How do earphones create sound waves that are longer than the size of earphones themselves?
In: Technology
The physics ELI5 is: it can do it because sound waves are [compression / “longitudinal” waves](https://www.youtube.com/watch?v=kxQj-wPePBU).
In other words – the speaker alternately pushes and pulls air along the direction in which the sound moves. Your ear responds to changes in pressure, and how frequently they arrive. The lower the frequency, the longer the wavelength. So the wavelength basically depends simply on how fast the speaker membrane vibrates – not on its size.
The Audio ELI5 is: almost certainly more complicated. Real audio engineering is complex – I don’t pretend to understand most of it – and there will be any number of other factors involved in the final design. Sound volume depends on how much energy goes into the wave, for example, and that’s related to, e.g., how much air the membrane moves as it vibrates – and a small membrane isn’t going to be able to move as much as a bigger one. So a small speaker vibrating slowly can produce a low note, but it’s also going to be a rather quiet one. But in principle the physics holds: there’s very little stopping a speaker of any size producing a note of any wavelength, beyond its physical ability to vibrate at the required speed.
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