hello everyone,
for some time now, I have been deepening my knowledge of acoustic physics.
in particular, certain concepts (such as: standing waves) are indispensable to me for the construction of some musical instruments (using recycled materials), e.g., the tubaphone or the pan flute.
somethings like that, I came across some simple formulas useful for sizing sound tubes (of both types: open-open and open-closed). it seems to me that the physical quantities involved are: ambient TEMPERATURE (which affects the speed of sound propagation in the air); the LENGTH of the tube (and the resulting wavelength of the sound that can be produced); the FREQUENCY (generally considering the most common reference: 440Hz).
I have tested and verified practically on a PVC pipe how much is defined by mathematical formulas... (more or less) but I still have a doubt that haunts me:
the THICKNESS of the tube
the DIAMETER of the tube
do they have some impact on the sizing of the tube?
the doubt occurred to me during the practical verification.
my tube (open-open) measures precisely 77cm
performing some calculations, considering a speed of sound propagation equal to approx. 342 m/s, I come to the conclusion that such a tube, to produce an A sound at 220Hz, must be 77.73 cm long.
the sound actually produced by only 77 cm is very close to the real tuning (we are talking about quarter tones). mathematics would suggest that it is a quarter tone SHARP. but by striking it, the tube, in its current state, produces a sound intermediate between A (220Hz) and G# (previous), so, in reality, it is a quarter tone FLAT. therefore, to reach perfect tuning, I should decrease this measurement by ONLY a few millimeters, but I imagine that, in the field of musical acoustics, a magnitude of 5-6 millimeters is considerable.
as a final element, I add that my tube, in reality, is not perfectly cylindrical: one end is slightly wider than the other (generally many PVC tubes are molded this way to allow for the insertion of other tubes). it is nonetheless an enlargement (relative to the diameter) of 3-4 millimeters.
i hope I have been sufficiently clear
thanks to whoever can clarify my doubt.
good evening
ScalaQuaranta
