The idea must have started on loudspeaker membranes being able to move as a whole by printing the electron conductor on the insulating thin film. By reciprocity a microphone is created. The idea is that the membrane moves as a whole and producing an electrical wave as a whole.
The magnetic field is arranged by opposite facing magnets (the membrane in between) so that lines of force run parallel to the membrane. The magnetic field lines must be perpendicular to the moving conductor by sound waves.
The magnetic field reverses mid way so the direction of the printed coil must reverse too. So in fact the coil shape is made up of many U shaped conductors one inside the other and all connected in series. There are additional conductive parts etched, rather printed , on the insulating membrane whose use is only balancing the membrane weight symmetry symemtry so that it moves as a whole. And perhaps also electrical damping as there are currents developed in them as well although they are not connected to the series coil arrangement.
See patent US3922503 by Shunichi Tabuchi, Fostex.
The shape of the coil is very unusual:
https://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&II=1&ND=3&adjacent=true&locale=en_EP&FT=D&date=19751125&CC=US&NR=3922503A&KC=A
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