By means of an elongated, electrically conductive diaphgram (1,1A,1B) in a strongly magnetic field, a linear and an elongated sound source giving a high sound energy is obtained. At least two elongated diaphragms are in accordance with the invention positioned between intermediate and enclosing protracting magnet elements (2,2A,2B,4), whereby the transverse length (A) of the diaphragms are at least of the same size as that (B) of the intermediate protracting magnet elements. In this way, a sound without considerable interference merges at a short distance from the sources of the sound. By placing additional such sources of sound alongside each other, a broad sound source with a surface producing an essentially homogeneous sound field is achieved. |