Next time please put the http in 😉 .

Upon passing 400/500 (I can never remember which one), climb power is automaticly selected, and either CLIMB, CLIMB1 or CLIMB2 becomes active. This usually causes the thrust to decline, and so the engine becomes derated.

I’m not sure about the sound, but maybe if the takeoff itself was derated, and it was a high speed climb out (high cost index), the change in thrust may not have been so significant. But the change in sound on this occasion of probably just caused by the microphone on the videographers camera.

I’m not a commercial pilot though, I don’t think we have any 777 pilots about, but i’m sure someone else will be able to help you.

Sam

Thanks for that Sam.

As stated in the original post I wasn’t sure if YT links were allowed or not so I left the http bit out.