So sound is caused by something vibrating. Any sound that's coming from the boosters vibrating air molecules outside which vibrate the windows which vibrate the air inside would fade out to nothing as air outside got thinner. But any sound coming from the boosters vibrating the vessel itself would still be heard even as the vessel got completely out of the atmosphere.

If engines are firing or mechanical parts are moving they will likely cause vibrations that will travel through physical connections so you will hear them. But if nothing on the ship is moving or creating noise then there is no ambient sound and you would likely start to become very keenly aware of the noises your body makes. They build perfectly sound proof rooms here and apparently from people who have stayed inside you stsrt noticing your saliva squishing around, the dull thump of your heart beating, gurgles from your stomach and gut etc.

The sound rom the engines should I think not change from the time the vehicle goes supersonic up to engine cutoff, since from that point on, the only sound from the engines that can reach the crew is that which is transmitted through the vehicle structure.

Aerodynamic noise from the air flowing around the vehicle (though I don't know how audible that would be with the smooth aerodynamics around an ascending rocket) would of course steadily dimish during ascent.