Dipole Steering Unit for Stereo Widening in Compact Audio Devices
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Solution Overview
Problem
Conventional devices with two transducers, such as laptops and smartphones, suffer from narrow sound reproduction due to their small loudspeaker span angles, resulting in a 'mono-like' experience, as the transducers are typically placed close together, limiting the spatial perception of stereo recordings.
Innovation Solution
The use of a dipole steering unit that produces dipole signals with specific azimuth angles to create increased interaural-level differences, allowing for a stereo widening effect by emitting more energy to one side than the other, thereby localizing sound sources outside the line segment between the transducers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If transducers are placed close together in a single cabinet, then device size is reduced, but spatial perception of stereo recordings deteriorates
Solution Approach 1:
The patent applies asymmetry by creating unequal sound pressure levels at the left and right ears through dipole signal processing. The system intentionally generates asymmetric acoustic fields where one ear receives stronger sound than the other, mimicking natural listening conditions and enabling accurate spatial localization despite symmetric transducer placement in the device.
Solution Approach 2:
The system changes acoustic parameters by manipulating sound pressure levels and phase relationships through dipole steering. By adjusting the amplitude and phase of signals sent to each transducer, the system creates variable interaural level differences that encode spatial information, transforming the acoustic field characteristics to overcome the physical constraints of compact transducer spacing.
2Loss of information
If beamforming is used to reflect acoustic beams on walls, then spatial effect is improved, but device complexity and transducer quantity increase
Solution Approach 1:
The patent extracts the essential spatial localization cues from complex beamforming systems by focusing only on interaural level differences. Instead of using multiple transducers to create reflected acoustic beams, the system extracts and applies only the necessary parameter (sound pressure level difference between ears) to achieve spatial effect with minimal transducers.
Solution Approach 2:
The system creates a simplified copy of the spatial effect by generating artificial interaural level differences that mimic natural acoustic propagation. Rather than physically reflecting sound beams off walls, the system copies the essential characteristic of spatial sound (unequal pressure at each ear) through electronic signal processing and dipole radiation patterns.
3Loss of information
If conventional crosstalk cancellation is used, then spatial perception is improved, but system becomes sensitive to ill-conditioned filter inversion
Solution Approach 1:
The patent converts the potential harm of ill-conditioned filter inversion into a benefit by using dipole steering that naturally produces the desired interaural level differences. Instead of relying on unstable filter inversion to cancel crosstalk, the system uses the dipole radiation pattern's inherent directional characteristics to achieve spatial effect, turning a problematic mathematical operation into a physically-based solution.
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
This approach enhances spatial effects for small loudspeaker span angles, is computationally simple, and can be adapted to various setups without requiring many transducers, providing a robust and effective stereo widening effect even outside the sweet spot.
Implementation Method 1
a first dipole steering module adapted to produce a first dipole signal based on the first audio channel signal, a second dipole steering module adapted to produce a second dipole signal based on the second audio channel signal
Implementation Method 2
the first dipole steering module and the second dipole steering module are adapted to produce the first dipole signal and the second dipole signal such that, when output via a transducer unit, a first zero sound propagation direction of the first dipole signal has a positive azimuth angle with regard to a steering reference direction, and a second zero sound propagation direction of the second dipole signal has a negative azimuth angle
Data Source
AI summary
An apparatus and a method for enhancing a spatial perception of an audio signal are provided creating increased interaural-level differences. To obtain this effect, two dipoles are used: one for producing a left audio signal and one for producing a right audio signal.