This paper presents a study of the noise in three-phase two-speed cage rotor, totally enclosed externally cooled induction motors. Investigations include two-speed threephase induction motors with Dahlander winding connection or separate windings, with rated speeds of 3000/1500, 1500/750, 1500/1000 r.p.m. The investigated motors, manufactured by S.C. Electroprecizia S.A. were placed in a semi-anechoic chamber in order to determine the noise-to-frequency characteristics (spectrograms). This paper is based on the results and conclusions obtained after analyzing these noise spectrograms.

Keywords: Noise, Induction machine.