Vehicle Cabin Audio Feedback Cancellation Using Shared Adaptive Filtering
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Solution Overview
Problem
Existing communication support systems in vehicles face excessive system size and processing volume due to the need for additional adaptive filters to prevent audio feedback when performing active noise control and echo cancellation, leading to inefficiencies in suppressing audio feedback.
Innovation Solution
A communication support system that incorporates a noise canceling adaptive filter and an audio feedback canceling section, using a transfer function update processing section to adapt and update filter coefficients, thereby canceling audio feedback without a dedicated adaptive filter, by applying a transfer function equivalent to the noise canceling adaptive filter's operation to the sound source output sound signal and adding the second area sound signal to the first area speaker's output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated adaptive filter is added to cancel audio feedback, then audio feedback suppression is improved, but system size and processing volume increase excessively
Solution Approach 1:
The patent makes the existing noise canceling adaptive filter perform dual functions: it continues to cancel noise from sound source output while simultaneously canceling audio feedback by applying the transfer function of the second area speaker to the first area microphone input. This eliminates the need for a dedicated third adaptive filter for feedback cancellation, resolving the contradiction between feedback suppression effectiveness and system complexity.
Solution Approach 2:
The patent merges the audio feedback cancellation function with the existing noise canceling adaptive filter by adding a transfer function processing path. The filter now processes both noise cancellation and feedback cancellation through unified signal processing, combining multiple functions into a single device to reduce overall system complexity while maintaining effective feedback suppression.
2Reliability
If a dedicated adaptive filter is added to cancel audio feedback, then audio feedback suppression is improved, but processing volume increases excessively
Solution Approach 1:
The existing noise canceling adaptive filter is made universal to handle both noise cancellation and audio feedback cancellation tasks. By applying the transfer function of the second area speaker to the first area microphone signal path, the same filter processing resources are utilized for dual purposes, avoiding the additional processing burden that would result from a dedicated third adaptive filter.
Solution Approach 2:
The patent changes the operational parameters of the existing adaptive filter by introducing transfer function application to the microphone input path. This parameter change enables the filter to adaptively cancel audio feedback using the same processing mechanisms already in place for noise cancellation, thereby improving feedback suppression without increasing overall processing volume.
3Object-affected harmful factors
If active noise control and echo cancellation are performed, then noise and echo are reduced, but audio feedback occurs due to speaker-microphone proximity
Solution Approach 1:
The patent applies preliminary anti-action by processing the first area microphone input signal through the transfer function of the second area speaker before it enters the noise canceling adaptive filter. This pre-processing step anticipates and counteracts the audio feedback path, allowing the filter to cancel both noise and feedback simultaneously without the feedback interference that would otherwise occur due to speaker-microphone proximity.
Solution Approach 2:
The transfer function of the second area speaker acts as an intermediary element that models the audio feedback path. By introducing this transfer function as an intermediate processing step, the system can predict and cancel the feedback signal before it creates harmful interference, enabling simultaneous noise control, echo cancellation, and feedback suppression.
Data Source
AI summary
A noise canceling adaptive filter outputs, from a front seat speaker, a noise canceling sound generated by applying a transfer function X(z) adapted by an adaptive operation using an output of a front seat microphone as an error to an output sound of a sound source apparatus. An output of the front seat microphone is added to an output of an audio feedback canceling filter by a second adder, added to an output sound of the sound source apparatus by a third adder, and output from a rear seat speaker. The audio feedback canceling filter applies a transfer function X′(z) and a transfer function C{circumflex over ( )}(z) on an output of the second adder and outputs a resultant. The transfer function C{circumflex over ( )}(z) corresponds to a transfer function C(z) from the front seat speaker to the front seat microphone. In synchronization control, the transfer function X(z) is set as the transfer function X′(z).