Sound: 82 Decibels at 1M away.
The size: It is very small (12cm lengths to 5cm high), but it is absolutely perfect.
In packaging, there are no chargers, just a cable so if you have a smartphone you can connect it to your charger, it is the same charge characteristics.
To change the music you need to press the Volume Up button for 5 seconds.
In terms of autonomy, I would say 4 hours / 5 hours depending on the volume.
Then a little advice: You know why the cables to charge (phone, etc ..) are short they are to avoid you use the unit during that load, it makes it lose its autonomy. So Avoid using your device while charging.