法苑珠林 36.107

36.107

如長阿含經云。其有音聲五種清淨。乃名梵聲。何等為五。一者其音正直。二者其音和雅。三者其音清徹。四者其音深滿。五者周遍遠聞。具此五者乃名梵音。

As the Dīrgha-āgama says: 'When a voice possesses five kinds of purity, it is then termed a Brahma voice (brahmasvara). What are the five? First, its tone is upright; second, its tone is harmonious and elegant; third, its tone is clear and penetrating; fourth, its tone is deep and full; fifth, it is heard everywhere afar. One who possesses these five is called having a Brahma voice.'