Close. It's a 'spirometer'. This is exactly the point I was making in the first paragraph of my OP. None of us on this forum know what your mf and pp are so we have no real reference frame on which to base an answer. Now if you'd graphed out your apparent air flow (lung volume divided by note duration) against lung pressure through your comfortable pitch and dynamic ranges, we could start to gauge whether there's likely to be a lot of air mixed in with the buzz in some areas, or if you seem to be using excessive pressure to reach some notes, or if you haven't yet developed the skills to play a true pianissimo. If you have a good teacher, he would be able to determine this just by observing you while playing. We don't have that luxury, so we need good solid data if you are truly interested in an accurate comparison with the better players (not me yet, alas). One thing I have found is that if I'm sitting or standing in a comfortable position when I take my readings, I get figures that seem to line up fairly sensibly. But some readings have to be taken in a somewhat crouched position due to how my equipment is set up. This can easily wipe 20 seconds of my note duration. Tells me two things: 1) I need to recruit Mrs Seth's help to take the readings so I just concentrate on playing a relaxed steady note. 2) If there is any unnecessary tension in my body when I'm playing, it robs me of as much as half the air that I should be putting through the instrument. That is a BIG result.