Can my neighbour do something to quieten noisy flue?

My neighbour's boiler flue extends out of their exterior kitchen wall about 1 foot (maybe more). When boiler is operating the flue hums quite loudly which I can hear in my kitchen (above their kitchen) and even in my lounge at front of my maisonette and also upstairs in the bathroom (over my kitchen) and in my bedroom which is at the front of the maisonnette. In fact I can hear it in all rooms. It is now driving me mad. Is there anything they can do to eliminate or reduce the noise the flue makes?