Earphone Feedback Microphone Rear-Side Diaphragm Placement
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Solution Overview
Problem
Feedback active noise cancellation systems in headphones face challenges in placing microphones close to the speaker diaphragm to effectively cancel noise, especially at higher frequencies due to phase shift and displacement issues.
Innovation Solution
The microphone is positioned within a short distance (less than 5 mm) behind the diaphragm, using a MEMS-type microphone on a flexible printed circuit board, which is protected and positioned to minimize phase shift, allowing efficient noise cancellation at higher frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the feedback microphone is placed close to the speaker diaphragm to reduce phase shift for high frequency noise cancellation, then the active noise cancellation effectiveness at higher frequencies is improved, but the microphone becomes vulnerable to external forces and displacement
Solution Approach 1:
The patent positions the feedback microphone on the rear side of the diaphragm (behind it) rather than in front, creating a protected spatial arrangement. The microphone opening faces the rear side of the diaphragm through a microphone channel, placing the microphone in a dimensionally different location that is shielded from external forces while maintaining acoustic coupling for effective noise cancellation.
Solution Approach 2:
The feedback microphone is nested within the speaker assembly structure, specifically positioned behind the diaphragm and integrated into the housing. This nested arrangement protects the microphone while maintaining its functional proximity to the diaphragm for accurate noise feedback.
2Measurement precision
If the distance between the microphone opening and the rear side of the diaphragm is reduced to minimize phase shift, then the active noise cancellation performance at higher frequencies is improved, but the microphone may be inadvertently displaced by external forces
Solution Approach 1:
The microphone is positioned in the rear dimension behind the diaphragm rather than in the front acoustic chamber. This dimensional repositioning allows the microphone opening to be placed within 5mm of the diaphragm rear side for minimal phase shift, while the diaphragm itself acts as a protective barrier against external forces.
3Measurement precision
If the feedback microphone is arranged closer to the centre axis to capture the acoustic field more effectively, then the noise cancellation accuracy is improved, but the microphone becomes more exposed to external forces and displacement
Solution Approach 1:
The patent positions the microphone on the rear side of the diaphragm, offset from the center axis, facing the rear side through a microphone channel. This rear-side positioning captures the acoustic field effectively while the diaphragm structure shields the microphone from external forces that would affect a front-side or center-axis placement.
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 effective active noise cancellation at higher frequencies while protecting the microphone from external forces, ensuring reliable performance.
Implementation Method 1
a feedback microphone (9) arranged at the rear-side of a speaker diaphragm (4), wherein the feedback microphone (9) is adapted to pick up sound in the frequency range of 20 Hz to 20 kHz
Implementation Method 2
a speaker unit (3) comprising a speaker diaphragm (4), a voice coil (12) and a magnetic circuit unit (25)
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
An earphone (1) comprising an earphone housing (2), a speaker unit (3), the speaker unit (3) comprising a diaphragm (4). A front chamber (29) is defined in the earphone between a front side (31) of the diaphragm (4) and the user (7), when the earphone (1) is worn. A rear chamber (27) is defined between the earphone housing (2) and a rear side (32) of the diaphragm (4). The earphone (1) comprises an active noise cancelling feedback microphone (9), which is arranged in the rear chamber (27) and which comprises a microphone opening (11). The distance (D) between the microphone opening (11) and the rear side (32) of the diaphragm (4) is less than 5 mm. The invention also relates to the assembly of an earphone with an active noise cancelling feedback microphone arranged at the rear-side of a speaker diaphragm.