In-Ear Headphone Control Leak and ANC Tuning
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Solution Overview
Problem
In-ear headphones with acoustic sealing cause the occlusion effect, leading to increased low-frequency sound pressure, which existing pressure vents may not effectively alleviate due to user variability in ear canal shape and size, and can reduce passive noise attenuation.
Innovation Solution
Incorporating a control leak and feedback acoustic noise cancellation (ANC) system in in-ear headphones, where a microphone signal is used to determine an ANC filter, generating an anti-noise signal to reduce sound pressure levels within the ear canal, thereby minimizing the occlusion effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If acoustic sealing is used in in-ear headphones to isolate ambient noise, then passive noise attenuation is improved, but the occlusion effect increases causing higher low-frequency sound pressure in the ear canal
Solution Approach 1:
The patent extracts the harmful low-frequency sound pressure from the ear canal by introducing a control leak that creates an acoustic path from the ear canal to the ambient environment. This allows the trapped air pocket to vent, reducing the occlusion effect while maintaining the acoustic seal for ambient noise isolation.
Solution Approach 2:
The patent applies preliminary anti-action by using a feedback ANC system that generates anti-noise signals in advance to counteract the occlusion effect. The system continuously monitors the sound pressure in the ear canal and generates opposing acoustic signals to reduce the low-frequency pressure buildup before it becomes problematic.
2Object-generated harmful factors
If pressure vents are introduced to reduce the occlusion effect, then sound pressure in the ear canal is reduced, but passive noise attenuation is compromised
Solution Approach 1:
The patent applies local quality by creating a controlled acoustic leak at a specific location within the headphone structure, rather than using a general pressure vent. This localized control leak is designed to specifically target low-frequency pressure relief while maintaining the overall acoustic seal integrity for ambient noise isolation.
Solution Approach 2:
The patent uses a feedback mechanism where a microphone monitors the sound pressure level in the ear canal and the system dynamically adjusts the ANC output to maintain optimal pressure control. This feedback loop ensures that the control leak and ANC work together to reduce occlusion without compromising noise attenuation.
3Object-generated harmful factors
If feedback ANC is applied to reduce sound pressure in the ear canal, then the occlusion effect is minimized, but system complexity increases
Solution Approach 1:
The patent applies self-service by designing the feedback ANC system to automatically adapt to individual user ear canal characteristics. The system performs self-tuning by analyzing the microphone signal and automatically adjusting the ANC filter parameters, eliminating the need for manual calibration or complex user setup procedures.
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 combination of the control leak and ANC effectively reduces sound pressure levels in the ear canal, alleviating the occlusion effect by up to 25 dB across specific frequency ranges, improving user experience by minimizing perceived echo-like sounds.
Implementation Method 1
the control leak is a path from the in-ear headphone into an ambient environment in which the in-ear headphone is located
Implementation Method 2
the system applies acoustic noise cancellation (ANC) to reduce the SPL in the ear canal of the user
Data Source
AI summary
A method performed by an in-ear headphone that includes a speaker and an internal microphone. The method receives a microphone signal from the internal microphone that indicates a current sound pressure level (SPL) in an ear canal of a user. The current SPL is a result of a control leak from the in-ear headphone into an ambient environment that reduces a SPL in the ear canal between 2 dB and 25 dB at a frequency within a frequency range than if otherwise not present. The method determines an active noise cancellation (ANC) filter based on the microphone signal and generates an anti-noise signal using the ANC filter. The method drives the speaker using the anti-noise signal to reduce the current SPL in the ear canal of the user as much as 25 dB at a frequency within the frequency range.