rumbling noise on groove coming from suction or pump?

[nikc]

Hello

I have recently started cutting after a year and a half of embossing with my MSS lathe.
Tests are going well; I have been making silent grooves and they sound pretty good (quiet) apart from a slight low rumbling.
I have turned suction off for a split second and think the rumbling reduces. I dont want to turn it off for any longer, as the swarf quickly tangles up.

So the rumbling could be coming from the noisy vaccum pump, or the air suction near the stylus.
Has anyone else had issue with this or heard of this? or am I making it up in my head?

Please help,

Nik