Speech Signal Frequency Response Adaptation
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Solution Overview
Problem
Speech signals received in varying acoustical or electrical environments often have spectral shapes that are not ideal for specific applications, such as hands-free telephony or speech recognition, leading to suboptimal sound quality and intelligibility.
Innovation Solution
A system and method that adaptively enhances the frequency response of speech signals by calculating an average speech spectral shape estimate using first-order IIR filtering, comparing it to a target spectral shape, and applying a spectral correction factor to normalize the signal, thereby improving the signal's alignment with the desired spectral shape for the intended application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If spectral normalization is performed using fixed reference data, then the system can be simple to implement, but it cannot adapt to slowly varying acoustical or electrical characteristics
Solution Approach 1:
The patent implements dynamic adaptation by continuously updating the spectral normalization parameters based on incoming speech signals. Instead of using fixed reference data, the system employs adaptive algorithms that track changes in acoustical transfer function and electrical characteristics over time, allowing the frequency response to be dynamically adjusted to match ideal spectral shapes for different applications.
Solution Approach 2:
The system performs self-calibration by using the incoming speech signals themselves as reference data. The adaptive normalization process extracts spectral characteristics from the speech signals and automatically adjusts the frequency response without requiring external calibration inputs or manual intervention, enabling the system to self-adapt to changing environmental and electrical conditions.
2Adaptability or versatility
If the system adapts to different applications by changing spectral shapes, then it improves application-specific performance, but it requires multiple spectral shape profiles
Solution Approach 1:
The patent implements application-specific optimization by changing the target spectral shape parameters based on the detected or selected application. Different applications (e.g., hands-free telephony, speech recognition, audio conferencing) have distinct ideal frequency responses, and the system adjusts the normalization target parameters accordingly. This allows a single system to serve multiple applications by dynamically modifying the spectral shaping parameters rather than requiring separate fixed systems for each application.
3Measurement precision
If spectral normalization is applied to improve sound quality, then intelligibility improves, but processing time increases
Solution Approach 1:
The system performs preliminary spectral analysis and adaptation in the background using previously processed speech signals to establish baseline spectral characteristics. This preliminary processing allows the system to pre-compute normalization parameters that can be quickly applied to incoming speech, reducing the real-time processing burden while maintaining high speech intelligibility and quality enhancement.
Data Source
AI summary
A method and system for enhancing the frequency response of speech signals are provided. An average speech spectral shape estimate is calculated over time based on the input speech signal. The average speech spectral shape estimate may be calculated in the frequency domain using a first order IIR filtering or “leaky integrators.” Thus, the average speech spectral shape estimate adapts over time to changes in the acoustic characteristics of the voice path or any changes in the electrical audio path that may affect the frequency response of the system. A spectral correction factor may be determined by comparing the average speech spectral shape estimate to a desired target spectral shape. The spectral correction factor may be added (in units of dB) to the spectrum of the input speech signal in order to enhance or adjust the spectrum of the input speech signal toward the desired spectral shape, and an enhanced speech signal re-synthesized from the corrected spectrum.