Phase Plug With Variable Area Channels For Acoustic Resonance Control
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Solution Overview
Problem
Compression drivers face acoustic resonance issues due to cavity modes in the small cavity in front of the diaphragm, which affect driver linearity and output, and existing designs fail to adequately address these resonances, particularly at high frequencies.
Innovation Solution
A phase plug design with channels and slots on its input surface, where the areas and widths vary according to a mathematical relationship involving the radial position and angle, specifically proportional to functions like r.cosΦ, to minimize resonance excitation by the diaphragm and air motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the cavity in front of the diaphragm is used to achieve high acoustic load and efficiency, then the compression driver becomes highly efficient, but strong resonances (cavity modes) occur at distinct frequencies causing large pressure response variations
Solution Approach 1:
The phase plug incorporates channels with non-uniform cross-sectional areas along their length, creating different local acoustic properties within the cavity. The channels have smaller cross-sectional areas near the diaphragm and larger areas toward the horn throat, which modifies the acoustic impedance distribution and suppresses cavity mode resonances while preserving the high-frequency response benefits of the closed-cavity compression driver.
2Ease of manufacture
If the channels in the phase plug have uniform width, then the design is simple, but resonances are still excited by diaphragm motion and air flow
Solution Approach 1:
The patent applies parameter changes by varying the cross-sectional area of the phase plug channels along their length. The channels transition from smaller areas near the diaphragm to larger areas at the horn throat, creating a gradual area expansion that suppresses resonance excitation while maintaining manufacturability through controlled geometric progression.
3Object-affected harmful factors
If the channel areas vary according to r.cosΦ relationship, then resonance excitation is minimized, but the manufacturing precision requirements increase
Solution Approach 1:
The phase plug channels are designed with curved, spherical geometries that naturally embody the r.cosΦ area variation relationship. The input surface of the phase plug is spherical, and the channels are arranged radially on this spherical surface, which simplifies the manufacturing process by using standard spherical machining techniques rather than requiring complex precision control of irregular shapes.
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
Significantly reduces or eliminates acoustic resonances between the diaphragm and horn waveguide, improving driver linearity and output consistency across frequencies.
Implementation Method 1
a body including a plurality of channels extending from the input side to the output side for propagating acoustic waves through the body
Implementation Method 2
The cavity is connected by a phase plug (also known as a phase adaptor, a phase transformer, an acoustic transformer, etc.) to an aperture
Data Source
Figure 1
Figure 2
Figure 3(a)~3(f)
AI summary
A phase plug comprises a body having an input side for receiving acoustic waves and an output side for transmitting acoustic waves, the body including a plurality of channels extending from the input side to the output side for propagating acoustic waves through the body. The input side comprises an input surface which includes a plurality of openings constituting entrances for the channels, the input surface being substantially part of a sphere or an ellipsoid in shape. The areas of the openings vary with radial position on the input surface, the radial position being measured in a direction extending perpendicularly from a central axis extending through the input surface. The variation in the areas is a function of the cosine of an angle subtended at the centre of the sphere or a focus of the ellipsoid between the central axis and the radial position.