Multiband Hearing Protection Limiting for Speech Clarity
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Solution Overview
Problem
Hearing protection devices struggle to limit sound pressure levels effectively while maintaining speech intelligibility and avoiding excessive gain reductions, especially in noisy environments where speech and noise occupy different frequency ranges.
Innovation Solution
A hearing protection device with a multiband limiter that divides the microphone input signal into sub-band signals, estimates signal strength parameters, and applies gain reductions only where necessary, using a limiter controller to determine and apply gain reductions based on signal strength parameters to limit broadband output signal strength without affecting speech intelligibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If gain reduction is applied to limit sound pressure levels, then hearing protection is improved, but speech intelligibility deteriorates due to excessive gain reductions
Solution Approach 1:
The patent divides the audio signal into multiple frequency sub-bands using a sub-band splitting module. The multiband limiter then applies gain reduction independently to each sub-band based on its energy level, rather than applying uniform gain reduction across all frequencies. This segmentation allows selective attenuation of noisy frequency ranges while preserving speech frequencies, resolving the contradiction between hearing protection and speech intelligibility.
2Power
If gain reduction is applied in all frequency bands, then broadband power is limited, but speech clarity deteriorates due to unnecessary attenuation in low-energy bands
Solution Approach 1:
The patent applies gain reduction selectively only to sub-bands where it is essential, based on their energy levels. The limiter controller determines which sub-bands require attenuation by comparing their energy against thresholds, and applies gain reduction only to those specific sub-bands rather than uniformly across all frequencies. This local quality approach ensures broadband power is limited while preserving speech clarity in low-energy sub-bands that do not require attenuation.
3Object-affected harmful factors
If noise reduction is applied in noisy environments, then hearing protection is improved, but speech intelligibility may deteriorate if speech and noise frequency ranges overlap
Solution Approach 1:
The patent dynamically adjusts gain reduction for each sub-band based on real-time energy estimation. The estimator module continuously monitors the energy level of each sub-band, and the limiter controller adaptively applies gain reduction only when and where needed. This dynamic approach allows the system to differentiate between speech and noise in different frequency ranges and time moments, reducing noise while preserving speech intelligibility even when frequency ranges overlap.
Data Source
AI summary
A hearing protection device includes: a sub-band splitting module configured to divide a first microphone input signal into sub-band signals having a first sub-band signal and a second sub-band signal; an estimator module configured to estimate signal strength parameters of respective sub-band signals, the signal strength parameters having a first signal strength parameter of the first sub-band signal, and a second signal strength parameter of the second sub-band signal; a multiband limiter; and a limiter controller; wherein the limiter controller is configured to determine gain reductions for the sub-band signals of the first microphone input signal, the gain reductions having a first gain reduction and a second gain reduction, and wherein the limiter controller is configured to control the multiband limiter to apply the second gain reduction to the second sub-band signal, wherein the second gain reduction for the second sub-band signal is based on the first signal strength parameter.