Singing too has evolved, and soprano singers reach their piercing high notes by precisely controlling the shape of their vocal tract to match its natural, resonant frequency with multiples of the one being produced by their vocal folds.

BBC: Helium-huffing gibbons 'sing with soprano technique'

Also concerning is the increasing magnitude and frequency of natural disasters.

WHITEHOUSE: The Changing Face of Veteran Reintegration

Ranger IV was also equipped with a seismometer and radio transmitter, designed to be released in a small capsule from the rocket before impact and land on the Moon in sufficiently good condition to measure the frequency of natural earthquakes in the body of the Moon.

BBC: 1962: First US rocket lands on Moon

RMS. As with modelling natural disasters, it is easier to assess severity than frequency.

ECONOMIST: Reinsurance risks

Risk models for natural catastrophes try to capture two things: severity (how hard a catastrophe might hit) and frequency (how often it might happen).

ECONOMIST: Reinsurance risks