Audio Intelligibility Enhancement via Formant Slope Processing
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Solution Overview
Problem
Ambient noise interferes with audio playback in communication and entertainment systems, causing masking phenomena that prevent clear reception of audio signals, especially in two-way communication systems where the far-end talker is unaware of the listener's noise conditions.
Innovation Solution
A method and circuit for processing audio signals to enhance intelligibility by obtaining an envelope, determining its logarithm and slope, and applying a scaled slope value to the signal to generate an enhanced output, which can also account for noise power estimates to dynamically adjust the enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If ambient noise is present in the listening environment, then the audio signal becomes masked and intelligibility decreases, but increasing the audio signal amplitude may cause distortion or exceed system capabilities
Solution Approach 1:
The patent applies parameter changes by modifying the spectral characteristics of the audio signal through selective amplification of specific frequency bands. The system identifies formant frequencies (resonant frequencies important for speech intelligibility) and applies targeted gain enhancement to these bands, thereby improving speech intelligibility without uniformly increasing overall signal amplitude that could cause distortion.
Solution Approach 2:
The patent implements local quality by applying different enhancement gains to different frequency bands rather than uniform processing. The system analyzes the spectral content and applies selective amplification to specific frequency regions where speech formants occur, leaving other frequency regions unchanged. This localized approach improves intelligibility while maintaining natural sound quality and avoiding overall signal distortion.
2Loss of information
If the far-end talker increases voice amplitude to compensate for noise, then audibility improves, but the system becomes less adaptable to varying noise conditions at the listener's location
Solution Approach 1:
The patent implements feedback by using the near-end microphone to capture ambient noise at the listener's location and feeding this information back to the far-end transmitter. The system analyzes the noise spectrum and automatically adjusts the audio signal enhancement parameters accordingly, creating a closed-loop adaptive system that responds to real-time noise conditions without requiring manual intervention.
Solution Approach 2:
The patent applies dynamics by making the signal enhancement parameters variable and adaptive rather than fixed. The system continuously monitors noise conditions and dynamically adjusts the formant enhancement gains based on the measured ambient noise spectrum, allowing the system to adapt to varying noise conditions such as passing vehicles or changing environmental acoustics.
3Loss of information
If selective formant enhancement is applied to improve speech intelligibility, then consonant sounds become sharper and more understandable, but the processing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the audio signal into multiple frequency bands and processing each band separately. The system identifies specific formant frequency regions and applies enhancement only to these segmented frequency portions, rather than processing the entire spectrum uniformly. This segmented approach improves consonant intelligibility while keeping processing complexity manageable by focusing computational resources on critical frequency regions.
Data Source
AI summary
A method for processing an input signal to create an enhanced output signal includes obtaining an envelope of the input signal, determining a logarithm signal of the envelope, determining a rate of change of the logarithm signal to obtain a slope value, and applying a value derived from the slope value to the input signal to thereby generate an enhanced output signal.