Compression-release ("Jake") braking, a form of engine braking used almost exclusively on diesel engines, produces extreme amounts of noise pollution if there is no muffler on the intake manifold of the engine. Anecdotally, it sounds similar to a jackhammer, however the loudness is between 10 and 20 times the sound pressure level of a jackhammer (10 to 13 dB greater). Numerous cities, municipalities, states, and provinces have banned the use of unmuffled compression brakes, which are typically only legal in roads away from populations. In Australia, traffic enforcement cameras are currently being tested that automatically photograph heavy vehicles that use compression braking.