Eight tuning forks that resonate at natural frequencies!
The equal tempered scale divides each octave range (frequency ratio of 2:1) into 12 half steps such that every two adjacent notes have equal frequency ratios. The ratio between any two adjacent notes on this scale is the twelfth root of two or about 1.06:1. An equal tempered scale consists of two whole steps (frequency ratio 1.12:1), a half-note (frequency ratio 1.06:1), three whole steps, and a half-step. The eight tuning forks resonate at natural frequencies that coincide with the frequencies of the natural notes on the equal tempered scale. Made of aluminum alloy.
These forks are recommended by the American Association of Physics Teachers and the Acoustical Society of America for teaching purposes. All are milled from bar stock, measure 1 x 2.5cm, and are tuned to an accuracy 0.5% at 20°C. Based on A=440cps.