Sharp PC-MM1 series Operation Manual page 65

You can adjust the output volume on Windows by clicking the speaker
symbol on the taskbar or use Fn + F3 ( ) or F4 ( ) keys
combination.
Connecting Headphone
Use the headphone with an impedance of 8Ω.or more (32Ω is recommended.)
Headphone
Headphone/Audio Output Jack
4
Stereo Mini Plug
4-15