We tested this with a free phone app to a scientifically satisfying degree
The shocking answer is no, hedges do almost nothing to reduce noise. Whatever noisiness measurement you use, it’s the same on either side of the hedge.
- Light, thin wood fences reduce noise a little, barely noticeable
- Sturdy, thick wood fences reduce noise a bit more
- Stone walls reduce noise more than anything except an earth bank
That includes the broadleaf evergreen hedges that are marketed as blocking noise, even on this very website!
Laurel and Holly with their big, heavy leaves are no better than light, airy plants: they all do almost nothing to reduce sound.
When you’re talking to someone on the other side of a hedge, it probably feels like you need to raise your voice to be heard, but it’s not true.
Out of Sight, Out of Mind
What a hedge does is block sight, while being pleasant to look at itself.
A wall or fence can look nice, but never as nice as a green slice of forest. Walls or fences feel constrictive; the hedge is natural and embracing.
If you have a wall already, with no room for a hedge to hide it, your main options are climbers, rambling roses, or wire trained espaliers etc.