Die Akustik was written by Ernst Chladni in 1801, and is the first comprehensive work on acoustics to appear in German. The first part dealt with the general theory of tones and the arithmetic part of acoustics, consonance and dissonance, musical intervals, the number of vibrations per second for pitches and equal and unequal temperaments. The second part, reviews the properties of vibrations of resonating bodies previously researched by Bernoulli, Riccati and Euler. The third part deals with the propagation of sound through fluids and rigid bodies. The fourth and final section, explanatory and experimental, reviews the physiology of the ear in humans and animals.