If the basic assumption that prehistoric monuments were erected as focal points for human interaction beyond the normal is accepted, it may also be accepted that they were intended to imbue certain behavioural characteristics in visitors through manipulating/exploiting the way folks think... to control them, if you like. An obvious example from my experience is erecting a funerary cairn on a mountain top ensuring intense sensory perceptions are a given. The impact of light, or lack of it, forcing visitors to crawl along passageways... to experience an electrical storm upon a mountain top is guaranteed to have a massive impact. Yeah, sound. Sound is a major facet of our sensory perception so it would surely be pedantic and churlish to dismiss the possibility of it being taken into account by the original designers of some monuments, where the peculiar landscape or architectural circumstances allowed, merely because we can't be 100% sure what the monument originally looked like?
In my experience it is a fact that some sites possess a far more intense vibe than others... for me. There are many contributing factors such as personal well being on the day, the weather, light, time of year. I've been to a number of sites where to move but a few feet one way or the other has invalidated quite specific views, where quite intense and distinctive echoes are no longer present. It can not be proven that these aspects were intentional; but then again by what authority can it be stated that they were not intentional? As with all theories we need a body of accumulating evidence to support the notion that auditory elements played a contributing role to human experiences at prehistoric sites. To my mind the best way of getting that is to get out there and put them to the test.