You are right...tone of voice & how you explain matters..
I have a very soft voice. That and not being a very LOUD speaker has helped be an effective IT person. I have a very calming effect which helps alot. But, sometimes it's difficult to keep that calm voice when dealing with an irate user with their IT issue. So, I know my normal calm voice raises a bit.
Even when trying to explain in layman's terms or in terms the user can understand, it's like there's still that language barrier. Or, if you even take the time to explain in detail, in the end, the user will say why didn't you explain it another way. it's like they are mad at you because you took the long 5 minute route when in actuality it would've taken 30 seconds?