On my H10-13X there is a mono/stereo switch hidden in the battery box below the battery. Mine has never produced any particular buzzing noise, but the ENC system does produce 'anti-noise' that can be perceived as very light 'white noise' depending on how good your hearing is. This should only be noticable if you're in a very quiet environment. If you're using it in an aircraft with the engine running, you should get a very noticable drop in low frequency noise when you switch the ENC on. It should not produce any additional noises.