Can anyone help with this problem? Perhaps other homeowners with the same unit have experienced similar problems?

I have the following unit: MAKE: Burnham MODEL: Beckett
SERIAL #: 951030-4502 MODEL: “AFG” Series Oil Burner
BOILER #: 27112735 DOE HTG CAP MBG = 121
Steam Square Feet: 379 Steam MBH = 91 Water MBH = 105

I recently changed to a new local oil company. The new Tech performed an annual maintenance check-up. This is not a new unit so it’s been serviced by other local techs. No problems were discovered but ever since his first maintenance check-up – the furnace has an additional muffled rumbling engine noise. Could the new Tech have altered something? It was once a quiet unit. Now the unit sounds just like truck engines driving by. No metal clanking just a loud rumbling engine sound. The sound seems to vibrate. Instead of sounding like a quiet residential furnace – it sounds more like a commercial furnace with greater capacity. I’ve asked him to return several times to remove the engine rumbling sound but he has not been unable to detect a problem. ANY SUGGESTIONS?

WILLIAM - HOMEOWNER