I was looking at stethoscopes on-line, and some are offered in both 22" and 27" lengths. I have heard that the shorter the tube, the better the sound quality. Is there a big difference between a 22" and a 27" stethoscope as far as sound quality goes? I am slightly hard of hearing, so sound quality is a big issue with me, however, I don't need anything as extreme as an electronic stethoscope. I will be working in PICU, so I want a good quality scope. Any recommendations? Thanks!