Seamless switch to battery power. Portable for travel.
Magnet for kids to play with.
This one has been our favorite sound machine and have bought more than one. We had a power outage with our first baby while she slept at night and the sound machine automatically switched from AC to battery power, so that got us hooked. We have had Duracell batteries explode in one, so that was only usable when plugged in. Maybe the Eneloops would have fared better.
If the sound cuts out for no reason, it may not be broken. The kids may press the timer button when you aren’t looking. Just turn it off and back on.
If you keep batteries in it, check them periodically.