Hello,
I've updated the game now to only use one sound for center, left and right and to pan this sound accordingly to the left and right, that fixed the volumes as well as well as the not hearing the canes and skateboards on the left and right properly. The sounds of not hearing the coins before picking them up is intentional since you only should hear when you collected coins. I'm more used to mainstream online games I guess, even if I'm blind since birth I played a game on a german website where you flew with a UFO and you collected stars and dodged commets and you only heard the "ding" sound of the stars when you collected them, so maybe that's why I'm used to such things and had this idea in mind as well.