Boiler silent after oil pump replaced

[Bratan]

I recently had maintenance performed on my oil boiler. Guy couldn't get oil pump going after that (he spend about 4 hours) and it had to be replaced. I wasn't happy about the bill, but that's another story.
After pump was replaced, my boiler is now almost silent. I mean it was roaring like a jet engine ever since I moved to this house (almost 2 years ago), it was almost impossible to be next to it without earl plugs. It could be heard outside (boiler is in the basement)... I though it was normal.
Now it's more in the "infrasonic" range, very low frequency hum. I can't even hear it anymore on 1st or second floor.
I asked maintenance guy about it, and he just said it's normal but didn't elaborate. So I thought I'd ask here. Don't get me wrong, I really happy it's so quiet now, but is it normal? Can oil pump make such huge difference? Just seems to good...
It does heat the house and water

 

[Smooky]

There are a lot of reasons for noise from the boiler but with an old pump motor it may have been the bearings or seals were worn and that can cause a lot of noise. Some pumps are quiter than others too.
http://inspectapedia.com/heat/Oil_Burner_Noises.php

 

[Sponsor]

 

[Tom Sawyer]

Most likely the coupling was misaligned and now it's not