Edmonton police officers tested one of their own motorcycles during a media demonstration in June. ((CBC))

Fifty of the 115 tickets issued under Edmonton's new noisy-motorcycle bylaw are being challenged in court.

The bylaw amendment, which took effect July 1, allows police to issue $250 fines to anyone with a motorcycle louder than 92 decibels while idling and 96 decibels while the engine is revving.

The first and only case tried so far by a justice of the peace resulted in the biker having the ticket dismissed, said city prosecutor Scott McAnsh.

"The commissioner held that he had reasonable doubt as to the accuracy of the sound meter because we didn't [present] enough evidence on recent testing or on training," McAnsh said.

McAnsh has that information but he thought the oral evidence given by the police officer who administered the sound test would be enough.

But McAnsh isn't concerned about what this means for future cases — he'll simply present that additional information next time he goes to trial.

Bylaw may extend to all vehicles

City councillors are watching the legal challenges closely to determine whether they can extend the bylaw to include noisy cars and trucks.

Coun. Ben Henderson stands by the bylaw and says it has decreased noise levels in the city.

"A lot of people seemed to play ball and I've heard a lot of comments back from the folks that really were suffering, because they were getting that set of loud pipes going by at two or three in the morning, that it made a really big difference," he said.

The maximum decibel levels were set in consultation with the motorcycle industry.

Police use a sound meter to test noise levels. The meter is set up 50 centimetres away at a 45-degree angle from the motorcycle's exhaust system.

Officers take one reading when the driver idles the motorcycle, and another when the engine is revved to benchmarks of 2,000 and 5,000 revolutions per minute.

With files from the CBC's Tim Adams