A speaker apparatus which can remove undesirable vibrations and can produce sounds of excellent quality of acoustic signals having high audio frequencies is presented by increasing a strength of a flat joint portion and by properly setting a mass ratio between a central dome-like diaphragm and an edge-like diaphragm of a speaker diaphragm. This speaker apparatus includes a diaphragm portion in which a mass ratio of the edge-like diaphragm relative to the dome-like diaphragm falls within a predetermined range near 1 and a fixed portion at which a bobbin of a voice coil or an end face of a conductive one turn ring is bonded to and fixed to a flat portion for joining the dome-like diaphragm and the edge-like diaphragm so that mechanical strength of a joint flat portion of the diaphragms can be increased.

An electrodynamic transducer has a diaphragm substantially having two parts with different profiles, namely an acoustically active central part and an annular part laterally adjoining the central part and serving for the resilient suspension of the diaphragm in its entirety. A narrow coil seat for a wire coil of the transducer is located between the central part and the annular part. For the purpose of developing a compact yet electrodynamically sensitive acoustic transducer, the annular part is not arranged radially outside the central part of the diaphragm, but is shifted inward according to the invention. The curved annular part is thus accommodated under the axial curvature of the central part. The annular part can therefore have the annular width required for an ideal resilient suspension without negatively affecting the outer dimensions of the transducer.

For musical instruments or sound reproduction, finer sound definition is preferable. In sound reproduction, electro-acoustic transducers fitted with round membranes or electrostatic system stripes are common. No system states that the sound created is correct for the human ear. The present method concerns a fractal shape responding to criteria of the human ear shape. A membrane which, like the ear via its shape, is a set of resonators with different frequencies. The membrane shape, known as a harmony amplifier, has independent tongues emitting from a given surface, like fingers of a hand coming out of the palm. A membrane can be put into digital form by tongues. The membrane is placed in a musical instrument. Another variant is a membrane mounted on a sound frequency generator constituting an electro-acoustic transducer. This is effective for all types of musical instruments and particularly for audio and audio-visual applications.

According to the state of the art, insofar as the respective components of the loudspeaker cannot be built in one piece, the respective components of the loudspeaker are joined to each other by adhesives. For example, it is known to bond the aluminum voice coil support (10) to the paper loudspeaker diaphragm (11). However, if loudspeakers with such bonded joints must operate above 120 degrees Celsius, no long-term continuous operation of the mechanically highly stressed adhesion can be expected. The invention therefore has the task of presenting a very strong mechanical joint of the loudspeaker components. The task is fulfilled according to the invention, in that at least the surface areas (13.1, 13.2) of the loudspeaker components to be joined to each other [perhaps the voice coil support (10) and the loudspeaker diaphragm (11)] are made of metals that can be ultrasonically welded to each other, and that the joint between the two components of the loudspeaker is ultrasonically weldable. Insofar as required, an insulation arrangement (16) can be placed between the two just mentioned loudspeaker components, which can be ultrasonically welded to the respective components of the loudspeaker [in this instance loudspeaker diaphragm (11) and voice coil support (10)], through their metal coatings (19.1, 19.2), which are also made of ultrasonically weldable metal.

An implantable medical device includes an acoustic transducer for intra-body communication with another medical device via an acoustic couple. The acoustic transducer includes one or more piezoelectric transducers. In one embodiment, an implantable medical device housing contains a cardiac rhythm management (CRM) device and an acoustic communication circuit. The acoustic transducer is electrically connected to the acoustic communication circuit to function as an acoustic coupler and physically fastened to a wall of the implantable housing, directly or via a supporting structure.