Virtual Surround Sound Filtering for Headphone Sound Externalization
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Solution Overview
Problem
Existing virtual surround sound systems using headphones fail to effectively simulate natural sound localization, as they do not accurately model the combination of head-related and room impulse responses, leading to sounds appearing to originate from the listener's head rather than distant locations.
Innovation Solution
The method involves filtering a source audio signal with a combined room impulse response, which is a crossfaded mixture of monophonic and stereophonic responses, and a head-related impulse response, to accurately model the acoustic effects of the environment and human anatomy, thereby enhancing sound externalization and localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional stereo headphones are used for virtual surround sound, then portability and ease of use are improved, but sound externalization and natural localization are worsened
Solution Approach 1:
The patent applies parameter changes by modifying the audio signal parameters through convolution with HRTF and room impulse response filters. This transforms the stereo signal parameters to include spatial characteristics that simulate distant sound sources, thereby improving sound externalization while maintaining headphone ease of use
Solution Approach 2:
The patent introduces intermediary elements (HRTF filters and room impulse response filters) between the audio source and the listener's ears. These filters act as mediators that add spatial cues and environmental characteristics to the sound signal, enabling externalization without requiring physical surround speakers
2Measurement precision
If only head-related impulse response filtering is used, then sound localization is improved, but environmental realism and externalization are worsened
Solution Approach 1:
The patent merges two separate filtering operations: head-related impulse response filtering and room impulse response filtering. By combining these filters in sequence, the system simultaneously achieves accurate sound localization (through HRTF) and environmental realism (through room impulse response), resolving the contradiction between the two requirements
3Device complexity
If monophonic room impulse response is used, then computational simplicity is improved, but spatial accuracy and externalization are worsened
Solution Approach 1:
The patent applies local quality by using different types of room impulse responses for different frequency ranges. Low frequencies use monophonic room impulse response for simplicity, while high frequencies use stereophonic room impulse response for spatial accuracy. This frequency-dependent approach balances computational complexity with spatial realism
4Measurement precision
If stereophonic room impulse response is used, then spatial accuracy is improved, but low frequency realism and externalization are worsened
Solution Approach 1:
The patent applies parameter changes by using different room impulse response types for different frequency parameters. Stereophonic room impulse response is applied to high frequency components to maintain spatial accuracy, while monophonic room impulse response is applied to low frequency components to preserve realism and avoid artifacts
Data Source
AI summary
Aspects of the present disclosure relate to techniques for processing a source audio signal in order to localize sounds. In particular, aspects of the present disclosure relate to sound localization techniques which externalize sounds for headphone audio, such as a virtual surround sound headphone system. In various implementations, room reverberations and other acoustic effects of the environment may be more accurately modeled using improved room reverberation models. For example, in some implementations, the underlying source signal may be filtered with a filter representing a room impulse response that is a combination of a stereo room impulse response and a mono room impulse response. By way of further example, in some implementations the source signal may be filtered with a combined impulse response filter that is derived from binaural recordings of simulated impulses recorded in a desired reverberant environment.