Earphone Transducer Arrays for Accurate Sound Localization
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Solution Overview
Problem
Conventional headphones fail to eliminate in-the-head localization of sound images and exhibit poor center images in a stereo panorama due to their design, which obstructs rear sound rendering and requires diffuse-field equalization.
Innovation Solution
The earphone design features a low-frequency loudspeaker at the bottom wall and a front array of high-frequency loudspeakers on the sidewall, with both types of speakers configured to radiate sound into a sound-absorbing chamber, allowing for accurate pinna interaction and improved timbre and sound quality, optionally including a rear array for surround sound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multiple transducers are built into or in the proximity of the main baffle, then front sound rendering is improved, but rear sound becomes difficult to render because transducers are located behind the pinna and are obstructed
Solution Approach 1:
The patent divides the transducer system into multiple arrays positioned at different locations: a first array on the front surface for front sound, a second array on the rear surface for rear sound, and a third array on the side surface for side sound. This segmentation allows each array to be optimally positioned for its specific sound direction without obstruction, resolving the contradiction between front sound rendering and rear sound accessibility.
Solution Approach 2:
The patent transitions from a single-plane transducer arrangement to a three-dimensional distribution of transducer arrays across multiple surfaces (front, rear, and side) of the housing. This spatial dimensionality change enables sound radiation in multiple directions simultaneously, eliminating the obstruction problem for rear sound while maintaining front sound quality.
2Adaptability or versatility
If conventional headphones use a single large loudspeaker aiming at acoustically bypassing the pinna, then diffuse-field equalization can be applied, but in-the-head localization of sound images cannot be eliminated and center images are poor
Solution Approach 1:
The patent applies different acoustic characteristics to different regions of the housing by positioning transducer arrays at specific locations (front, rear, side) with different orientations and radiation patterns. Each array is locally optimized for its directional sound radiation, enabling precise control over sound image localization and center imaging while maintaining compatibility with diffuse-field equalization through the cup-shaped housing design.
3Volume of moving object
If transducers are located behind the pinna, then compact housing is achieved, but rear sound is obstructed and timbral distortion increases
Solution Approach 1:
The patent segments the transducer functionality across multiple arrays positioned on different surfaces of the compact cup-shaped housing. The second array is specifically positioned on the rear surface to radiate rear sound without obstruction, while the first and third arrays handle front and side sound respectively. This segmentation maintains compact housing while eliminating the obstruction problem.
Solution Approach 2:
The cup-shaped housing acts as an acoustic intermediary that channels and directs sound waves from the rear array toward the ear canal. The housing structure mediates between the compact placement requirement and the rear sound radiation requirement, enabling sound to reach the ear without obstruction while maintaining a compact form factor.
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 enables accurate out-of-the-head localization of sound images and rich center images in a stereo panorama by using a binaural, head-related target function, reducing unwanted reflections and enhancing sound quality through personalized head-related transfer function adjustments.
Implementation Method 1
The bottom wall and the sidewall are made from or comprise sound absorbing material adjacent to the chamber
Data Source
Figure 1a~1c
Figure 2~4
Figure 5~6
AI summary
An earphone includes a housing having a cup-like shape and comprising a bottom wall and a circumferential sidewall, the bottom wall and the sidewall encompassing an open chamber, the chamber being closed when the earphone is worn over an ear of a user. The earphone further includes a low-frequency loudspeaker mounted to the bottom wall and configured to radiate low-frequency sound into the chamber, and a front array of at least three high frequency loudspeakers mounted to the sidewall and configured to radiate high-frequency sound into the chamber, the front array being disposed adjacent to the rostral end of the ear when the earphone is worn over the ear of the user. The bottom wall and the sidewall are made from or comprise sound absorbing material adjacent to the chamber. The low-frequency loudspeaker and the high-frequency loudspeakers are configured to receive one electrical signal to be acoustically reproduced. A headphone includes two such earphones, each earphone being supplied with at least one signal to be reproduced.