QM2 Whistle Observation

I have a random question after watching several videos of QM2. Does anyone know why sometimes it sounds like QM2 is sounding just one whistle (It sounds like just the original QM whistle) yet other times it sounds like both whistles are sounding. I'm not talking about the daily whistle tests, I'm talking about various departures, like in the videos below.

One whistle:

Two whistles:

Are my ears playing tricks on me?

No, your ears are not playing tricks. The whistles are operated separately.

The starboard side whistle is from the original Queen Mary. It was rebuilt to operate on air and sounds a low Ab. It is on "permanent loan" and presumably would be returned to that ship when QM2's service days eventually end.

The port whistle was new for the ship and sounds a low C, which is the lowest pitch now allowed by the US Coast Guard.

And here is a photo of the starboard whistle on RMS Queen Mary 2 (from RMS Queen Mary) blowing steam whilst announcing her departure during a cruise in 2007.

www.flickr.com/photos/pepperrn/4644813863/in/album-72157623936815195/

The added steam effect (the whistles are of course air-operated as BlueRiband states) stopped working some time ago sadly... luckily I got to see it on a few occasions. Wish it still worked now!