Disclosed is a method, a system, and an apparatus for providing a sound source, which has been encoded by using an audio codec, as a ringback tone alternative having an improved quality by adaptively applying various audio codecs according to the service type so that, when a mobile communication terminal is provided with a ringback tone alternative by separately applying an audio codec and a voice codec to a ringback tone provision section and a voice communication section, respectively, it is unnecessary to individually and additionally change or modify a number of devices in a mobile communication network, but a specific device in an intelligent network controls other devices based on overall consideration of the ability of the mobile communication terminal, the type of the ringback tone alternative, etc.