there are woods near my house and if you walk through them there is a river where people like to party on a summers night. The river is roughly 500+ metres from my house. On a still night, with the windows open, I can hear the people at the river. I live in a sixth floor flat, and sometimes I can't hear the people round the corner playing music unless I am on the landing. It all depends on the direction the sound is coming from.
The question the defence asked of Botha was - could the witness hearing these arguments be 100% sure they came from OPs house from that distance. It's a rhetorical question really because of course the answer would be no.