Speaker Box Extension Cavity for Acoustic Stability
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Solution Overview
Problem
The reduction in thickness of acoustic structures in mobile devices leads to dynamically varying air space heights in speakers, causing intermodulation distortion, especially at higher frequencies and during playback of certain music types like piano music.
Innovation Solution
A speaker box design incorporating a housing with a sound producing unit, a first damping member covering the sound outlet, and a second damping member defining an extension cavity in communication with the front acoustic cavity, which stabilizes the dynamic frequency response by maintaining a consistent acoustic frequency response across diaphragm positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of the acoustic structure is reduced to meet ultra-thin mobile device requirements, then the device thickness is decreased, but the air space height above the diaphragm becomes insufficient causing dynamically varying cutoff frequency and intermodulation distortion
Solution Approach 1:
The acoustic cavity is segmented into two independent parts: the front acoustic cavity (between diaphragm and cover) and the extension acoustic cavity (formed by damping member and housing). This segmentation allows the extension cavity to provide stable acoustic support while the front cavity maintains its dynamic characteristics for sound production, resolving the contradiction between thin structure and stable frequency response.
Solution Approach 2:
The damping member acts as an intermediary element that introduces the extension acoustic cavity. This intermediary structure provides the necessary acoustic stability and cutoff frequency control without increasing the overall device thickness, as the extension cavity is formed within the existing housing space rather than extending the external dimensions.
2Length of moving object
If the air space height above the diaphragm is reduced to decrease speaker thickness, then the device becomes thinner, but the dynamic variation in air space height causes intermodulation distortion especially at higher frequencies
Solution Approach 1:
By segmenting the acoustic cavity into front and extension portions, the extension cavity provides a stable acoustic reference that does not vary with diaphragm motion. This stable reference reduces the dynamic variation effects that cause intermodulation distortion, while the front cavity maintains the necessary dynamic characteristics for normal speaker operation.
Solution Approach 2:
The invention changes the acoustic parameters by introducing an extension cavity with specific volume and damping characteristics. This alters the overall acoustic impedance and cutoff frequency behavior, providing stable frequency response characteristics even when the front cavity dimensions vary dynamically during operation.
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 design reduces intermodulation distortion and improves sound quality by stabilizing the acoustic frequency response, particularly at higher frequencies and during specific music playback.
Implementation Method 1
a first damping member fixed to the housing and covering the sound outlet, and a second damping member fixed in the receiving space and fixed to the housing
Data Source
AI summary
Provided is a speaker box, which includes a first damping member fixed to the housing and covering the sound outlet, and a second damping member fixed in the receiving space and fixed to the housing. The second damping member, the base and/or the cover define an extension cavity in communication with the front acoustic cavity. When the speaker produces sound, the extension cavity stabilizes frequency response variation caused by variation in the dynamic height of the air space. When the diaphragm of the speaker is at the lowest and highest positions of the air space, the variation in the final acoustic frequency response of the speaker box is always small, and the final acoustic frequency response of the speaker is also small. Thus, the intermodulation distortion of speakers in mobile devices or other thin devices can be reduced, and a sound quality of the speaker box can be improved.