As much static and interference as we hear on the tape the sound of somebody whistling is clear as a bell. I assume they were whistling almost straight into the microphone because it was mounted at the handlebars above the gas tank. Can we safely assume that the Whistler was the person with their mic keyed?
When officer McClain and the dispatcher heard that whistle they both came to the conclusion that the person with their mic stuck was a different officer riding a 45 cubic inch trike. I find it compelling that McClain said he was definitely not a whistle while you work kind of guy. He actually seemed to be sort of gruff. I think people know if they whistle or not.
McClain and the dispatcher we're also convinced that the sound of the motorcycle was the classic sound of a 45 cubic inch three wheeler like the meter maids Drive. I owned a 66 CHP bike and so I know the sound of a 74 cubic inch Harley intimately. I have to agree with McLain and the dispatcher that's the sound of the engine is very distinctly not a 74 cubic inch Harley. Although the engine sound is mostly a static reproduction of the engine you can still count the RPMs when you graph the sound. To me it is running at higher RPM then McClain would have been doing. I think I got it at about 2300 RPM just a couple seconds before the head shot. McLane said he had come to a complete stop when he looked to left and saw the headshot. I find his testimony compelling and I think I hear what he heard on the tape. His opinion has really kept me from going down the rabbit hole on this issue.
I never met Officer McLain so I don’t know if he was a whistler or not. But can be assumed that no one riding a motorcycle at high speed, catching up to or escorting the speeding Presidential limousine, on its way to Parkland, would be whistling a merry tune.
However, it is easy to imagine, an officer who is casually waiting for the President’s arrival at the Trade Mart Center, and has no idea that the President has been shot, might be casually whistling. And, indeed, after we hear the “Attention all units”, likely the Dallas County Sheriff’s announcement of the shooting at Dealey Plaza, we hear no more whistling.