This Beer Is Also a Musical Instrument
Chris Mufalli and Matt Braun have devised an instrument that you can drink in the form of Tuned Pale Ale. It’s not that the brew itself has any magical properties: Rather, the beer’s label is covered with a musical scale that lets you track what note will play when you blow over the bottle’s mouth.
Any bottle of liquid can function as a musical instrument, thanks to the phenomenon of Helmholtz resonance: When you blow over the mouth of the bottle, the air between the top of the bottle’s neck and the liquid below will vibrate in proportion to the pressure and bounce-back caused by the air being blown. UNSW:
The vibration here is due to the ‘springiness’ of air: when you compress it, its pressure increases and it tends to expand back to its original volume. Consider a ‘lump’ of air at the neck of the bottle (shaded in the middle diagrams and in the animation below). The air jet can force this lump of air a little way down the neck, thereby compressing the air inside. That pressure now drives the ‘lump’ of air out but, when it gets to its original position, its momentum takes it on outside the body a small distance. This rarifies the air inside the body, which then sucks the ‘lump’ of air back in. It can thus vibrate like a mass on a spring (diagram at right). The jet of air from your lips is capable of deflecting alternately into the bottle and outside, and that provides the power to keep the oscillation going.
Tuned Pale Ale is currently out of production following what Mufalli calls “great success” in its initial small microbrew batch: However, he’s currently looking for broader distribution options, so you may someday see it in stores yet. (Or you could just figure out your own height to note correspondences, but it might not look as pretty.)