Abstract: It is demonstrated that the two forms of Green function in NAH technique give the same final results of sound field transformation. The quantitative relationships between the main parameters in NAH technique are deduced. The performance analysis of various filters is conducted. The methods for quickly calculating of the far-field directionality are given by use of the NAH field transformation and Helmholtz integration. Compared with DRL method, it is more applicable and precise for various acoustics sources.