Humbucking pickups are designed to reduce low-frequency hum from the power lines at 50 - 60 hertz. However, there are often rooms with sources of noise at higher audio frequencies. This “hash” can be distinguished from “hum” by noting that it changes when you adjust your tone control, while line frequency “hum” hardly changes at all. Humbucking pickups do not completely eliminate this high frequency noise.
If the bridge or tailpiece of your instrument is grounded, most of this noise disappears when either hand is touching the strings or the bridge, so it shouldn't cause serious problems in most playing situations. You can further reduce the noise by shielding the control compartment and shortening excess wire in the compartment, although our experience is that the improvement is relatively small.
