Deserts across the world have been found to sing in two different styles. Depending on conditions of heat and pressure deserts can emit sounds that sound like a loud boom or a short and rapid fit of burping. Melany Hunt, a professor of mechanical engineering at the California Institute of Technology, Nathalie M. Vriend, a doctoral student at Caltech, and Rob Clayton, a professor of geophysics at the University of Cambridge, are the first to determine the acoustic physics that makes deserts sing.
Both types of sounds that deserts make combine the same types of acoustic waves. The difference in the sounds that are produced is the predominance of one type of wave over the other. A surface Rayleigh wave, traveling radially along the surface of a dune in a nonlinear manner, is primarily responsible for the burping sounds. Linear P-waves that travel through the volume of a dune and are reflected from the internal layers of the dune are primarily responsible for the loud booming sounds. All deserts sing in a range between 70 Hertz and 110 Hertz.
The researchers also found that each individual dune has a natural resonance that produces an individualized frequency of sound that is dependent on the shape of the dune and the shape of the grains of sand composing the dune. This is the first evidence ever found that shows the grains of sand are involved in the sounds that deserts make because the amplitudes of the sound waves are on the same order of size as the grains of sand. The researchers used modified geophones to measure seismic vibrations because the equipment operates within the range of the acoustic vibrations.
