Sand on some beaches and dunes emits a distinct 'squeaking' sound when moved under pressure.
It only affects certain types of sand - more rounded and drier grains generally don't squeak (as much).
The underlying acoustic mechanism as yet undiscovered.
“We can land a remote controlled robot on Mars but we don’t know why sand squeaks here on Earth and to be honest I kinda like that.”
A list of locations where squeaking sands can be found is maintained by the Acoustic Engineering dept. at the University of Salford, UK.