Also, as a nit: most of the sound from a typical gunshot comes from the bullet “uncorking” from the barrel and suddenly releasing the trapped high-pressure gase

Also, as a nit: most of the sound from a typical gunshot comes from the bullet “uncorking” from the barrel and suddenly releasing the trapped high-pressure gases all at once, generating a shockwave. This is precisely why suppressors (“silencers”) work, they slow down and cool off these gases before releasing them. The supersonic crack is a factor, but it’s usually not most of the sound. Typically you will not be able tell a difference between subsonic and supersonic ammunition in the same caliber, it’s all too loud to notice. It’s only once it’s suppressed that you can tell. Many common handgun calibers are naturally subsonic too, such as the fairly popular .45ACP, as well as heavier 9mm loads. The march 22lr ammo I use is naturally subsonic (faster, trans sonic ammo is less accurate), and it’ll still destroy your hearing without ear protection on.