Bass-Reflex Speaker Port Geometry for Stable Low-Frequency Sound
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Solution Overview
Problem
Conventional speaker devices in chairs, such as those described in JP 2007-221485 A, suffer from varying sound pressure levels of low-pitched sounds due to changes in the listener's sitting height or posture, leading to inconsistent audio quality.
Innovation Solution
The acoustic device features a case with speaker units and bass-reflex ports or passive vibrating bodies oriented to maintain consistent sound pressure levels by elongating openings in the up-down direction, ensuring balanced sound delivery regardless of ear position changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional circular bass-reflex port is used, then the speaker structure is simple, but the sound pressure level of low-pitched sounds varies greatly when the listener's ear position changes
Solution Approach 1:
The bass-reflex port is changed from a circular shape to an elliptical shape with the longer axis in the up-down direction. This dimensional change in the port geometry allows the sound waves to be directed more effectively toward the listener's ear regardless of slight position changes, thereby improving sound pressure level consistency without complicating the overall structure.
Solution Approach 2:
The opening dimensions of the bass-reflex port are specifically designed with the up-down direction dimension being larger than the horizontal direction dimension. This parameter change in the port's geometric dimensions optimizes the acoustic output directionality to match the typical orientation of the human ear, ensuring consistent low-pitched sound pressure levels across varying ear positions.
2Reliability
If the duct opening area is small, then the speaker unit structure is compact, but the sound pressure level of low-pitched sounds varies with listener position
Solution Approach 1:
The duct opening is transformed from a circular cross-section to an elliptical cross-section with the major axis oriented in the up-down direction. This dimensional transformation allows the opening to cover a greater vertical range, better matching the vertical position of the human ear, thereby maintaining consistent sound pressure levels without significantly increasing the overall opening area.
3Reliability
If the bass-reflex port opening in the up-down direction is enlarged, then sound pressure level consistency is improved, but the horizontal opening dimension is reduced
Solution Approach 1:
The bass-reflex port is designed with non-uniform dimensions in different directions, specifically making the up-down dimension larger than the horizontal dimension. This local quality differentiation optimizes the port's performance for the specific application of directing sound toward the human ear, where vertical positioning is more critical than horizontal positioning, thereby achieving sound pressure consistency without unnecessarily reducing horizontal 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 device provides stable and enhanced low-pitched sound pressure levels by maintaining a balanced acoustic effect across varying ear positions, ensuring consistent audio quality even with changes in sitting height or posture.
Implementation Method 1
a bass-reflex port that communicates with the air chamber and is open in the forward direction
Implementation Method 2
air vibration on the rear side of the speaker unit is transmitted
Data Source
AI summary
A speaker unit on the left side and a speaker unit on the right side are included in a case positioned behind a listener. Sound generation openings and bass-reflex ports are formed in the case on the left side and right side. From each sound generation opening, sound pressure generated forward by the relevant speaker unit is output. Each bass-reflex port communicates with an air chamber to which sound pressure behind the speaker unit is transmitted. With each sound generation opening, the opening dimension in the up-down direction is larger than the opening dimension in the horizontal direction. With each bass-reflex port, as well, the opening dimension in the up-down direction is larger than the opening dimension in the horizontal direction.