How can I switch off sound when I am writing notes?

I've recently bought a new laptop and thus installed the newest version of MuseScore
, which is 2.0.3. It looks quite different from older versions so I am maybe embarrassed
with the unfamiliar feature, but if anyone can help me, it would be most helpful.

My problem is I cannot switch off the sound that is produced simultaneously as I place a note.
In older versions, I could turn it off simply by clicking "MIDI Input" button to disable the
function. With this newer version, however, the sound is produced regardless of the state of the
button. I cannot find anything else to switch off the function.

I do not need the sound. (Of course I can turn the volume of PC speakers down to null not to
hear the sound, but what I want to do is turn off the unnecessary function itself because
it maybe slows down the application. )

Thanks in advance for your help.