Noise-Cancelling Headphone Baffle Layout for Feedback Suppression
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Solution Overview
Problem
Conventional noise-cancelling headphones using feedback noise cancellation technology face issues with acoustic feedback in the high-frequency band due to sound waves being fed back and enhanced, while also degrading low-frequency reproduction output.
Innovation Solution
A noise-cancelling headphone device with a speaker unit featuring a center dome and sub-dome diaphragm, where an acoustic resistance member is placed only on the baffle plate facing the sub-dome to attenuate high-frequency sound, while allowing low-frequency sound to pass unattenuated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an acoustic resistance member is placed between the front cavity and the entire area of the diaphragm's sound emitting surface to suppress acoustic feedback, then acoustic feedback is reduced, but the audio output in the low-frequency band is attenuated, degrading reproduction frequency characteristics
Solution Approach 1:
The acoustic resistance member is placed only in the area facing the sub-dome of the diaphragm, not covering the entire sound emitting surface. This local placement allows selective attenuation of high-frequency sound waves generated by the sub-dome while leaving low-frequency reproduction from the center dome unaffected, thus suppressing acoustic feedback without degrading overall reproduction frequency characteristics
Solution Approach 2:
The diaphragm is divided into a center dome and a sub-dome, and the acoustic resistance member is selectively placed only in front of the sub-dome. This segmentation approach allows different parts of the diaphragm to have different acoustic treatments applied to them, targeting the specific source of high-frequency feedback while preserving low-frequency output
2Measurement precision
If the microphone is placed near the diaphragm to collect noise components, then noise collection is improved, but high-frequency sound waves are also collected and fed back through the noise cancellation circuit, causing acoustic feedback
Solution Approach 1:
The acoustic resistance member is selectively placed only in the area facing the sub-dome to attenuate high-frequency sound waves before they reach the microphone. This local treatment allows the microphone to continue collecting low-frequency noise components effectively while blocking the high-frequency sound waves that would otherwise be fed back and cause acoustic feedback
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 effectively suppresses acoustic feedback in the high-frequency band while maintaining good reproduction characteristics in the low-frequency band, ensuring balanced frequency response across the entire bandwidth.
Implementation Method 1
an acoustic resistance member is provided only in an area of the baffle plate on the sound emitting side of the diaphragm that radiates reproduction sound and that faces the sub-dome of the diaphragm
Data Source
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AI summary
Provided is a noise-cancelling headphone device that prevents deterioration of reproduction frequency characteristics in a high-frequency band while preventing reduction in the reproduction output in the low-frequency band. The proposed technology is a noise-cancelling headphone device, including a speaker unit 4 provided with a dome-shaped diaphragm 2 having a center dome 5 and a sub-dome 6, a microphone 31 that detects ambient noise incident into the speaker unit, a baffle plate 17 supporting the speaker unit and provided with sound emission holes 20, 22 to radiate reproduction sound emitted from the speaker unit, and a signal processing circuit to generate noise cancellation signal generated based on the ambient noise detected by the microphone, wherein an acoustic resistance member 35 is provided at the position facing the sub-dome 6 of the dome diaphragm.