(mathematical analysis) A study of the representation of functions or signals as the superposition of basic waves, involving the notions of harmonic functions, trigonometric series, Fourier series, Fourier transforms, almost periodic functions, and others.

An instrument used to measure the amplitudes, frequencies and phases of the components of a nonsinusoidal waveform; especially one used for analyzing audio frequencies.

(mathematics) A type of measure of central tendency calculated as the reciprocal of the mean of the reciprocals, ie, H=n/1/x_1+1/x_2+⋯+1/x_n

(mathematics) A function of two, three or n variables which is a solution to any of Laplace's equations

(mathematics) The solutions to Laplace's equation using spherical coordinates

(geology) A rhythmic shaking of the ground detectable by a seismograph, and associated with volcanic activity. Often a symptomatic warning of an eruption.

plural of harmonic engine

(historical) A machine in which the energy of an electric current is used, by means of two small electromagnets, to keep up the vibrations of a large and heavily-weighted tuning fork whose arms are connected to two pistons working a miniature pump.

plural of harmonic progression

(mathematics) A sequence of numbers whose reciprocals form an arithmetic progression.