Transportation officials are looking to expand the use of photo enforcement to cash in on motorists who blast their stereos or use modified, high-performance exhausts. At least one agency has expressed interest in a ticketing system developed by Acoustic Research Laboratories, a New South Wales company that developed acoustic detection equipment for the Australian Navy.

The fully automated setup mails traffic citations to passing vehicles that exceed a predetermined noise threshold. It can detect loud subwoofers, a noisy exhaust, or even an inopportune honk of the horn.

A combination of sound level meters, cameras and computer processors identify these targets of opportunity. Separate microphone and video modules are pole-mounted in waterproof boxes that communicate with a laptop control unit using WiFi. The manufacturer claims that the system distinguishes predetermined trigger sounds from general background road noise. Once the system is configured, it will generate up to 10,000 tickets before the on-board hard drive is filled. A 10-second video and audio clip is stored for each incident.

Similar red light camera and photo radar technology has generated billions of dollars worldwide. In Washington, DC alone, cameras billed drivers more than $171 million since 1999.