This sound can be approximated by adopting the posture to whistle a very low note, or blow out a candle. is produced with the tongue as low and as far back in the mouth as possible.

• 发此音的动作，大约有如吹出很低音的哨子，或者吹蜡烛。如要发出，舌头则要尽可能伸至最后和最低。