Using the MATLAB audio toolbox, we tested the performance of our loudspeaker parameters using sound propagation simulation. We entered the room characteristics (length, width, height, and loudspeaker locations) into our models and converted the frequency-domain output data to a time-domain model. We configured the output of the time-domain model as a series of movie frames, which we combined to show an animation of the propagation of the sound wave through the room using the MATLAB movie function.

The animation clearly revealed individual beams and their frequency dependence. At low frequencies, we had little beam formation, which is acceptable because the type of content we would like to beam (e.g., TV commentary) typically has relatively little energy at very low frequencies anyway. At higher frequencies we saw additional unwanted beams forming. We examined the results to find out whether these extra beams would cause effects audible to users.

Because the output of our modeling work includes a complex transfer function for every point in the room, we ran one further check on the behavior of the system. We took the response at two points spaced about 20 cm apart (the width of a human head) and convolved the response with a real audio signal, such as music or a television commentary. We then output the results of our MATLAB calculations as an audio stream and listened to the result. These simulations enabled us to hear what the real audio would sound like at any point in the room, giving us insight into the system’s sound quality and intensity.

As well as varying the sound level at different points in the room, we can use this same technology to feed different audio signals to different parts of the room. One person can listen to classical music while another listens to a TV program. We can place the different sound channels anywhere in the room.