Multichannel Sound Signal Localization Using HRTF Dynamic Cue Filtering
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Solution Overview
Problem
Current stereoscopic audio technologies are less efficient in vertical surface sound image localization, failing to provide a realistic sense of elevation to the audience, as they do not account for changes in the head-related transfer function (HRTF) based on the audience's location.
Innovation Solution
A method and apparatus that apply a first filter corresponding to a predetermined elevation to an input sound signal to generate a multichannel sound signal, and a second filter is used to determine and adjust specific frequency ranges of the dynamic cue in the HRTF, applying a phase inverse, amplitude adjusting, or delay filter to remove or reduce the dynamic cue, thereby enhancing the sense of elevation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional stereoscopic audio technologies are used for vertical surface sound image localization, then the system complexity is low, but the sense of elevation is not realistic and the localization efficiency is poor
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing HRTF data for multiple elevation angles and audience positions. The system prepares filter coefficients in advance based on predicted audience locations and elevation requirements, so that when sound localization is needed, the pre-computed filters can be immediately applied without real-time calculation delays. This allows realistic vertical sound localization while managing system complexity through offline preparation.
Solution Approach 2:
The patent introduces HRTF-based filters as an intermediary between the audio signal and the audience's perception. These filters act as a mediator that transforms the audio signal according to the acoustic characteristics of sound traveling from specific elevations to the audience's ears. By using HRTF filters as an intermediary, the system achieves realistic elevation perception without requiring complex physical speaker arrangements.
2Measurement precision
If HRTF changes based on audience location are accounted for, then the sense of elevation becomes more realistic, but the processing complexity and computational requirements increase
Solution Approach 1:
The patent segments the continuous HRTF data into discrete frequency ranges and elevation bands. By dividing the audio spectrum into specific frequency bands and associating each band with particular elevation characteristics, the system can process localization with higher precision without needing to handle the entire frequency spectrum at full resolution. This segmentation reduces computational complexity while maintaining accurate elevation perception.
Solution Approach 2:
The patent changes parameters by selectively adjusting only the frequency ranges that contain dynamic cues related to elevation, rather than processing the entire audio signal. The system identifies specific frequency bands where HRTF variations occur and applies filtering only to those bands, leaving other frequency ranges unchanged. This parameter-based approach achieves precise localization while minimizing processing complexity.
3Reliability
If dynamic cues in frequency ranges are adjusted to account for HRTF changes, then the sense of elevation is enhanced, but the sound signal quality may deteriorate
Solution Approach 1:
The patent applies local quality by making different parts of the sound signal have different processing characteristics. Specifically, only certain frequency ranges that contain elevation-related dynamic cues are filtered and adjusted, while other frequency ranges remain unprocessed or are processed with different filter settings. This localized approach enhances the sense of elevation in critical frequency bands without degrading the overall sound quality, as non-critical frequency components are preserved.
4Stability of the object's composition
If filters are applied to remove or reduce dynamic cues, then the sense of elevation is stabilized, but the adaptability to different audience positions decreases
Solution Approach 1:
The patent applies dynamics by making the filtering system adaptable to different audience positions rather than using fixed filters. The system dynamically selects or adjusts filter parameters based on the audience's location, allowing the same system to maintain stable elevation perception for multiple different positions. This dynamic approach enables the filters to remove or reduce dynamic cues appropriately for each specific audience position while maintaining overall adaptability.
Data Source
AI summary
Provided are a method and apparatus for localizing a multichannel sound signal. The method includes: obtaining a multichannel sound signal to which sense of elevation is applied by applying a first filter to an input sound signal; determining at least one frequency range of a dynamic cue according to change of a head-related transfer function (HRTF) indicating information regarding paths from a spatial location of an actual speaker to ears of an audience; and applying a second filter to at least one sound signal, corresponding to the determined at least one frequency range, of at least one channel in the multichannel sound signal to change the at least one sound signal so as to remove or to reduce the dynamic cue when the multichannel sound signal is output.