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Celebrating the birthday of Lord Rayleigh: A ‘major influencer’ in Acoustics

William Strutt was an English physicist living between 18th and 19th centuries. His full name was John William Strutt, 3rd Baron Rayleigh of Terling Place.  He was born in Maldon, Essex on November 12, 1842 and died in Terling Place, Essex on June 30, 1919.

This English scientist and Physics Nobel prize winner (1904) made fundamental discoveries in the fields of acoustics and optics and is often considered to be a ‘major influencer’ in acoustics.

As Lord Rayleigh’s birthday approaches, we explore briefly his work and enduring contribution.

Lord Rayleigh attended Eton College at the age of ten. Due to continued ill health, his parents thought a home education would be more appropriate.  After completing his early education, in 1861 Lord Rayleigh began a course in mathematics at Trinity College in Cambridge, which proved vital to his understanding of physics. Lord Rayleigh later spent five years as the second Cavendish Professor of Physics at Cambridge where he research of optics and vibrations. The academic began investigating hydrodynamics, wave theory, electrodynamics, viscosity, photography and electrodynamics. He created a radical new way of carrying out physics experiments at Cambridge and was responsible for increasing the number of students studying physics at the college from six to seventy.

The Theory of Sound

Whilst his initial work was primarily mathematics-focused, researching optics and vibrations, his later work covered a broader range as he investigated wave theory, sound and colour vision.

Lord Rayleigh became known for his notoriously patient and delicate experiments and being an excellent instructor.

In 1894, Lord Rayleigh’s two-volume book ‘The Theory of Sound’ was published. This major text is still being referred to by acoustic engineers today. It focuses in the first instance on the mechanics of a vibrating medium which produces sound whilst the second part looks more closely at acoustic wave propagation.

In his book, The Theory of Sound, Lord Rayleigh discovered  (put very simply) that if a sound is travelling from a far distance then the intensity of the sound is different than if you hear it from a closer distance.

The Duplex Theory

Around 1900, Lord Rayleigh researched further into the human auditory system and developed the duplex theory of human sound localisation.  This demonstrates that the brain relies heavily on ITDs (interaural time difference) for low frequency sounds, and on ILDs (interaural level difference) for high frequency sounds.

Lord Rayleigh’s legacy

The accuracy of Rayleigh’s experiments and the quality of his work eventually won him a Nobel Prize for Physics.  His pioneering two-volume book The Theory of Sound essentially clarified the mechanics of vibration and acoustic wave propagation, an accomplishment that has meant that Lord Rayleigh is considered a ‘major influencer’ in acoustics and why his birthday is still celebrated more than 170 years after his death.  A lecture in 2014 by Professor Davis who has been working with the present Lord Rayleigh – the Third Baron’s great-grandson – on preserving and promoting the laboratories used by his forebears and taken from the NPL website can be viewed here for additional information.

If you enjoyed this blog, make sure you revisit our blog regularly for more information about more important dates and figures from the world of sound and acoustics.

 

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