Omnidirectional Sound Source Using Spherical Baffle Diffraction
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Solution Overview
Problem
Current sound sources, including expensive audiophile loudspeakers, fail to provide an omnidirectional sound radiation pattern uniformly across all directions and frequencies, making them unsuitable for acoustical measurements and other applications that require consistent sound distribution.
Innovation Solution
A low-profile, axi-symmetrical, downward-curving convex baffle with a small orifice at its apex houses a loudspeaker, ensuring sound waves radiate omnidirectionally through the orifice, while internal damping materials and sound-absorbing materials prevent vibration and rear sound wave interference, maintaining a consistent sound field across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional loudspeakers are used, then sound can be produced with sufficient amplitude, but the sound radiation pattern is not omnidirectional and varies by direction
Solution Approach 1:
The patent employs a spherical baffle geometry with a small aperture at its center. The spherical shape ensures that sound waves radiate uniformly in all directions (omnidirectionally) from the aperture, eliminating directional preferences inherent in traditional planar loudspeaker designs. This curvature principle directly resolves the contradiction by making the radiation pattern omnidirectional while maintaining uniform sound distribution throughout the space.
2Productivity
If a single sound source is used to cover the entire frequency range, then test time is reduced, but achieving omnidirectional radiation across all frequencies is difficult
Solution Approach 1:
The patent utilizes the aperture diameter-to-wavelength ratio as a critical parameter. By making the aperture sufficiently small relative to the wavelength across the entire frequency range of interest, the system maintains omnidirectional radiation characteristics from 100 Hz to 10 kHz. This parameter control allows a single sound source to achieve broad frequency coverage while preserving omnidirectional behavior, thereby reducing test time without sacrificing measurement reliability.
3Power
If the aperture is made larger to increase sound amplitude, then loudness improves, but omnidirectional radiation pattern degrades
Solution Approach 1:
The spherical baffle acts as an intermediary structure that couples the loudspeaker driver to the surrounding space. The small aperture in the sphere serves as a controlled interface that transforms the directional output of the loudspeaker into omnidirectional radiation. This intermediary structure allows the system to achieve sufficient sound amplitude through the aperture while maintaining the omnidirectional radiation pattern, as the spherical geometry and small aperture size work together to distribute sound energy uniformly in all directions.
4Reliability
If multiple sound sources are used to achieve omnidirectional coverage, then radiation pattern improves, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for multiple loudspeaker drivers by using a single driver coupled with a spherical baffle structure. The omnidirectional radiation pattern is achieved not through multiple sources but through the geometric properties of the single source's enclosure. This extraction of the spherical baffle concept from traditional multi-driver designs simplifies the device to a single sound source while maintaining reliable omnidirectional coverage across the frequency range.
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 provides a reliable, omnidirectional sound source with sufficient amplitude across 100-10,000 Hz, meeting signal-to-noise standards and ensuring consistent sound levels in all directions, effectively addressing the limitations of existing sound sources.
Implementation Method 1
A low-profile baffle is formed as a bounded, axi-symmetrical, downward-curving convex 'cap' or dome... with an orifice located at its apex... configured for directing sound waves at the orifice and through the orifice
Implementation Method 2
The volume of the enclosure below the loudspeaker and mounting ring or plate is filled with sound-absorbing material to effectively absorb any sound radiating from the rear of the loudspeaker
Implementation Method 3
The curved baffle is treated with either an internal damping material (e.g., a 'damped metal' or 'constrained layer damping') or an attached damping material (e.g., 'extensional damping') to limit its vibration
Data Source
AI summary
An omnidirectional sound source is formed by mounting a loudspeaker in an enclosed baffle, preferably formed as a low profile hemi-spherical, convex cap with a small circular orifice at its apex and a planar base. The loudspeaker is mounted within the baffle, affixed to the underside of the baffle cap directly beneath the orifice. Substantially plane audio-frequency wavefronts emanating from the immediate vicinity of the loudspeaker diaphragm pass through the orifice and, by the process of diffraction emerge as spherical waves. The spherical wavefronts follow the smooth, axisymmetric, gently curved contour of the low-profile, hemispherical baffle and are not distorted by edge effects where the baffle joins its planar base. As a result, an omnidirectional sound source is obtained.