German physicist who discovered the Barkhausen effect, a principle concerning changes in the magnetic properties of metal.

Barkhausen attended the universities of Munich and Berlin before earning his doctorate in 1907 from Göttingen. After working for the Siemens & Halske laboratories in Berlin, he accepted the world's first professorship in the communications branch of electrical engineering, at the Technical Academy in Dresden (1911). There he worked on theories of spontaneous oscillation and nonlinear switching elements and formulated electron-tube coefficients that are still in use. He also experimented with acoustics, proposing methods for the subjective measurement of loudness.

His work in acoustics and magnetism led to the discovery in 1919 of the Barkhausen effect, which provided evidence that magnetization affects whole domains of a ferromagnetic material, rather than individual atoms alone.

In 1920 Barkhausen developed, with Karl Kurz, the Barkhausen-Kurz oscillator for ultrahigh frequencies (a forerunner of the microwave tube), which led to the understanding of the principle of velocity modulation. He is also known for experiments on shortwave radio transmissions.