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Making a rickroll laser: A parametric speaker
.(Electronics) Most speakers emit sound in all directions because they are relatively small compared to the wavelength. Audible sounds have wavelengths of up to several meters, so an acoustically “large” speaker might not even fit in your house.
The transducer’s capacitance varies by an order of magnitude between different frequencies, so unless you have a LCR meter, its best to experimentally find the value that produces the highest AC voltage across the array. Shorter wavelengths need less time delay to cancel out, so the same size speaker will be more directional at higher frequencies. With waves coming from just a two points, there are lots of other spots where they will coincidentally line up, but with enough sources that won’t happen anywhere except directly in front of it.
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