An information providing system comprising: a sound emission device, adapted to emit, as a sound wave, identification information modulated to a sound signal; an identification information resolution server that is connected to an information communication network and includes a mapping table in which the identification information, valid time information, which indicates a range of valid time of the identification information, and address information of a content corresponding to the identification information are stored to be associated with each other; and a mobile terminal device that includes a sound pickup unit, adapted to pick up the sound wave emitted from the sound emission device, a demodulation unit, adapted to demodulate the identification information from the picked up sound wave, an identification information resolution unit, adapted to transmit the demodulated identification information to the identification information resolution server and thus acquire the address information, and a network access unit, adapted to access the content by using the acquired address information, wherein the identification information resolution server receives the identification information from the mobile terminal device, refers to the mapping table by using time information and the identification information and returns the address information of a corresponding content to the mobile terminal device when the time information is within the range of valid time indicated by the valid time information; and the identification information resolution server is adapted to reply to indicate that the identification information is invalid when the time information is out of the range of valid time indicated by the valid time information, wherein the sound emission device is a broadcasting receiving device, the sound wave is transmitted from a broadcasting station, as a sound wave in a broadcasting program or promo, and the identification information resolution server identifies address information for accessing a content relating to the program or promo, based on the received identification information, wherein the time information indicates at least one of a time at which the sound pickup unit of the mobile terminal device picks up the sound wave, a time at which the demodulation unit of the mobile terminal device demodulates the identification information and a time at which the identification information resolution unit of the mobile terminal device transmits the identification information to the identification information resolution server. a sound emission device, adapted to emit, as a sound wave, identification information modulated to a sound signal; an identification information resolution server that is connected to an information communication network and includes a mapping table in which the identification information, valid time information, which indicates a range of valid time of the identification information, and address information of a content corresponding to the identification information are stored to be associated with each other; and a mobile terminal device that includes a sound pickup unit, adapted to pick up the sound wave emitted from the sound emission device, a demodulation unit, adapted to demodulate the identification information from the picked up sound wave, an identification information resolution unit, adapted to transmit the demodulated identification information to the identification information resolution server and thus acquire the address information, and a network access unit, adapted to access the content by using the acquired address information, wherein the identification information resolution server receives the identification information from the mobile terminal device, refers to the mapping table by using time information and the identification information and returns the address information of a corresponding content to the mobile terminal device when the time information is within the range of valid time indicated by the valid time information; and the identification information resolution server is adapted to reply to indicate that the identification information is invalid when the time information is out of the range of valid time indicated by the valid time information, wherein the sound emission device is a broadcasting receiving device, the sound wave is transmitted from a broadcasting station, as a sound wave in a broadcasting program or promo, and the identification information resolution server identifies address information for accessing a content relating to the program or promo, based on the received identification information, wherein the time information indicates at least one of a time at which the sound pickup unit of the mobile terminal device picks up the sound wave, a time at which the demodulation unit of the mobile terminal device demodulates the identification information and a time at which the identification information resolution unit of the mobile terminal device transmits the identification information to the identification information resolution server.