In reading an answer here: How close can I get to a rocket launch and not get killed?, the comment is made that noise from the launch can be tremendous. This isn't a big surprise to anyone who's watched a launch on video, or especially has had the privilege of watching one live. So, fundamentally, why are rocket launches so loud? What components of a rocket motor firing contribute to the tremendous noise? I understand that a tremendous amount of energy is being expended in a very short timeframe and concentrated area (rocket nozzle).
This article indicates that a typical nozzle velocity is 2802 m/s, which is around Mach 8. I'm sure the shock wave of that nozzle velocity (and the 2.8 km/sec escape exhaust velocity) is a significant contributor to the noise, but are there other significant contributors to launch noise?