As mentioned in the article there are a lot of common watch crystals that oscillate at 32.768 kHz, but they are tuning fork crystals rather than bulk mode (or modern SAW), which have much higher frequencies. It would be challenging to lower the frequency of these, but perhaps you could evaporate Au or W onto the tips and reseal them to get into the audible frequencies. Much easier would be to get two crystals which beat against each other in the audio range. Even a couple of 6MHz crystals 100ppm off would be ~6kHz (temp sensitive), and you would need some driving circuits, but you might be able to hear the beat by driving an electret microphone or a really tiny tweeter coil speaker (probably need an amp though).

It's much easier to build/buy electrical rather than mechanical LC components to hit audio frequencies ~100Hz-10kHz.

You can get quartz to resonate down to upper audio frequencies with certain crystal cuts and manufacturing techniques but it's difficult. Typically, the lowest frequency in common use is with its use in watches with a frequency of 32,768Hz (that's about the lower limit where manufacturing and frequency combine to make a useful product).

For electronic circuits such as frequency reference markers where frequency stability is important the lowest practical frequency is 100kHz with 1Mhz preferred, and where frequency tolerances are tight 5 and 10MHz are much preferred with operation in a temperature stabilized oven to minimize frequency drift.

The most frequency-stable crystal cuts are at those frequencies, as frequencies increase (say >10MHz to 100MHz), which at the highest frequencies require the crystal to operate in overtone mode, frequency stability again tends to decrease.

There are piezo buzzers and beepers, of course.