Weird sounds

Greetings, I would like to report two weird sounds that have been there for a long time but they don't sound like I should be worried, they are just strange so I am courious what could cause them. First one: After car warms up and let's say, I start to move and I press just around 10-20% of the throttle, there will be some sort of "hooting" sound comming from the back, I suppose fuel pump. By hooting I don't mean something like whining, best described would be a muffled car horn in the distance.As soon as I give the car over 20% throttle, sound stops. Second sound: also appears after car warms up but it comes from what I hear,right side of the engine bay. That one is a bit more worrying because it sounds like a tensioner or belt whine and is best heard at 2000-2500rpm, also the pitch of the sound increases as the revs go up,but it is almost totaly gone above 2500rpm.

Re. hooting sound - try opening the fuel cap & see if pressure is released & sound stops. Mine has always made this noise especially in hot weather.

Thanks for reply, yes I usually have build up pressure in the tank, not sure how normal that is.