10 Soothing Sounds:Built-in 10 soothing sounds white noise/lullaby 1/cricket/sea waves/clock/birds/heartbeat/lullaby 2/stream/lullaby 3, which can keep little ones feel safe and relaxed, then drift off to sleep slowly. Convenient Timer and Volume Adjustable Function :You can set timer options between 15/30/60min to help conserve energy; adjustable volume design enables you to create a best sleeping environment for your baby. Automatic Noise Detection Mode:If continuous noise is detected for 10s, just turn on the music by yourself, the sleep machine will stop automatically after 15min of playing, and enter the detection mode again, looping all the time. Built-in Rechargeable Battery:Built-in 300mAh battery that can be recharged by the included USB cable, 1 hour fast fully charge and last for 23 hours working time, no need to worry about power off problems. Compact and Portable:Compact and lightweight, very convenient to carry around and suitable for travel use; comes with a lanyard, you can hang the sleep machine on baby buggy or other place to save space.