A 500 ml and 150 ml beaker make clinks that sound to my ears to be a perfect fifth. The wavelength ratio for a fifth is 2:3. The volume ratio of these two beakers is 3:10. To get a 1-dimensional ratio, we take the cube root, which is 0.6694, which is close to 2:3, hence the fifth.
I've been thinking about this for a couple days and finally had to do the math.