Directional Loudspeaker Mid-Range Back Wave Attenuation
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Solution Overview
Problem
Conventional loudspeakers exhibit frequency-dependent directivity, leading to undesirable omni-directional sound radiation in the mid frequency range, which affects sound quality and noise pollution, with existing solutions failing to achieve high directivity and sufficient attenuation of back waves in this range.
Innovation Solution
A directional loudspeaker design featuring a housing with a front panel, side panels, and a reflective back panel filled with acoustic resistive material and openings that introduce phase delay and attenuation to mid frequency range sound waves, achieving at least 20 dB attenuation at the backside, using fibrous thermoplastic polymer materials and optimized geometry to maximize cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional loudspeaker design is used, then omnidirectional sound radiation occurs in mid frequency range, but this causes poor sound quality and high noise pollution
Solution Approach 1:
The loudspeaker system is segmented into multiple frequency ranges (low, mid, high) with dedicated transducers for each range. The mid-range transducer is specifically designed with directional control features to segment the sound radiation pattern by frequency, allowing omnidirectional low-frequency radiation while directing mid and high frequencies forward to improve sound quality and reduce noise pollution.
Solution Approach 2:
Different parts of the loudspeaker system have different radiation characteristics tailored to their frequency range. The mid-range and high-frequency transducers are positioned and oriented to provide directional sound radiation forward, while low-frequency transducers maintain omnidirectional radiation. This local differentiation of radiation quality improves overall sound quality and reduces backward noise pollution.
2Ease of operation
If waveguide is used for high-frequency directionality, then directional control is achieved, but waveguides are too large for mid frequency range
Solution Approach 1:
The patent changes the approach to directional control based on frequency parameters. For mid-range frequencies where waveguides would be too large, the invention uses a combination of transducer orientation, positioning relative to the housing, and electronic signal processing to achieve directional control without requiring large physical waveguide structures.
Solution Approach 2:
The patent replaces the mechanical waveguide system with alternative methods for mid-range directional control, including strategic transducer placement, housing geometry design, and electronic beam forming techniques, thereby achieving directionality without the bulky mechanical structures required by traditional waveguides.
3Object-generated harmful factors
If cardioid subwoofer configuration is used for low-frequency directionality, then backward radiation is reduced, but the technique is ineffective for mid frequency range
Solution Approach 1:
The loudspeaker system segments the frequency ranges and applies different directional control techniques to each segment. Low-frequency transducers use cardioid or figure-8 configurations to reduce backward radiation, while mid-range transducers use forward-facing orientation and positioning. This segmentation allows each frequency range to be optimized independently for directional control.
Solution Approach 2:
The housing design incorporates universal features that support multiple directional control strategies across different frequency ranges. The housing geometry, transducer mounting structures, and acoustic pathways are designed to accommodate both low-frequency cardioid configurations and mid-range directional radiation patterns, making the system adaptable across the full audio spectrum.
4Device complexity
If frequency-dependent directivity is accepted, then simple loudspeaker design is maintained, but sound levels vary significantly across frequency ranges
Solution Approach 1:
The patent applies local quality by giving different radiation characteristics to different frequency ranges. Low-frequency transducers are designed for omnidirectional radiation to provide consistent bass response throughout the room, while mid-range and high-frequency transducers are oriented for directional forward radiation to ensure consistent mid and high-frequency sound levels in the listening area, compensating for the natural frequency-dependent directivity of simple loudspeaker designs.
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 forward bundling of sound waves in the mid frequency range while significantly attenuating back waves, enhancing sound quality and comprehensibility, and maintaining consistent tonal balance across the audible spectrum.
Implementation Method 1
a housing (101) comprising a front panel, side panels and a reflective back panel, said housing comprising an acoustic resistive material; wherein at least one acoustic transducer is mounted to said front panel, said transducer being configured to drive a membrane for producing front waves at the front of said membrane and back waves at the back of said membrane; and, wherein one or more openings in said side panels, and, optionally, in said back panel allowing at least part of said back waves to exit said housing via said resistive material
Implementation Method 2
one or more openings in said side panels, and, optionally, in said back panel allowing at least part of said back waves to exit said housing via said resistive material, said resistive material, said openings and said reflective back panel introducing for said back waves in the mid frequency range a phase delay, an attenuation and an amplitude
Implementation Method 3
said transducer being configured to drive a membrane for producing front waves at the front of said membrane and back waves at the back of said membrane
Data Source
Figure 1A~1B
Figure 2
Figure 3(A)~3(D)
AI summary
A directional loudspeaker is described for use in the mid frequency range of the audio spectrum. The loudspeaker comprises: a housing comprising a front panel, side panels and a back panel, said housing comprising an acoustic resistive material; wherein at least one acoustic transducer is mounted to said front panel, said transducer being configured to drive a membrane for producing front waves at the front of said membrane and back waves at the back of said membrane; and, wherein one or more openings in said side panels, and, optionally, in said back panel allowing at least part of said back waves to exit said housing via said resistive material, said resistive material, said openings and said reflective back panel introducing for said back waves in the mid frequency range a phase delay, an attenuation and an amplitude such that an attenuation at the backside of said loudspeaker of 15 dB or more of the mid range frequencies is achieved.