Deep-drawn membranes formed of polyester or polycarbonate films, comprising units of Formula (I) and (II), useful for acoustic signal converters as microphones and speakers. The film can be produced by thermoplastic processes or solvent cast processes. Especially suitable for the production of small membranes with a diameter of up to 10 cm useful in mobile devices as microphones, mobile telephones, laptops, personal digital assistants (PDAs), headphones or as signal transmitters