Sound coming through around window frame?

[MumNo2]

We live in a 1930s house which has 2 bay windows at the front (one downstairs and one immediately above). It feels like a lot of sound comes through them- I can hear the cars as they drive past.

Just wondering if anyone has any ideas of what may be causing this? Is it the age of the windows themselves? Or the sealant around it? Is there anything (other than replacing the whole window which we can't afford) that could help?

Are they replacement windows?

Post a pic, from the outside, showing how the frame meets the wall, and any gap or filler.

Is the bay made of brick, or is it made of air with an ornamental tile skin on the outside and plaster on the inside?