The electromechanical transducer (2) includes a rotor (4) and two coil (6, 8), the rotor being formed of first, second and third parts (10, 11, 12) made of magnetic material with respectively first, second and third superposed central zones (14, 15, 16), a first, axially polarized, bipolar magnet (18) being arranged between the first and second central zones and a second bipolar magnet (20) axially polarized in an opposite direction to that of the first magnet being arranged between the second and third central zones. The first and third parts each include N tongues, where N is a number greater than one (N>1), which extend radially from the central zone and the second part including 2N tongues, of which N first tongues are folded such that their respective end zones are arranged in a first geometrical plane (26) in which the tongues of said first part are located, and of which N second tongues are folded such that their respective end zones are arranged approximately in a second geometrical plane (28) in which the tongues of said third part are located. The N first tongues of the second part are located respectively opposite the N tongues of the third part whereas the N second tongues of said second part are located opposite the N tongues of the first part. The two coils are located between the first and second geometrical planes of the rotor such that, when the rotor is rotating, the end zones of the rotor tongues pass opposite said at least one coil.