Vinyl Blinds

Thanks for the responses. I will probably be looking at curtains especially for the side of the room that has no furniture.

I’ve got a good amount of glass as well and went to the heavy fabric blinds as mentioned above. Works very well.

Vinyl is a hard surface, and for obvious reasons, the sound will 'bounce' off this surface, no matter how thick the Vinyl.  I would recommend a heavier cloth drapery effect for a couple of these windows, so you can realize a small amount of acoustic room treatment...

Most banquet halls that have the the large acoustically baffled room dividers also have vinyl backed drapes to deaden the sound.

You can also get mass loaded vinyl for even better absorption

How Is Mass Loaded Vinyl Used in Soundproofing? | Acoustical Solutions

Soundproofing Curtains and Blankets (tmsoundproofing.com)

https://www.soundproofing.org/infopages/curtains.htm

Soundproofing a Band Rehearsal Space | Acoustical Solutions

Sports & Entertainment Venue Acoustics | Acoustical Surfaces

The list goes on :-)

I have tried the mass loaded vinyl with great effect - still have one piece backed with foam to allow it to vibrate - on top of a bookshelf - works like a charm

Regards - Steve