Diodes sound like...

this (MPEG file). It’s the closest audio representation of the quantum avalanche effect that we could make. A Zener diode was sampled at 50kSa/s using an 8 bit oscilloscope. That data was then converted to an unsigned 8 bit PCM file with no volume changes whatsoever. The only change we were forced to make was to marginally down sample to a standard 44kHz when exporting the data as mp3.

The Zener avalanche effect as a raw soundwave with a linear scale.

Raw soundwave with a linear scale.

Notice the close similarity with the original oscilloscope trace halfway down this page. Also notice the virtually white noise spectrogram below. Although forced resampling to 44kHz will have reduced the bandwidth to somewhat less than 22kHz.

The Zener avalanche effect as an audio spectrogram.

Audio spectrogram.

Looking to broader frequencies, the Fourier transform below shows a (kinda) flattish range out to 500kHz, as measured by oscilloscope. There is also a great deal of quantization noise as these are 8 bit integer samples of random sawtooth forms. Just the signal-to-quantization-noise raises the noise floor to well above -48dB. Fortunately for us, quantization noise is truly random and so adds sauce to the goose (additional entropy).

Fourier transform of a Zener avalanche signal sampled by oscilloscope.

Fourier transform of the avalanche signal sampled by oscilloscope.