+1 BB
Open draw for me, though not dogmatically
As for the sound test, I believe the high frequency pitch would be due to the sharp edges, sharp turns or obstacles in the airway, where the airflow hit something violently, the higher possibilities that turbulence would occur and the steam would more likely to condense as water. This would cause wet smoking, poor draw, tongue bite and other down sides. The width of the air hole is not the decisive factor. However, for the same amount of draw, a tighter air hole would certainly speed up the airflow which for sure tends to faciliate turbulence. Thus open up the draw would solve the problem somehow. I guess it is an usual case that no one could always keep an good rhythm during a bowl. One would more or less make heavy or frequent draws, pack or tamp the tobacco a bit tight. Open airway makes the pipe more "tolerant" in those situations. And so comes the open draw theory. Actually the smooth build of the transition of the air way is the most important thing. Mr. Newcombe also mentioned this in his book. It was a conversation with Jess if my memory is correct.
I have modified most of my pipes. I believe there is a best air hole width if all other factors would matter are determined, for instance the shape and the chamber of the pipe, the smoker, the tobacco and so on. And there is also an optimized range of the width of the air hole, which would fit most regular smokers, regular blends ... If I can make sure the size of the air hole not in this range I would certainly change it (it is a good thing that they are MY pipes so the range would be narrowed down to my personal puff rhythm and my favourite blends). I have opened most of my pipes and the results were satisfying with no exception. I got a small group 2 dunhill tanshell billiard from the 50s with a air hole width of 3.6mm. It smoked tight and wet with lots of tongue bites. I opened it to 4mm but nothing changed significantly. I moved to the next step, 4.2mm and all a sudden it smoked like a different pipe! I got another dunhill half bent apple (shape No. 4113) smoked not as good as I expected. The problem was the air hole in shank did not fully face the air hole in tenon, I had to turn the PC to get it from the bit into the chamber. I worked with a cuspidal file on both the upper side of the air hole in tenon and the lower side of that in shank so the two openings met each other better and a PC might go through with no resistance. The pipe became one of my everyday pipes, although the air hole openings became oval. I have a group 5 billiard with an air hole of only 3.5mm, but it smokes so smooth and nothing requires any modification.
Some more on the climates. It was damn dry and full of air pollution in Beijing, especially during the winter. So I got a Venta air cleaner with moisturizing function. The average humidity of my room rose from 30% to 50 - 60%. After a few days, I got terrible smokes and tuns of tongue bites. I put my pipes on scale and found they were 0.2g - 0.5g heavier than before (as a former scientist I keep the hobby to quantify things. And I wipe out almost evrything after each smoke to maintain a very thin cake, thus the weight change of cake would be negligible.). Please note that my pipe usually gains 0.05 - 0.1g after a regular smoke. In another word they were carrying the moisture of a few smokes. I knew it was the humid air that prevented the pipes from fully recover. Then I found a drying case (usually used for photographic gears) for them and everything went back to normal.
After all, I am still a newbie of pipe smoking but hope this may help a little bit.
