Methods and apparatus for processing spatialised audio

An apparatus for sound reproduction of a series of audio signals, said apparatus comprising:

• audio input means for the input of said series of audio signals having substantially no spatial components;
• a sound component creation means connected to each of said audio signals and adapted to convert said audio signal to a corresponding sound information signal having spatial components describing the sound as it arrives at a listening position in a particular sound environment;
• headtracking means for tracking a current head orientation of a listener listening to said sound information signal via sound emission sources and to produce a corresponding head orientation signal;
• sound information rotation means connected to said sound input means and said headtracking means and adapted to rotate said sound information signal through the multiplication of said sound information by a geometric rotation matrix having coefficients determined by said head orientation signal, to a substantially opposite degree of orientation of said current head orientation of said listener to produce a rotated sound information signal;
• and
• sound conversion means connected to said sound information signal rotation means for converting said rotated sound information signal to corresponding sound emission signals for outputting by said sound emission sources such that the spatial components of said sound information signal are substantially maintained in the presence of movement of the orientation of the head of said listener.

An apparatus for sound reproduction of a sound information signal having spatial components describing the sound as it arrives at a listening position in a predetermined sound environment, said apparatus comprising:

• sound input means adapted to input said sound information signal having spatial components describing the sound as it arrives at a listening position in a predetermined sound environment;
• sound conversion means connected to said sound input means for converting said sound information signal to corresponding sound emission signals for outputting by said sound emission sources such that the spatial components of said sound information signal are substantially maintained in the presence of movement of the orientation of head of said listener through the multiplication of said sound information signal by a geometric rotation Matrix having coefficients determined by a head orientation signal derived from a current orientation position of the head of said listener, and
• said sound conversion means further comprising, for each sound emission source, sound component mapping means mapping each of the spatial components of said sound information signal to a corresponding component sound emission source signal and component summation means connected to each of said sound components mapping means and adapted to combine said component sound emission source signals to produce said corresponding sound emission signal for outputting by said sound emission source.

A method for reproducing sound comprising the steps of:

• inputting a sound information signal having spatial components describing the sound as it arrives at a listening position in a predetermined sound environment;
• determining a current orientation of a predetermined number of sound emission sources around a listener;
• rotating said sound information signal in a direction substantially opposite to said current orientation through the multiplication of said sound information signal by a geometric rotation matrix having coefficients determined by the current orientation of said sound emission sources to form a rotated sound information signal;
• and
• outputting said rotated sound information signal on said sound emission sources so that the apparent sound field is fixed in external orientation, independent of movement of the orientation of said predetermined number of sound emission sources.