Sound Horn, Passive Amplifier

Описание: Inspired by my wife's art class, where they used a drinking glass as a passive amplifier, I decided to create my own sound horn. My first attempt involved using an oak log from the firewood pile, but it didn't have the diameter I needed for the correct shape. To design the horn, I used the formula below to calculate the flare constant and a second formula to determine the internal area at 20mm intervals along the horn's length. Using the area the internal diameter (d) can be calculated using the formula below.

This project turned out to be a fascinating experience. The final horn measures 170mm in length (original design: 160mm), with an output aperture of 157mm (design: 150mm) and a starting diameter of 50mm, matching the intended design. The phone pocket is 135mm tall, 110mm wide, and 45mm deep. Initially, I planned for the pocket to be circular, so the horn could double as a tall vase when not in use, but this would have required a very large pocket and, visually, seemed awkward. The square pocket ultimately made the device more stable.

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Flare Constant
m =(ln(St/S0))/l
m = flare constant, St = end area, S0 = start area, l = length of horn, ln natural logarithm

Area at set distances along length
Sx = S0.e^mx
Sx = area of horn at x from the start, S0 = start area, e =2.718 Euler's number (approx 2.718), m = flare constant, x = distance along the horn from the start.

Diameter set distances along length
d=2.√(Sx/π)