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.

plural of harmonic mean