I commute by Canada Line into work.

I bypass downtown traffic in exactly 20 minutes, while getting to feel smugly virtuous for taking public transit. One problem:

The Canada Line has become physically painful to ride.

Anywhere along its underground route it is unusually noisy, at least compared to any other subway I have ridden. (The exception along the route: The quiet bridged portion spanning the Fraser River.)

But on the curved underground portions of the line, the interior cabin noise is positively painful — it’s a prolonged, high screeching which might last 10 to 20 seconds and makes any kind of communication impossible.

So I wondered: Was the Canada Line noise loud enough to affect hearing?

On May 20, I emailed questions to TransLink media relations. What caused the screeching? Had the train’s interior noise had been measured? If so, what was the highest reading? Had there been any complaints?

Three days later — so much for deadlines — TransLink responded. In the matter of noise complaints, the email read, there had been five in 2012, two in 2013 and none in 2014 (except for mine). As for the other questions:

“As the Operator and Maintainer of the Canada Line, PROTRANS BC Ltd. (the private operator of the Canada Line) is required to regularly monitor the level of interior and exterior train noise and respond accordingly to ensure that levels are within permissible limits. Like many other rail transit systems, the Canada Line trains operate ‘steel on steel’ (wheels on rail) and the contact point between the two areas emits different noise levels at different locations throughout the network. These noise levels are also affected by the natural wear on the wheels and rails that occurs ... To maintain compliance PROTRANS BC Ltd. regularly performs maintenance to re-profile the train wheels and track. The described ‘screeching’ noises in the tunnel are in locations where the trains pass through some of the tighter geometry curves. PROTRANS BC Ltd. is currently targeting these areas thru re-profiling of rails and installing additional rail lubricators.”

That was it. No mention of decibel levels being measured, or what constituted noise levels “within permissible limits.”

I phoned TransLink media relations that day and asked again if the train had been measured for sound levels. If so, what were the permissible limits, and were those levels ever high enough to be considered harmful to hearing?

Five days passed without an answer. On May 28, I emailed again, asking if there would be any reply. There was no reply.

Another week passed. Finally, on June 4, TransLink media relations responded.

“Here’s a response from PROTRANS BC,” the email began.

“Contractually PROTRANS BC Ltd. are required to measure interior train car noise only on the elevated Guideway segments. However, for planning of track maintenance they measure this throughout the whole of the line. The results of the last noise measurements that were taken on the 1st May 2014 are as follows:

“Internal Train noise: Elevated Guideway.

“Average Segment Leq = 67dBA