Headphone Sound Virtualization Using HRTFs and Reflections

The patent introduces head-related transfer functions (HRTFs) as an intermediary processing layer between the audio source and the listener's ears. HRTFs simulate the acoustic effects of sound traveling through the environment, including head, torso, and ear pinna effects, to create virtual sound sources that appear external to the listener. This mediator transforms the direct headphone signal into a spatially encoded signal that tricks the brain into perceiving external sound origins.

The patent creates virtual copies of acoustic environments by synthesizing reflected sound paths from virtual sound sources. Instead of requiring physical reflective surfaces, the system generates synthetic reflections that replicate how sound would bounce off walls, ceilings, and other surfaces in a real environment. These copied acoustic paths are then delivered through headphones to recreate the externalization effect of natural listening.

The patent pre-calculates and stores head-related transfer functions for various spatial positions and orientations before actual audio playback. HRTF data, which represents complex acoustic transformations, is prepared in advance and organized for rapid retrieval. This preliminary action eliminates the need for real-time computation of HRTFs during audio playback, significantly reducing processing complexity while maintaining high externalization quality.

The patent implements a hybrid approach where only certain acoustic parameters are processed in real-time while others are pre-computed. Specifically, the system pre-calculates HRTFs and radiation patterns, then applies only the necessary spatial transformations during playback. This partial processing strategy balances computational requirements with externalization quality, avoiding excessive real-time computation while achieving realistic sound externalization.

The patent divides the acoustic simulation into separate, independent components: direct sound paths, reflected sound paths, HRTF effects, and radiation patterns. Each component is processed separately and then combined to form the final audio output. This segmentation allows the system to selectively process only the most impactful elements in real-time while pre-computing less time-critical components, reducing overall computational energy requirements.

The patent utilizes pre-computed parameter sets for radiation patterns and reflective surface characteristics that can be quickly applied during audio processing. Instead of calculating complex acoustic transformations in real-time, the system selects from pre-determined parameter sets based on the virtual sound source position and orientation. This parameter-based approach dramatically reduces computational energy while maintaining accurate externalization effects.