Where information is to be conveyed as acoustic waves, embodiments of the present invention provide a transmitter capable of causing acoustic waves that convey information to be not easily perceived by the human ear. A transmitter, being an apparatus that converts various types of encoded information into acoustic wave(s) in the audible spectrum and carries out transmission thereof, comprises microphone(s) that cause ambient sound(s) from location(s) at which acoustic wave(s) is/are transmitted to be input as ambient sound signal(s); peak frequency detector(s) that detect, within ambient sound signal(s), peak frequency or frequencies of major constituent(s) of ambient sound(s); carrier wave generator(s) that generate carrier waves at a plurality of frequencies that are natural number multiples of peak frequency or frequencies and that can be used to mask ambient sound(s); and modulator(s) that modulate a plurality of carrier waves with baseband signal(s).