People who are very close might hear it, but it shouldn't be loud enough to disturb people unless you're in a super quiet environment. The Q40 only has a moderate amount of clamp. Typically, a higher degree of clamp improves isolation by increasing the seal around your head (this usually comes at the expense of comfort, depending on the softness of the pads).
I have a fairly large head and low jawline, so the Q40 pad sits quite well and seals comfortably around my head without the need for pressure. too much. Those with stronger cheekbones and/or sloped jawline might not achieve as nice a seal with round pads and would find square/oval pads better suited. These are just huge generalizations though; it's different for everybody and every different headphone. The Q40 pads are softer and sit well on me, yet the DT770 pads are the same size but do not seal as well on my head. Some people put the Beyer pads on the Q40 and say that improves things for them.
TL;DR, you should be just fine.