Abstract: The present invention relates to an electro-acoustic transducer suitable for applications within mobile communication equipment and hearing aids. The transducer comprises two diaphragms positioned on opposite sides of a magnetic circuit having two magnetic gaps. When used as a microphone the transducer is substantially insensitive to vibrations, and when used as a speaker the transducer generates only very low vibration levels. The magnetic circuit has a number of advantages compared to conventional transducers with circular magnetic. The transducer can be made lightweight and with very compact dimensions compared to conventional designs. In a preferred embodiment the diaphragms are rectangular. The transducer may additionally be used as a vibration generator for silent alarm signals.

Abstract: An electroacoutic communications unit with a receiver transducer in a housing. The communications unit has accoustic connections both from the front side of the diaphragm of the transducer and from its rear side to the area inwardly of the face of the unit for engagement with a user's ear as well as to the area outwardly of this engagement face. These four acoustic connections constitute the four branches of an acoustic balance bridge with the transducer as a generator. This configuration is particularly expedient, as it is hereby possible to reduce the inner air volume in the communications unit behind the diaphragm of the transducer to a size which is without importance for the size of the telephone in practice. Furthermore, variations in the degree of tightness of the engagement of the communications unit with the user's ear will only influence the frequency characteristic to a very limited degree.