Increasingly rapid growth of information technology and computer networks has resulted in the transfer of digital information to be considered further. The main concern of the owners and producers of digital products is to protect them against unauthorized copying and distribution. Aneffective method to solve this problem is digital watermarking technique. The goal of audio digital watermarking is to enter a series of hidden information into an audio file in a way that it would become unlistenable and robust against signal process attacks. One of the challenging categories in watermarking field has always been the amount of data that can be embedded in an audio file. In this article it has been tried to have a comprehensive overview on different ways of increasing the capacity of the audio watermarking and then advantages and disadvantages of each are discussed and examined.