Sealing vent in bedroom

I'd appreciate if someone could advise me of the best way to seal an air vent in my bedroom unfortunately the bedroom is close to a road and the air vent. Let's in quite a lot of noise quite often. I'm awoken in the early morning by the sound of bin lorries any occasional car with one of those overly loud exhausts

RainInSummer

Before everyone comes along to tell you you'll die a horrid death by mould poisoning if you block it, there's sound reducing vents that have internal baffles in them to drop the sound levels while still providing airflow.

https://www.greentherm.ie/product/super-acoustic-controllable-wall-vent/

No experience of these but will probably be fitting one in my bedroom soon as the existing vent is directly above the oil boiler and pretty much fills the room with fumes when the boiler is on.

10-10-20

If you don't fancy that price, then look at this one:

https://www.goodwins.ie/products/stadium-anti-draught-black-hole-ventilator-bm725-terracotta-outer-cowl-3461400.html

It's not an easy fitment though, I had to drill out my existing vent and fit this in its place.