In an embodiment, the adaptive audio system utilizes upward-firing drivers to provide the height element. In general, it has been shown that incorporating signal processing to introduce perceptual height cues into the audio signal being fed to the upward-firing drivers improves the positioning and perceived quality of the virtual height signal.
For example, a parametric perceptual binaural hearing model has been developed to create a height cue filter, which when used to process audio being reproduced by an upward-firing driver, improves that perceived quality of the reproduction. In an embodiment, the height cue filter is derived from the both the physical speaker location (approximately level with the listener) and the reflected speaker location (above the listener).
For the physical speaker location, a directional filter is determined based on a model of the outer ear (or pinna). An inverse of this filter is next determined and used to remove the height cues from the physical speaker.
Next, for the reflected speaker location, a second directional filter is determined, using the same model of the outer ear. This filter is applied directly, essentially reproducing the cues the ear would receive if the sound were above the listener.
In practice, these filters may be combined in a way that allows for a single filter that both (1) removes the height cue from the physical speaker location, and (2) inserts the height cue from the reflected speaker location. FIG. 1600 is a graph that illustrates the frequency response for such a combined filter.
The combined filter may be used in a fashion that allows for some adjustability with respect to the aggressiveness or amount of filtering that is applied. For example, in some cases, it may be beneficial to not fully remove the physical speaker height cue, or fully apply the reflected speaker height cue since only some of the sound from the physical speaker arrives directly to the listener (with the remainder being reflected off the ceiling).