Multi-Band Audio Signal Processing With Band-Specific Update Rates
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Solution Overview
Problem
Existing multi-band dynamic range compressors for hearing instruments suffer from undersampling and oversampling issues in different frequency bands, leading to aliasing distortion and inefficient use of computational resources, which affects the perceptual performance and battery life.
Innovation Solution
A multi-band signal processor that allows separate and flexible update rates for different frequency bands, enabling optimal sampling rates based on perceptual performance criteria, thereby avoiding aliasing and reducing computational waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform block rate is used for all frequency bands in FFT-based analysis, then the system is simple to implement, but high frequency components are undersampled causing aliasing distortion
Solution Approach 1:
The patent divides the frequency spectrum into multiple bands and applies different update rates to each band. High frequency bands are updated more frequently than low frequency bands, preventing aliasing distortion while maintaining system manageability through structured segmentation of the frequency domain.
Solution Approach 2:
The system dynamically adjusts the update rate for each frequency band based on its specific requirements. Instead of a static uniform block rate, the update frequency is made adaptive to the characteristics of each band, allowing optimal sampling without requiring complete redesign of the entire processing system.
2Reliability
If a high block rate is used to accommodate high frequency components, then aliasing is avoided, but low frequency bands are oversampled wasting computational resources
Solution Approach 1:
Each frequency band is assigned a locally optimized update rate according to its specific sampling requirements. Low frequency bands use lower update rates while high frequency bands use higher update rates, ensuring that computational resources are allocated efficiently to match the actual needs of each band rather than applying a uniform standard throughout.
Solution Approach 2:
The system changes the block rate parameter differently for different frequency bands. By allowing the update rate parameter to vary across frequency bands rather than remaining constant, the system achieves optimal sampling for each band while reducing overall computational burden compared to using the highest required rate for all bands.
3Productivity
If separate update rates are implemented for different frequency bands, then computational efficiency is optimized and aliasing is prevented, but the system complexity increases
Solution Approach 1:
The patent implements a multi-functional frequency domain transform processor that can operate at different update rates for different frequency bands using a single integrated architecture. This universal processor handles both low and high frequency bands with appropriate rate adjustments, avoiding the need for separate processing systems for each band and thereby limiting the increase in overall system complexity.
Data Source
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AI summary
The present invention relates to a multi-band signal processor comprising a signal input for receipt of a digital audio input signal and a cascade of digital all-pass filters configured for receipt of the digital audio input signal and generation of M delayed digital audio signal samples at respective tapping nodes interposed between the digital all-pass filters. The multi-band signal processor comprises a signal convolution processor configured for convolving the M delayed digital audio signal samples with M time-varying filter coefficients of a processing filter to produce a processed digital output signal. A frequency domain transform processor is configured for converting the M delayed digital audio signal samples to frequency domain representation to produce respective signal spectrum values in a predetermined number of frequency bands, N. A level estimator is configured to compute respective signal level estimates in the predetermined number of frequency bands based on the respective signal spectrum values. A processing gain calculator of the multi-band signal processor is configured for computation of a frequency domain gain coefficient for each of the predetermined number of frequency bands based on the respective signal level estimates and band gain laws. An inverse frequency domain transform processor is configured for conversion of the N frequency domain gain coefficients into the M time-varying filter coefficients of the processing filter. The frequency domain transform processor is configured to compute signal spectrum values of at least two different frequency bands at different band update rates. Each of M and N is a positive integer number.