Sound hole

[1][2] One of the conclusions of this paper was that acoustic conductance (air flow) is proportional to the length of the perimeter of the sound hole and not the area.

They proved this mathematically, and showed how it drove the evolution of shape of the F-holes in the violin family.

The highest air flow in a violin's F-hole are the places at the top and bottom where the points nearly touch the other side.

The effect is analogous to putting one's thumb over the end of a hose to accelerate the water coming out.

[3] A few hollowbody or semi-hollow electric guitars, such as the Fender Telecaster Thinline and the Gibson ES-120T, have one f-hole instead of two, usually on the bass side.

The sound holes of cellos and other instruments of the violin family are known as F-holes and are located on opposing sides of the bridge .