All the engines come with mufflers. The mfgs usually design the muffler to detract from the power as little as possible. Because of that, they almost always wind up with mufflers that produce the sound level that is the present standard. In other words, they all will wind up rating about the same db's on a meter.

The 4strokes all turn about the same rpm's. That is quite a bit slower than most 2strokes. Since the slower turning props make less noise, and prop noise is a considerable portion of the total noise, the 4strokes sound different and most people interpret that as quieter.

It's also impossible to categorize the noise level of "a 60" or "a 46" since there are dozens of each and some are simply louder than others in their own size, so there really is no answer. Other than that most are made to sound no louder than the current standard.