History of acoustics

Early research in acoustics

The fundamental and the first 6 overtones of a vibrating string. The earliest records of the study of this phenomenon are attributed to Ancient Chinese 3000 BC.Many books and websites about musical theory written by Western musicologists mention Pythagoras as the first person studying the relation of string lengths to consonance. However, from at least 3000 BC, the Chinese were already using a scale based on the knotted positions of overtones that indicated the consonant pitches related to the open string, present at their Guqin. Like the Chinese, Pythagoras wanted to know why some intervals seemed more beautiful than others, and he found answers in terms of numerical ratios representing the harmonic overtone series on a string. Aristotle (384-322 BC) understood that sound consisted of contractions and expansions of the air "falling upon and striking the air which is next to it...", a very good expression of the nature of wave motion. In about 20 BC, the Roman architect and engineer Vitruvius wrote a treatise on the acoustical properties of theatres including discussion of interference, echoes, and reverberation—the beginnings of architectural acoustics.

The physical understanding of acoustical processes advanced rapidly during and after the Scientific Revolution. Galileo (1564–1642) and Mersenne (1588–1648) independently discovered the complete laws of vibrating strings (completing what Pythagoras had started 2000 years earlier). Galileo wrote "Waves are produced by the vibrations of a sonorous body, which spread through the air, bringing to the tympanum of the ear a stimulus which the mind interprets as sound", a remarkable statement that points to the beginnings of physiological and psychological acoustics. Experimental measurements of the speed of sound in air were carried out successfully between 1630 and 1680 by a number of investigators, prominently Mersenne. Meanwhile Newton (1642–1727) derived the relationship for wave velocity in solids, a cornerstone of physical acoustics (Principia, 1687).