Headrest Speaker Enclosure With Acoustic Absorption for Standing Waves
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Solution Overview
Problem
Acoustic enclosures in headrests suffer from uncontrolled sound reflections and emissions due to their limited geometry, leading to variations in sound pressure levels and total harmonic distortion, resulting in degraded sound quality.
Innovation Solution
Incorporating a layer of acoustic absorbent material inside the cavity of the acoustic enclosure, specifically covering the bottom part, to absorb sound waves and reduce reflections, thereby minimizing standing waves and improving sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the acoustic enclosure is integrated into the headrest with limited dimensions, then the headrest can accommodate the speaker system, but the cavity geometry creates uncontrolled sound reflections and standing waves
Solution Approach 1:
The patent applies porous acoustic absorbent material (such as foam or fibrous material) to the internal walls of the cavity. This porous structure allows sound waves to enter the material where friction and viscous forces convert acoustic energy into heat, effectively absorbing the sound energy and preventing reflections and standing waves while working within the limited cavity volume.
Solution Approach 2:
The acoustic absorbent material acts as an intermediary between the sound waves and the cavity walls. Instead of sound waves directly reflecting off the hard cavity surfaces, the absorbent material intercepts these waves and dissipates their energy, mediating the interaction to eliminate harmful reflections.
2Object-generated harmful factors
If traditional acoustic speaker geometry is used, then optimal sound wave propagation is achieved, but the headrest integration and limited space are compromised
Solution Approach 1:
The patent applies acoustic absorbent material specifically to the bottom part and selected zones of the cavity walls rather than uniformly throughout. This localized treatment targets the specific areas where reflections and standing waves are generated, allowing optimal sound propagation in other regions while maintaining headrest integration constraints.
3Length of stationary object
If the cavity has limited volume for headrest integration, then the headrest dimensions are maintained, but sound pressure variations and harmonic distortion increase
Solution Approach 1:
The patent converts the potentially harmful effect of limited cavity volume, which causes standing waves and distortion, into a benefit by strategically placing acoustic absorbent material. This material transforms the problematic reflections into absorbed energy, and in some configurations, the absorbent material itself becomes part of the acoustic path to enhance sound quality within the constrained space.
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 use of acoustic absorbent material enhances sound quality by reducing distortions and reflections, providing better sound emission and increased external insulation, while virtually increasing the cavity volume to lower cut-off frequencies.
Implementation Method 1
The layer of acoustic absorbing material arranged inside the cavity has the effect of absorbing the energy of the sound waves emitted by the speaker
Implementation Method 2
the layer of acoustic absorbing material improves insulation from the exterior of the acoustic enclosure by reducing vibrations and radiation from the box
Data Source
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AI summary
The invention relates to a headrest comprising at least one acoustic enclosure (24A), the acoustic enclosure (24A) comprising: - at least one loudspeaker (30A) defining a loudspeaker axis (X), configured to emit sound waves, - a box comprising at least one internal wall (42) delimiting with the loudspeaker (30A) a cavity (40), the internal wall (42) having at least one receiving part (48) of the loudspeaker (30A) delimiting an opening (51) and a bottom part (50) opposite the receiving part (48) along the loudspeaker axis (X), the loudspeaker (30A) being mounted on at least one edge of said opening (51). According to the invention, the acoustic enclosure (24A) comprises at least one layer (38) of at least one acoustic absorbing material arranged inside the cavity (40) and covering at least one cover zone (52) of the bottom part (50).