived loudness or to highlight the most important sounds, while ensuring that softer sounds are not lost in the mix.
There are four types of dynamics processors included in Final Cut Pro, each used for different audio processing tasks.
Compressors: Final Cut Pro features a number of downward compressors. These behave like an automatic volume control, lowering the volume whenever it rises above a certain level, called the threshold. So, why would you want to reduce the dynamic level?
By reducing the highest parts of the signal, called peaks, a compressor raises the overall level of the signal, increasing the perceived volume. This gives the signal more focus by making the louder (foreground) parts stand out, while keeping the softer background parts from becoming inaudible. Compression also tends to make sounds tighter or punchier because transients are emphasized, depending on attack and release settings, and because the maximum volume is reached more swiftly.
In addition, compression can make a project sound better when played back in different audio environments. For example, the speakers of a television set or in a car typically have a narrower dynamic range than the sound system in a cinema. Compressing the overall mix can help make the sound fuller and clearer in lower-fidelity playback situations.
Compressors are typically used on dialogue clips to make the speech more intelligible in an overall mix. They are also commonly used on music and sound effects clips, but they are rarely used on ambience clips.
Some compressors—multiband compressors—can divide the incoming signal into different frequency bands and apply different compression settings to each band. This helps to achieve the maximum level without introducing compression artifacts. Multiband compression is typically used on an overall mix.
Expanders: Expanders are similar to compressors, except that they raise, rather than lower, the signal when it exceeds the threshold. Expanders are used to add life to audio signals.
Limiters: Limiters—also called peak limiters—work in a similar way to compressors in that they reduce the audio signal when it exceeds a set threshold. The difference is that whereas a compressor gradually lowers signal levels that exceed the threshold, a limiter quickly reduces any signal louder than the threshold to the threshold level. The main use of a limiter is to prevent clipping while preserving the maximum overall signal level.
Noise gates: Noise gates alter the signal in a way that is opposite to that used by compressors or limiters. Whereas a compressor lowers the level when the signal is louder than the threshold, a noise gate lowers the signal level whenever it falls below the threshold. Louder sounds pass through unchanged, but softer sounds, such as ambient noise or the decay of a sustained instrument, are cut off. Noise gates are often used to eliminate low-level noise or hum from an audio signal.