Active Acoustic Meta Material Loudspeaker System
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Solution Overview
Problem
Loudspeakers face challenges in achieving optimal sound fidelity, particularly in the far field, due to impedance mismatch between the diaphragm and air, leading to inefficient low-frequency sound reproduction and directional radiation issues, which are exacerbated in compact consumer devices.
Innovation Solution
The use of a torus-shaped acoustic meta material structure with micro-perforated sheets and insulation layers, where higher frequencies are directed through a diaphragm and lower frequencies are outputted transverse to the diaphragm by piezoelectric transducers, creating a matched impedance to amplify and focus pressure waves, allowing for improved sound radiation efficiency across a broadband frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single loudspeaker driver is used to cover the entire audible frequency range, then device complexity is reduced, but sound fidelity and radiation efficiency deteriorate due to incompatible requirements for low and high frequency reproduction
Solution Approach 1:
The invention segments the frequency range by using a passive radiator that naturally resonates at low frequencies while a tweeter handles high frequencies. This segmentation allows each component to specialize in its optimal frequency range, improving overall sound fidelity without requiring multiple active drivers for every frequency band.
Solution Approach 2:
The passive radiator acts as an intermediary element that converts acoustic energy from the tweeter into low frequency sound waves. It mediates between the high frequency tweeter output and the desired low frequency bass response, enabling a single-driver system to produce both high and low frequencies effectively.
2Ease of operation
If the loudspeaker aperture faces the audience directly, then directional sound radiation is improved, but low frequency reproduction deteriorates due to diffraction effects that bend sound around corners
Solution Approach 1:
The passive radiator utilizes mechanical vibration and resonance to produce low frequency sound waves. By designing the passive radiator with appropriate mass, compliance, and damping characteristics, it resonates at low frequencies to generate bass sound that is not affected by diffraction, complementing the directional high frequency output from the tweeter.
3Ease of manufacture
If there is a large impedance mismatch between the diaphragm and air, then manufacturing simplicity is maintained, but sound radiation efficiency deteriorates particularly at low frequencies
Solution Approach 1:
The passive radiator serves as an acoustic intermediary that improves impedance matching between the tweeter and air at low frequencies. It transforms the high frequency acoustic energy from the tweeter into low frequency pressure waves that radiate more efficiently into the air, reducing energy loss and improving radiation efficiency without complicating the manufacturing process.
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 enhances sound amplification and radiation efficiency, particularly in the low-frequency range, improving acoustic performance and maintaining fidelity even in compact devices by effectively addressing impedance mismatch and directional issues.
Implementation Method 1
a plurality of spaced apart transducers on an external side of the torus (a side opposite the portal) output pressure waves through the at least one micro-perforated sheet
Implementation Method 2
The alternating micro-perforated sheets and insulation material can be arranged in parallel layers, one on top of the other, laid out or rolled into a circle creating a torus shape
Implementation Method 3
Sound in this frequency range can easily bend around corners by diffraction (as low frequencies are 'non-directional')
Data Source
AI summary
An active acoustic meta material system with micro-perforated sheets embedded between porous layers and air gaps, around the output region in front of a speaker, perpendicular to the direction of wave propagation of the sound is disclosed. Sound input is split into two frequency ranges by an active controller, such that a higher frequency range is sent to a traditional speaker which outputs sound via a diaphragm which vibrates in response to electromagnetic signals generated based on the sound input. The sound waves in the lower frequency range are sent to piezoelectric or other type of motion-creating transducers which are mounted to an outer housing or casing containing a plurality of meta material sheets with insulative layers between each meta material sheet. The combination of meta material sheets and insulation layers are calibrated to focus and amplify the vibrational waves which are outputted by the transducers.