Question
we have a narrow backyard (20ft) and a neighbor who plays their boom box loudly while swimming laps.  we have a 3 ft high  retaining wall that is 12ft from family room slider.  there is a 8ft hedge on our neighbor's side.

suggestions for a structure that would deflect the noise?  we must not install a solid fence due to ccr's requiring "green belt" fencing between the houses.

Answer
Hello Dea, the best protection against noise, since time began, is still air. This means that a wooden fence, with two layers, would protect you best. Make a fence with two layers that traps an area of still air between two layers of fencing (preferably 'close board' fencing) and you will reduce the sound problem in more than any other way!

Jonathan.