Audio Signal Processing Device for Headphone Sound Field Simulation
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Solution Overview
Problem
Multichannel surround sound systems using 2-channel headphones struggle to accurately reproduce sound quality and sound field when simulating speaker environments, as headphones are fixed on the listener's head, whereas speakers are not, leading to inconsistent distances and angles, resulting in excessive reverberation or inadequate sound localization.
Innovation Solution
An audio signal processing device and method that performs signal processing to fluctuate sound images slightly by mixing audio signals from other channels and convolving them with head-related transfer functions, synchronizing sound image localization across channels to replicate the speaker environment effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If virtual sound image localization is used to simulate speaker positions, then sound localization is improved, but sound quality and sound field reproduction deteriorate due to excessive reverberation and inability to capture head movement effects
Solution Approach 1:
The patent applies dynamics by introducing temporal variation to the head-related transfer function parameters. Instead of using fixed HRTF values for static speaker positions, the system dynamically adjusts HRTF parameters (azimuth, elevation, distance) over time to simulate natural head movements. This allows the sound field to change dynamically, reproducing the effect of head movement that occurs during actual speaker listening, thereby resolving the contradiction between accurate localization and realistic sound quality reproduction
Solution Approach 2:
The patent changes physical parameters of the HRTF function by varying azimuth, elevation, and distance parameters over time. These parameter changes simulate the effect of head movement relative to fixed speakers, transforming the static virtual sound image localization into a dynamic representation that captures natural listening behavior. This parameter variation resolves the contradiction by maintaining accurate localization while adding realistic sound field characteristics
2Ease of operation
If headphones are firmly fixed on the listener's head, then ease of operation is improved, but sound field reproduction deteriorates because head movement relative to speakers cannot be simulated
Solution Approach 1:
The patent replaces the mechanical approach of physically moving the listener's head with a signal processing approach. Instead of requiring actual head movement to change sound field characteristics, the system uses digital signal processing to vary HRTF parameters, substituting mechanical movement with computational manipulation of audio signals. This resolves the contradiction by maintaining headphone stability while synthesizing the acoustic effects of head movement
Solution Approach 2:
The patent introduces an intermediary computational layer between the fixed headphones and the listener's ear. The HRTF parameter variation acts as an intermediary that translates the static headphone position into dynamic sound field characteristics, mediating between the fixed mechanical position and the desired dynamic acoustic experience. This intermediary processing resolves the contradiction by decoupling physical stability from acoustic dynamics
3Area of stationary object
If reverb components are added to reproduce a wide sound field, then sound field expansion is improved, but sound quality deteriorates due to excessive reverberation
Solution Approach 1:
The patent applies dynamics by making the sound field characteristics time-varying through HRTF parameter modulation. Instead of using static reverb components that create excessive reverberation, the system dynamically adjusts directional parameters to simulate head movement, which naturally varies the sound field experience over time. This dynamic approach expands the perceived sound field width while maintaining sound quality by avoiding excessive static reverberation
Solution Approach 2:
The patent employs periodic action by introducing temporal variation cycles in the HRTF parameters. The systematic variation of azimuth, elevation, and distance parameters over time creates a periodic modulation of the sound field that simulates natural head movements. This periodic variation expands the effective sound field width while maintaining audio clarity, resolving the contradiction between sound field expansion and sound quality preservation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances sound quality and expands the sound field, providing a more immersive experience by accurately simulating the speaker environment without the need for head movement sensors, effectively reproducing the sound field as if speakers were actually disposed.
Implementation Method 1
head-related transfer functions for the respective channels are measured by, for example, reproducing impulses. Then, the impulse responses of the head-related transfer functions obtained by the measurement may be convolved with audio signals
Implementation Method 2
performing signal processing to fluctuate sound images slightly by mixing audio signals from other channels and convolving them with head-related transfer functions
Data Source
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AI summary
Provided is an audio signal processing device including a signal processing section that changes, at a time of generating and outputting 2-channel audio signals to be subjected to sound reproduction by two electroacoustic transducing means located at positions in the vicinities of both ears of a listener, from audio signals of a plurality of and more than two channels, virtual sound image localization positions on a circle around the listener, across the virtual sound image localization positions, the virtual sound image localization position that is supposed for each of the plurality of channels of audio signals provided on the circle.