Android中有如下几种音频流：
- AudioManager.STREAM_MUSIC /** The audio stream for music playback */
- AudioManager.STREAM_RING /** The audio stream for the phone ring */
- AudioManager.STREAM_ALARM /** The audio stream for alarms */
- AudioManager.STREAM_NOTIFICATION /** The audio stream for notifications */
- AudioManager.STREAM_SYSTEM /** The audio stream for system sounds */
- AudioManager.STREAM_VOICECALL /** The audio stream for phone calls */