(under subclass 175) Subject matter wherein the means for modifying the sound includes modulating the sound by interacting or introducing an additional higher or lower frequency to the sound source, the resulting sound being at a different frequency.
SEE OR SEARCH CLASS
333, Wave Transmission Lines and Networks,
165+, for electrical wave filters, and particularly subclasses 186+ for electric wave filters of the electromechanical transducer type, and subclass 81 for electrical attenuators.
