Making a room quieter without rebuilding it
Soft things in the right places do most of what expensive panels promise.
Hard, parallel surfaces are what make a room sound harsh: bare walls facing each other, glass, a wooden floor. You do not need acoustic panels to fix that — you need soft mass wherever sound bounces.
A rug, heavy curtains, a bookshelf with uneven contents and a throw over the back of a chair will change a room more than most people expect. Corners matter most; that is where low sound gathers.
Do it in stages and listen after each one. Clap once in the middle of the room: when the sharp ring turns into a short, dull thud, you are done.