The shape is twice as efficient at transmitting sound as a round hole researchers found.

MIT accoustics expert Nicholas Makris studied the development of the holes. he found that the the more elongated the sound hole, the more sound can escape from the violin, and set about to prove it mathematically.

He says that, while it is unclear whether the instrument makers understood the mathematics behind the efficiency of the f-hole, it developed in an “evolutionary” way.

He and his team analysed 470 instruments made between 1560 and 1750 and found that the change from round hole to the f-hole was gradual but consistent.

Whatever they knew about the maths, instrument makers “definitely knew what was a better instrument to replicate,” says Makris.

As Jennifer Chu writes in MIT News:

The more elongated these are, the more sound a violin can produce. What’s more, an elongated sound hole takes up little space on the violin, while still producing a full sound — a design that the researchers found to be more power-efficient than the rounder sound holes of the violin’s ancestors, such as medieval fiddles, lyres, and rebecs.

Makris didn’t set out to study violin acoustics, Chu reports, but arose when he took up a new hobby – playing the lute.

“I’m an acoustics expert, but promised myself I wouldn’t think about the acoustics of the instrument, I’m just going to play the thing,” Makris told Chu.

That thinking didn’t last long, as he began trying to understand his instrument better.