Azimuthal Waveguide Geometry for Uniform High-Frequency Dispersion
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Solution Overview
Problem
Conventional audio playback devices with tweeter systems have limited angular dispersion of high-frequency acoustic waves, resulting in non-uniform listening experiences for listeners positioned at different angles around the device, particularly in outdoor environments where angular dispersion is necessary to ensure all listeners can hear audio effectively.
Innovation Solution
The use of an electroacoustic transducer coupled with an acoustic waveguide having a housing that delimits an opening with a radial distance varying with azimuthal angle, maintaining a substantially constant acoustic path length and incorporating absorbers to reduce intensity variations, leading to uniform directivity and wider angular dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a conventional tweeter system is used, then the device structure is simple, but the angular dispersion of high-frequency acoustic waves is limited
Solution Approach 1:
An acoustic waveguide is introduced as an intermediary component between the tweeter and the surrounding environment. The waveguide has a specific geometry with a first opening at a first end and a second opening at a second end, allowing acoustic waves to propagate through it. This intermediary structure enables the waves to emerge at multiple angles, achieving wide angular dispersion while maintaining a relatively simple overall device structure.
Solution Approach 2:
The waveguide is divided into multiple sections along its length, with each section having different geometric characteristics. The first opening has a first cross-sectional area and the second opening has a second cross-sectional area, creating segmented zones that guide and disperse acoustic waves at different angles. This segmentation allows control over the angular distribution of emitted sound without requiring multiple separate transducers.
2Shape
If the radial distance of the opening varies with azimuthal angle, then uniform directivity is achieved, but the manufacturing precision requirements increase
Solution Approach 1:
The waveguide geometry is designed with parameters that vary systematically along its length and around its circumference. The cross-sectional area changes from the first opening to the second opening, and the radial distance of the opening varies with azimuthal angle according to a controlled profile. These parameter changes are designed to compensate for natural acoustic variations, achieving uniform directivity through geometric optimization rather than requiring ultra-precise manufacturing tolerances.
3Shape
If absorbers are added to reduce intensity variations, then sound distribution uniformity improves, but the device complexity increases
Solution Approach 1:
Absorbers are strategically placed at specific locations within the waveguide where they are most effective. Rather than uniformly distributing absorption material throughout the entire waveguide, the design places absorbers at particular azimuthal positions and depths where they can most effectively reduce intensity variations and back reflections. This localized approach achieves improved sound distribution uniformity while minimizing the addition of complex components.
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 configuration ensures that listeners at different locations around the playback device experience similar sound levels and quality, reducing the impact of back reflections and interference, and providing improved sound distribution in non-reverberant environments like outdoors.
Implementation Method 1
an electroacoustic transducer
Implementation Method 2
an acoustic waveguide in fluid communication with the transducer
Implementation Method 3
an absorber disposed between the axis and the axial wall and configured to attenuate acoustic waves within a predetermined frequency band
Implementation Method 4
The opening has a dimension in a direction aligned with the axis that varies with an azimuthal angle about the axis, thereby reducing a variation of intensity around the axis of acoustic waves generated by the transducer and emitted from the opening
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
A playback device comprises an electroacoustic transducer; an acoustic waveguide in fluid communication with the transducer; and a housing delimiting an opening of the waveguide, the opening extending around an axis passing through the transducer. The opening may have a radial distance from the axis that varies with an azimuthal angle about the axis. An acoustic path length within the waveguide, between the transducer and the opening, is substantially constant and independent of azimuthal angle about the axis.