1. An audio signal processing apparatus comprising: an index estimation unit adapted to receive three-dimensional image information and generate index information for applying a three-dimensional effect to an audio object in at least one direction from among right, left, up, down, front, and back directions, based on the three-dimensional image information; and a rendering unit adapted to apply a three-dimensional effect to the audio object in the at least one direction from among right, left, up, down, front, and back directions, based on the index information; and characterized by further comprising: a signal extracting unit comprising the audio object and receive adapted receive an audio signal comprising the audio object extract a plurality of audio signals from the received audio signal, and transmit the extracted signals to the rendering unit, and wherein the index estimation unit comprises: a sound source detection unit adapted to receive at least one extracted signal, analyze a direction angle or a direction vector and energy for each respective frequency band of the extracted signal, and determine whether the audio object corresponds to a static sound source or to a non-static sound source based on the analysis result; and an index generating unit adapted to generate index information so as to reduce a three-dimensional effect of the audio object in a case when the audio object corresponds to the static sound source, by setting a depth value of a depth information as an offset value and by setting sound extension information such that audio signals output from right and left channels have the same amplitude. 1. An audio signal processing apparatus comprising: an index estimation unit adapted to receive three-dimensional image information and generate index information for applying a three-dimensional effect to an audio object in at least one direction from among right, left, up, down, front, and back directions, based on the three-dimensional image information; and a rendering unit adapted to apply a three-dimensional effect to the audio object in the at least one direction from among right, left, up, down, front, and back directions, based on the index information; and characterized by further comprising: a signal extracting unit comprising the audio object and receive adapted receive an audio signal comprising the audio object extract a plurality of audio signals from the received audio signal, and transmit the extracted signals to the rendering unit, and an index estimation unit adapted to receive three-dimensional image information and generate index information for applying a three-dimensional effect to an audio object in at least one direction from among right, left, up, down, front, and back directions, based on the three-dimensional image information; and a rendering unit adapted to apply a three-dimensional effect to the audio object in the at least one direction from among right, left, up, down, front, and back directions, based on the index information; and characterized by further comprising: a signal extracting unit comprising the audio object and receive adapted receive an audio signal comprising the audio object extract a plurality of audio signals from the received audio signal, and transmit the extracted signals to the rendering unit, and a signal extracting unit comprising the audio object and receive adapted receive an audio signal comprising the audio object extract a plurality of audio signals from the received audio signal, and transmit the extracted signals to the rendering unit, and a sound source detection unit adapted to receive at least one extracted signal, analyze a direction angle or a direction vector and energy for each respective frequency band of the extracted signal, and determine whether the audio object corresponds to a static sound source or to a non-static sound source based on the analysis result; and an index generating unit adapted to generate index information so as to reduce a three-dimensional effect of the audio object in a case when the audio object corresponds to the static sound source, by setting a depth value of a depth information as an offset value and by setting sound extension information such that audio signals output from right and left channels have the same amplitude.