ANR Headphone Interface with Dynamic Hear-Through Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing active noise reduction (ANR) headphones fail to provide natural hear-through of ambient sounds while maintaining effective noise cancellation, often resulting in an artificial or muddled auditory experience due to the occlusion effect and limited frequency response.
Innovation Solution
The implementation of a sophisticated active noise reduction system with feed-forward and feedback microphones and signal processors that apply specific filters and gain control to achieve natural hear-through by modifying the active noise cancellation parameters, allowing controlled ambient sound to pass through with reduced cancellation, and compensating for sound changes caused by passive attenuation across the full range of audio frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active noise cancellation is applied to block ambient noise, then noise reduction is improved, but the ability to hear ambient sounds naturally deteriorates
Solution Approach 1:
The patent implements dynamic switching between noise cancellation mode and hear-through mode, allowing the system to adapt its noise reduction characteristics based on user needs. The signal processor can transition between applying full noise cancellation filters and reduced cancellation filters that allow ambient sounds to pass through more naturally, resolving the contradiction between effective noise blocking and natural ambient sound perception.
Solution Approach 2:
The system changes the parameters of the noise cancellation filters dynamically. In hear-through mode, the signal processor applies modified filter parameters that reduce the cancellation effect in certain frequency ranges, allowing ambient sounds to be heard more naturally while still maintaining some level of noise reduction. This parameter adjustment resolves the contradiction by making the noise cancellation effectiveness variable rather than fixed.
2Ease of operation
If talk-through feature is implemented using external microphones and speakers, then ambient sound reproduction is improved, but the naturalness of ambient sound deteriorates due to artificial reproduction
Solution Approach 1:
Instead of using external microphones to capture and reproduce ambient sounds (talk-through approach), the patent extracts and utilizes the ambient sounds that are already present in the acoustic volume inside the ear cup. The feedback microphone captures these naturally occurring ambient sounds, and the signal processor enhances them while removing the artificial reproduction chain, thereby preserving ambient sound naturalness while still providing ambient sound reproduction capability.
3Ease of operation
If passive monitoring is used to allow ambient sounds to pass through, then ambient sound perception is improved, but noise cancellation effectiveness deteriorates
Solution Approach 1:
The patent applies partial noise cancellation rather than complete cancellation. The signal processor reduces the noise cancellation effect in specific frequency ranges where ambient sounds are important for natural perception, while maintaining stronger cancellation in other frequency ranges. This partial application of noise cancellation allows ambient sounds to be heard more naturally without completely sacrificing noise reduction effectiveness, resolving the contradiction through selective rather than universal cancellation.
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 solution enables users to hear ambient sounds naturally, reduces the occlusion effect, and maintains effective noise cancellation, providing a seamless transition between noise reduction and hear-through modes with improved situational awareness and audio content enjoyment.
Implementation Method 1
electronic circuits are used to generate anti-noise signals that destructively interfere with ambient sound to cancel it
Implementation Method 2
an output transducer acoustically coupled to the acoustic volume via the volume within the ear cup
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
An active noise reducing headphone has an active noise-cancelling mode and an active hear-through mode, and changes between the noise-cancelling mode and the hear-through mode based on detection of a user touching a housing of the headphone or based on a command signal received from an external device. In another aspect, a signal processor in the headphone is configured to change between the active noise-cancelling and active hear-through modes based on a comparison of signals from a feed-forward microphone and a feedback microphone. During the hear-through mode, the signal processor detects high-frequency signals in the feed-forward path exceeding a threshold level indicative of abnormally high acoustic coupling of the output transducer to the feed-forward microphone, and applies a compressing limiter to the feed-forward path until the high-frequency signals are no longer detected at levels above the threshold.