Brickwall limiters have a huge ratio, typically infinity to 1. Anything louder than the threshold is completely squashed. A regular limiter will mostly keep the volume at or below the threshold. But some sound may still pass the threshold.

What does brickwall limiter do?

A limiter set up with such a high ratio (often “infinity”:1) that a hard “ceiling” is imposed on signal level – once the signal reaches the threshold, it can go no further. Brickwall limiters are commonly used to prevent digital overs and for other types of overload protection.

What does an audio limiter do?

As a creative tool, a limiter can boost the perceived volume of a certain sound. It can also be used to restrain unpredictable effects or automated sounds that have too much dynamic range. You'd simply be using the Limiter as a heavy-duty Compressor (a Compressor with a very high ratio).