It may look like a speed camera and it may take photographs like a speed camera, but it's not a speed camera. The boxy camera installed on Mt Ousley Rd last week has been set up to catch out the noisy, vibrating "bark" caused by trucks' engine brakes.The noise detection camera is part of a trial of new equipment set to test whether trucks are adhering to the approved national engine brake noise standard, established by the the RTA and the National Transport Commission in August last year."Noise from engine compression brakes is a particular source of concern and complaint for many NSW residents," an RTA spokesman said."The RTA has been working with the National Transport Commission to help develop a standard for in-service engine brake noise. A national standard has been approved for use."The loud bark, which is not measured in decibels, but algorithms, is caused by engine brakes on heavy vehicles fitted with worn, defective or inferior mufflers. When the Mercury visited the site of the noise detection camera, on the southbound bend just before the New Mt Pleasant Rd overpass, it heard one in five trucks using compression brakes, despite signs warning truck-drivers to limit their use. The RTA said trucks caught not adhering to the national standard would be warned, but not penalised. "Operators detected exceeding the standard are sent a letter advising that they take appropriate action to modify their behaviour or the vehicle," the RTA spokesman said.