As the method of providing an audio signal to the user is digitized in the analog method, a wider volume area may be expressed. In addition, volume of the audio signal is diversified according to the content corresponding to the audio signal. This is because in an audio content production process, the intended loudness of the audio content may be set differently for each audio content. Accordingly, international standards groups such as the International Telecommunication Union (ITU) and the European Broadcasting Union (EBU) have issued standards for audio loudness. However, there is a problem that it is difficult to apply the standards issued by the international standards groups because the method and the standards for measuring loudness are different in each country.
The producers of the contents try to produce the contents with relatively loudly mixed contents and provide them to the users. This is because of the psychoacoustical characteristic which is recognized that the sound quality of the audio signal is improved when the volume of the audio signal is increased. As a result, there is a competitive landscape called a Loudness War. This causes a difference in loudness between contents or a plurality of contents internally, and the user repeatedly adjusts the volume of the apparatus on which the contents are reproduced, and it may suffer from the inconvenience. Therefore, there is a need for a technique for normalizing the loudness of the audio content for the convenience of the user using the content reproduction apparatus.