The number of tickets issued for noisy vehicles has been falling, which police say is partly due to the effect on enforcement of the Canterbury earthquakes.
Almost 13,000 infringements were recorded in the past five years.
But ticket numbers have been trending down since 2008, when almost 4000 offences were detected, to just over 1300 last year.
Motorists and motorcyclists can be fined or given demerit points for exceeding set levels for exhaust noise, which range between 90 and 100 decibels.
Acting national road policing manager Superintendent Rob Morgan says changes to legislation have helped get noisy vehicles off the road.
The Canterbury earthquakes are also a factor, as police time has been taken up with duties other than noisy vehicle enforcement.
Meanwhile, the number of tickets issued to motorists for smokey exhausts has also fallen.
The number of infringements has dropped every year since 2007, when 228 tickets were issued, to 107 last year.
A fine of $150 can be imposed when excessive smoke, or vapour, is emitted from their vehicle for more than 10 seconds.
Superintendent Morgan says the drop is as a result of enforcement and tougher exhaust standards.
