Adaptive Noise Cancellation Feedback Howling Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing noise cancellation systems in personal audio devices often suffer from 'howling' issues when earbuds are pressed tightly against the ear, leading to poor customer experience due to unanticipated frequency responses.
Innovation Solution
An integrated circuit with a feedback path that generates a feedback anti-noise signal, where the signal gain is a function of the ambient microphone signal, combining this with a source audio signal to cancel ambient audio sounds, and incorporating a compressor to attenuate high magnitudes and prevent howling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the earbud is pressed tightly against the user's pinna to improve acoustic seal, then the acoustic isolation is improved, but the speaker response becomes stronger in particular frequency bands causing feedback howling
Solution Approach 1:
The feedback path signal gain is made variable rather than fixed, allowing the system to adapt to different acoustic conditions. The gain adjusts dynamically based on the ambient microphone signal characteristics, enabling the system to maintain effective noise cancellation while preventing feedback howling when the earbud is pressed tightly against the pinna.
Solution Approach 2:
The system uses a feedback path that monitors the error microphone signal and adjusts the anti-noise signal accordingly. By making the feedback path gain a function of the ambient microphone signal, the system creates a closed-loop control mechanism that automatically prevents feedback howling while maintaining acoustic seal effectiveness.
2Reliability
If the feedback path signal gain is increased to improve noise cancellation effectiveness, then the anti-noise signal strength is improved, but feedback howling is more likely to occur
Solution Approach 1:
The feedback path signal gain is transformed from a static parameter to a dynamic one that varies with ambient noise conditions. This allows the system to increase gain when needed for effective noise cancellation while automatically reducing gain when feedback howling risk increases, resolving the contradiction between effectiveness and stability.
Solution Approach 2:
The system changes the gain parameter of the feedback path based on the ambient microphone signal characteristics. By making gain a function of ambient noise levels and spectral content, the system optimizes noise cancellation effectiveness while preventing feedback howling through adaptive parameter adjustment.
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
Effectively reduces or eliminates howling by adapting the anti-noise signal to the specific acoustic environment and attenuating high-frequency feedback, improving the intelligibility and user experience of audio playback.
Implementation Method 1
a feedback path having a feedback response that generates a feedback anti-noise signal from the error microphone signal
Implementation Method 2
incorporating a compressor to attenuate high magnitudes and prevent howling
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
An integrated circuit may include an output for providing an output signal to a transducer including both a source audio signal for playback to a listener and an anti-noise signal for countering the effect of ambient audio sounds in an acoustic output of the transducer, an ambient microphone input for receiving an ambient microphone signal indicative of the ambient audio sounds; an error microphone input for receiving an error microphone signal indicative of the output of the transducer and the ambient audio sounds at the transducer; and a processing circuit that implements a feedback path having a feedback response that generates a feedback anti-noise signal from the error microphone signal, wherein a signal gain of the feedback path is a function of the ambient microphone signal, and wherein the anti-noise signal comprises at least the feedback anti-noise signal.