John William Strutt, 3rd Baron Rayleigh OM (12 November 1842 – 30 June 1919) was an English physicist who, with William Ramsay, discovered the element argon, an achievement for which he earned the Nobel Prize for Physics in 1904. He also discovered the phenomenon now called Rayleigh scattering and predicted the existence of the surface waves now known as Rayleigh waves.
In 1873 his father, John Strutt, 2nd Baron Rayleigh died, and he inherited the Barony of Rayleigh.
He was the second Cavendish Professor of Physics at the University of Cambridge, following James Clerk Maxwell in this position from 1879 to 1884. He first described dynamic soaring by seabirds in 1883 in the British journal Nature.
Approximately 1900 Lord Rayleigh developed the Duplex (combination of two) Theory (Human sound localization using two binaural cues). Interaural time delay (ITD) and interaural level difference (ILD) (assuming a spherical head with no external pinnae). Humans perceive sound objects spatially, using the difference in the phase (time delay) of the sound and the difference in amplitude (level) between the two ears, in a similar way that stereoscopic sight provides depth perception. Also called two primary cues for azimuth (horizontal location) but possibly its two primary cues for a 3 dimensional bearing. For example when you hear a seagull call out you can determine roughly x y and z location of the sound. Although Pinnae reflections are considered a main cue for vertical localisation.