Low-Latency Multi-Driver Adaptive Noise Canceling System
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Solution Overview
Problem
Existing personal audio devices with adaptive noise cancellation (ANC) systems face reduced effectiveness due to latency introduced by crossovers when using multiple transducers for different frequency bands, which impede high-quality audio reproduction.
Innovation Solution
A personal audio system with separate low-frequency and high-frequency transducers, an integrated circuit, and adaptive noise-canceling functionality that uses a reference microphone to generate anti-noise signals directly for each transducer, eliminating the need for crossover filtering and maintaining low-latency ANC operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a crossover module is used to split signals between low-frequency and high-frequency transducers, then high-quality audio reproduction is achieved, but latency is introduced that reduces ANC effectiveness
Solution Approach 1:
The patent divides the ANC signal processing into separate parallel paths for low-frequency and high-frequency transducers. Each path has its own adaptive filter that processes the reference microphone signal independently, eliminating the need for a centralized crossover module and reducing latency in the ANC path.
Solution Approach 2:
The adaptive filters for each transducer path are configured in advance to process only the relevant frequency components. This preliminary filtering approach allows direct processing of reference signals without requiring post-crossover delay compensation, maintaining low latency while achieving frequency-specific noise cancellation.
2Manufacturing precision
If separate transducers are used for high and low frequencies, then audio quality is improved, but device complexity increases
Solution Approach 1:
The reference microphone serves multiple functions: it captures ambient noise for ANC processing and provides the reference signal for all frequency bands simultaneously. This multi-functional approach reduces the need for additional sensors while supporting multiple transducer types.
Solution Approach 2:
The patent changes the frequency response parameters of adaptive filters to match the characteristics of different transducers. By adjusting filter parameters rather than adding complex hardware, the system accommodates multiple transducer types while maintaining manageable complexity.
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 solution effectively cancels ambient noise across different frequency bands, enhancing audio intelligibility and quality by minimizing latency and ensuring that anti-noise signals are generated and applied only where necessary, thereby improving the overall ANC performance.
Implementation Method 1
A reference microphone is mounted on the device housing to provide a reference microphone signal indicative of the ambient audio sounds
Implementation Method 2
Adaptive filters are used to generate the anti-noise signals by filtering the reference microphone signal, such that the anti-noise signals cause substantial cancellation of the ambient audio sounds at their corresponding transducers
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A personal audio device including multiple output transducers for reproducing different frequency bands of a source audio signal, includes an adaptive noise canceling (ANC) circuit that adaptively generates an anti-noise signal for each of the transducers from at least one microphone signal that measures the ambient audio to generate anti-noise signals. The anti-noise signals are generated by separate adaptive filters such that the anti-noise signals cause substantial cancelation of the ambient audio at their corresponding transducers. The use of separate adaptive filters provides low-latency operation, since a crossover is not needed to split the anti-noise into the appropriate frequency bands. The adaptive filters can be implemented or biased to generate anti-noise only in the frequency band corresponding to the particular adaptive filter. The anti-noise signals are combined with source audio of the appropriate frequency band to provide outputs for the corresponding transducers.