"Sound output" refers to the audio that is produced or heard from a device, such as speakers or headphones. It is the sound that is played or emitted by a device for you to hear. Full definition
In addition, the A3 and A5 will come with adjustable audio, which will adapt to noise levels in your surrounding environment to adapt and enhance sound output of the devices. (androidauthority.com)
It offered good sound output with the dual front facing stereo speaker. (phoneradar.com)
The headphones that come with the phone offer average quality sound output. (gadgets.ndtv.com)