The root cause of the buzz is "EMFs" or Electro-Magnetic Fields. When current flows through a wire, it creates a magnetic field around it. When it's Edison's Direct Current, like on your car's wiring or the Tube's third rail, the magnetic field does not change. When it's Tesla's Alternating Current, like mains wiring, the magnetic field reverses in the UK 100 times a second (50 cycles/sec). This ever-changing magnetic field is what makes transformers work, which makes power to your house a possibility.
The magnetic field is proportional to current.
There is a rule that currents should be equal in all cables or conduits. This is because current travels in loops, and the current to your hob and the current returning are equal. The two wires' current, traveling in opposite directions, are equal and opposite. Held close together, they substantially cancel each other out. That prevents cable vibration in the walls.
However, inside junctions the wires separate somewhat. The it is possible for the wires to extend their magnetic field. The magnetic field can make the wire "buzz". this can damage the wire, so it's worth looking into. Much more importantly, it can expose a loose connection which can cause arcing, and wire or breaker damage.
Circuit breakers also use the magnetic fields. Power goes only one way through them (neutrals don't have breakers) so it is not canceled out. Also, breakers use a coil to intentionally amplify the magnetic field - this is how it trips the breaker on overload.
So there are several bits in there that can make noise in response to higher currents on a wire. If it's the breaker itself, that might be harmless -- but I would not tolerate it in any case, because it could mask other, dangerous sources of noise.