# Barometric music

Sound is the way we perceive rapid fluctuations in air pressure. The lowest notes humans can hear are around 20 Hz — that is, when the pressure fluctuates up, down, and back to normal 20 times per second —, and the highest notes around 20,000 Hz, though the exact range varies with age, and from person to person.

One of the tools used for tracking and predicting weather is the barometer, which measures the ambient pressure of the atmosphere around it, which fluctuates. Unlike pressure associated with sound, these fluctations are very gradual; I’m no expert, but my vague impression is that each cycle — from, say, the peak of one high to the peak of the next — takes about a week, rather than a day or a month (at least here in New Zealand).

But what if we sped it up? Doubling the speed of the pressure fluctuations corresponds to raising the pitch by an octave. If we doubled the speed 27 times, raising the pitch by 27 octaves, something that happened every week would then happen just over 220 times per second; 220 Hz is the A just below middle C.

But we’d need quite a few samples of air pressure. For CD quality, 44,100 samples per second of audio are required. If we were doubling the speed 27 times, we’d need just over 1.18 samples of air pressure per hour, on average, to get a sample rate of 44.1 kHz in the final audio. One sample per hour might be adequate, but we’d lose anything that might be there to be heard in the highest pitches of the human hearing range.

And then there’s the length of the final audio. Each second of the final audio would require about 4 years and 3 months of barometric data.

It’s not inconceivable that some weather stations around the world have been collecting barometric data at least every hour for several years, and have put all the data online for easy downloadability. I haven’t done a thorough search yet, but some of you might be able to give me tips about where to find such data.

Finally, there’s the question I’m really interested in: What would it sound like? My guess is that it would sound like white noise, at least in the layman’s sense of the term, but there’s a chance that I’m wrong, and that the weather in some parts of the world might be regular enough for a discernable pitch to be heard. And I wonder if certain weather patterns, like El Niño and La Niña, would sound discernably different.