What type of audio processor limits the level when the input signal exceeds a certain threshold?

The correct answer is a limiter, which is a type of audio processor specifically designed to control the dynamic range of a sound signal. Limiters work by allowing signals to exceed a certain predefined threshold only to a limited extent, effectively preventing any signal peaks from going above this level. This is crucial in various audio applications to prevent distortion and clipping, which can occur when signals are too loud.

While compressors also manage audio levels, they reduce the dynamic range in a more gradual manner and do not restrict the signal as strictly as limiters. Equalizers modify frequency response rather than dynamics, and reverbs add spatial effects to the audio signal without controlling volume levels. A limiter, therefore, plays a distinct and vital role in mastering and live sound reinforcement, where maintaining audio integrity is essential.