Hi @Todsta,
Thank you for your question and welcome to the Bunnings Workshop community, it is great to have you with us.
Did you have any photos of the windows you were looking to soundproof?
There are general tips I can offer, but our members will be able to offer more specific advice if they can see the windows you're looking to soundproof. Let me know if you need some assistance uploading photos, I'm more than happy to help.
The general rule in soundproofing is to reduce the air transfer and dampen any vibration.
Reducing air transfer can be done by sealing any gaps using a sealant such as No More Gaps. Gaps that are essential for the movement of the window can be closed with the use of weather seals.
You may also get some value from sticking Acoustic Pinboard Grey to the windows using mounting tape and hanging heavy curtains such as these Windoware 120 x 223cm Linen Urban Room Darkening Eyelet Curtain.
You might also like to check out these discussions and articles for some guidance:
I've included the last one because many of the principles for winter-proofing your home will also reduce sound transfer.
Let me know if you have any questions or require assistance uploading images.
Jacob
