A method of processing an audio signal is provided. A decoding apparatus receives the audio signal, which includes a plurality of objects. The decoding apparatus further receives object information, object gain information, and object correlation information, preset presence information, preset number information, preset information based on the preset presence information and the preset number information, and preset rendering data. The preset information exists in a header region or in each frame. The decoding apparatus obtains a preset matrix from the user by an input unit of the audio decoding apparatus when the preset type information indicates the preset rendering data is defined by the user, and adjusts an output level of the plurality of objects for an output channel based on the object information and the preset matrix. The decoding apparatus outputs an adjusted audio signal including the plurality of objects with an adjusted output level.