I get that going at the speed of sound creates sonic a sonic boom. But what happens when the object is close to that speed, but not there yet? Say at 1200 kmph.
Is the sound louder with the size? If so, how loud?
For example, how different would a bullet, a baseball, and a bowling ball, going at the same speed sound?
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Subsonic object make noise primarily from turbulent flow around and behind them. the object can shed vortices on alternate sides, forming a “vortex street”. (You can see this easily by putting a stick into flowing water.) The alternation produces low frequency sounds, while collapse of the vortices produces a broader spectrum. Turbulence where the boundary layer separates and recirculates is noisy.
In general you cannot compute this. Many practical studies have been done. For instance, NASA Ames had a program devoted to listening to helicopter rotors in flight, and testing new designs. Search on “Rotor Systems Research Aircraft RSRA” and “Quiet Shorthaul Research Aircraft QSRA”.
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