You can test this very easily using an iPhone's speaker pointed towards a wall. When the speaker is more than an inch or two away, it is normal volume. However, when the speaker is nearly touching the wall, the sound is much louder. Why is this?
A rough diagram of a setup below:
the blue rectangle represents an iphone. In configuration A, the speakers point towards the observer, whereas in configuration B, the speakers point towards the wall. From the many times I have tried this, configuration B is louder than configuration A.