Abstract: A low-power sound wave reception method in a computer which includes a microphone, a memory which stores at least one reference pattern, and a computer processor is provided. The low-power sound wave reception method includes: when a sound wave signal having an intensity greater than or equal to a threshold value is detected by the microphone, comparing the sound wave signal and the at least one reference pattern stored in the memory; and when there is a reference pattern matching the sound wave signal, turning on the computer processor, and deactivating the reference pattern matching the sound wave signal (excluding the deactivated reference pattern from the comparing step).

Abstract: A method for transmitting sound waves using a time-varying frequency-based symbol includes the steps of: storing waveform data in a digital form; converting the waveform data in the digital form into an analog signal; and outputting the analog signal as sound waves through a speaker. Herein, the waveform data in the digital form includes a symbol the frequency of which changes with time within a sound wave band.

Abstract: Provided is a system for providing related content comprising the steps of: sensing a sound output from a content reproducing device for reproducing content (referred to as “main content”); converting the sensed sound into digital data; extracting an acoustic wave ID from the digital data; selecting related content corresponding to the acoustic wave ID; and displaying the related content in an image and/or speech by a mobile receiver.