Patent ID: 8515104

Claim:
An apparatus for binauralizing a set of one or more audio input signals comprising: a binauralizer implementing one or more pairs of binaural filters, one respective pair for each of the audio signal inputs, each pair of binaural filters having a left ear output and a right ear output, each pair of binaural filters representable by a left ear binaural filter and a right ear binaural filter, respectively, each pair of binaural filters further representable by a sum filter and a difference filter related to the left and right ear binaural filters, each filter having a respective impulse response that characterizes the filter, wherein at least one pair of binaural filters is configured to spatialize its respective audio input signal to incorporate a direct response to a listener from a respective virtual speaker location, and to incorporate both early echoes and a reverberant response of a listening room, and wherein for the at least one pair of binaural filters configured to spatialize: the time-frequency characteristics of the sum filter are different than the time-frequency characteristics of the difference filter, with the sum filter reverberation time smaller at all frequencies than each of: the difference filter reverberation time, the left ear filter reverberation time, and the right ear filter reverberation time; and the sum filter reverberation time varies more across different frequencies than the respective variation over frequencies of the left ear filter reverberation time and of the right ear filter reverberation time, with the sum filter reverberation time decreasing with increasing frequency, such that the one or more audio input signals filtered by the pair of binaural filters generate output signals that are perceived as spatialized when played through headphones and sound good when played monophonically after a monophonic mix achieved by downmixing or by playing over relatively closely spaced loudspeakers, wherein for the at least one pair of binaural filters, the transition of the sum filter impulse response to its negligible level occurs gradually over time in a frequency dependent manner over an initial time interval of the sum filter impulse response, wherein for the at least one pair of binaural filters, the sum filter decreases in frequency content from being initially full bandwidth towards a low frequency cutoff over the transition time interval.