Multi-Band Audio Compression for Clear Calls in Noisy Environments
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Solution Overview
Problem
Handheld wireless communications devices face challenges in enhancing audio signal quality during voice conversations, particularly in noisy environments, due to limitations in dynamic range compression and noise suppression techniques.
Innovation Solution
The implementation of a multi-band compressor with programmable thresholds in both uplink and downlink audio processors, which splits the audio signal into multiple bands and applies distinct compression and expansion strategies to each band, ensuring improved sound quality and reduced acoustic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a compressor reduces the dynamic range of an audio signal to improve audibility in noisy environments, then quiet sounds become more audible, but loud sounds lose their dynamic variation and perceived quality
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a band splitter, with each band processed independently by separate compressor blocks. This allows different compression ratios and thresholds to be applied to different frequency ranges, preserving dynamic variation in critical bands while compressing bands that benefit from reduced dynamic range for noise masking.
Solution Approach 2:
Different compression characteristics are applied to different frequency bands based on their specific requirements. Each compressor block has programmable thresholds and ratios tailored to its frequency band, enabling localized optimization where quiet bands receive stronger compression for noise suppression while loud bands maintain higher dynamic range for quality preservation.
2Object-affected harmful factors
If a hard limiter is used to limit loud sounds with a high ratio and short attack phase, then loud sounds are effectively limited, but the abrupt manner of limiting causes distortion and degrades sound quality
Solution Approach 1:
The system uses dynamically adjustable compression ratios and attack phases for each frequency band rather than a fixed hard limiter. The compressor blocks can adapt their characteristics in real-time, providing smooth gain reduction with configurable attack and release times that prevent abrupt transitions and distortion while still effectively limiting loud sounds.
3Device complexity
If a single compressor block processes the entire audio signal, then the device complexity is low, but the ability to apply different compression strategies to different frequency bands is limited
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a band splitter, with each band processed independently by separate compressor blocks. This allows different compression ratios and thresholds to be applied to different frequency ranges, preserving dynamic variation in critical bands while compressing bands that benefit from reduced dynamic range for noise masking.
Solution Approach 2:
Multiple compressor blocks are used, each capable of performing the same compression function but with independently programmable parameters. This universal architecture allows the system to adapt to different audio scenarios by configuring each block's thresholds and ratios according to the specific requirements of its frequency band.
4Object-affected harmful factors
If compression is applied to reduce the dynamic range, then the perceived loudness of quiet sounds increases, but the overall dynamic range reduction may cause loss of auditory detail
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a band splitter, with each band processed independently by separate compressor blocks. This allows different compression ratios and thresholds to be applied to different frequency ranges, preserving dynamic variation in critical bands while compressing bands that benefit from reduced dynamic range for noise masking.
Solution Approach 2:
Different compression characteristics are applied to different frequency bands based on their specific requirements. Each compressor block has programmable thresholds and ratios tailored to its frequency band, enabling localized optimization where quiet bands receive stronger compression for noise suppression while loud bands maintain higher dynamic range for quality preservation.
Data Source
AI summary
An uplink or downlink audio processor contains a multi band compressor that receives an input, uplink or downlink, audio signal. The multi-band compressor has a band splitter that splits the input audio signal into a number of different band signals. Each band signal is input to a respective compressor block, which is independently programmable so that its audio frequency response (a) differs from a linear response in at least two non-overlapping windows of its input signal, and (b) differs from the frequency response of another one of the compressor blocks. Other embodiments are also described and claimed.