Looking to quiet the air sound in the tubing when breathing in

[ragtopcircus]

I hear the air in either a 12mm or 15mm hose, but each has a different character. It's not loud at all, but I hear it more clearly with my quieter machine. 12mm is really too small IMHO, but even stepping up to 19mm (if your machine supports that) may change the sound enough to make it less noticeable.

Also, changing the length may help, even for the same size tubing, by shifting the resonance(s) to a different frequency range.

[Ewerning]

If you are talking about the sound of air traveling in the tube and mask, a bigger hose diameter (22mm) will produce less noise because the air has less velocity inside it. At the mask try choosing a mask that has less curves and restrains for the air flow. And check the air leaking from the mask. Sometimes smaller vents cause more noise.