DIY for Electronics

Understanding acoustics is not trivial because we can't see the sound waves. A simple propagation of waves in one or two dimensions can be explained using a hanging rope or throwing a stone in water, but phenomena like standing waves in 3D or phase relations are harder to explain. This article describes a little electronic gadget to visualize sound waves. It's called PhaseBrush because of its working principle. By moving (brushing) it around in the sound field, the LED colour will visualise the waves in real time. You can track the wave fronts or find the silent valleys. If you capture the brush motion with the changing colours in a long-time exposure you will obtain a 2D image of the acoustic as shown in the title image or the experiments presented below. All this can be done with a microphone and post-processing too, but in an incomparably boring and tedious way.

This article describes a microcontroller based digital door bell circuit that plays different sounds from an SD card. Instead of the boring "ding-dong" you can play your favourite song, a cool 303 acid sound, a Stephen Hawking phrase, a drum solo, animal sounds or what ever comes into your mind. The video above shows an example implementation of the digital door bell in a mask inspired by this guy.
While playing with the first prototype I noticed that having just one sound is quite boring and doesn't allow to distinguish visitors with their different ringing habits.