Pitch Emphasis Apparatus for Natural Audio Signal Processing
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Solution Overview
Problem
Existing audio signal processing techniques fail to naturally enhance pitch components in consonant parts, leading to unnatural sound and discontinuities when switching between vowel and consonant segments.
Innovation Solution
A pitch emphasis apparatus that adjusts the pitch enhancement processing based on the spectral envelope of audio signals, applying a lower pitch gain for consonant segments with flat spectral envelopes and a higher gain for segments with non-flat envelopes, using a damping coefficient that decreases with increasing consonant-likeness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pitch enhancement processing is carried out on all time segments including consonant parts, then pitch components are enhanced throughout the audio signal, but consonant parts sound unnatural to listeners
Solution Approach 1:
The patent applies different pitch enhancement processing to different time segments based on their characteristics. Vowel segments with clear pitch structures receive full pitch enhancement, while consonant segments with flat spectral envelopes receive suppressed or no enhancement. This local differentiation resolves the contradiction by tailoring processing intensity to local signal properties, preventing unnatural sound in consonants while maintaining pitch enhancement in vowels.
Solution Approach 2:
The patent dynamically adjusts the pitch enhancement parameter (pitch gain σ0) based on the spectral envelope characteristics of each time segment. When the spectral envelope is flat (indicating consonant), the pitch gain is suppressed to a lower value. When the spectral envelope is not flat (indicating vowel), the pitch gain is maintained at a higher value. This parameter adaptation resolves the contradiction by matching enhancement intensity to segment type.
2Object-affected harmful factors
If pitch enhancement processing is not carried out on consonant parts, then natural sound is preserved in consonant segments, but pitch components are lost when switching between vowel and consonant segments
Solution Approach 1:
The patent introduces dynamic switching between two processing modes: full pitch enhancement mode for vowel segments and suppressed pitch enhancement mode for consonant segments. The system transitions smoothly between these modes based on real-time spectral envelope analysis, maintaining pitch continuity where needed while preserving natural sound where appropriate. This dynamic adaptation resolves the contradiction between naturalness and continuity.
Solution Approach 2:
The patent applies periodic pitch enhancement processing synchronized with the pitch period T0 of the audio signal. By aligning enhancement operations with the natural periodicity of voiced sounds, the system maintains pitch continuity during vowels while allowing natural consonant characteristics to pass through unchanged. This periodic synchronization resolves the contradiction by rhythmically applying enhancement only when acoustically appropriate.
3Reliability
If pitch enhancement processing switches between time segments for vowels and time segments for consonants, then appropriate processing is applied to each segment type, but frequent discontinuities occur in the audio signal
Solution Approach 1:
The patent applies beforehand cushioning by using a damping coefficient β0 (where 0 < β0 < 1) to smoothly transition between different pitch enhancement modes. When switching from vowel to consonant segments or vice versa, the damping coefficient attenuates abrupt changes in the pitch-enhanced signal, cushioning against discontinuities. This pre-prepared attenuation mechanism resolves the contradiction by preparing for and mitigating transitions before they cause audible artifacts.
Solution Approach 2:
The patent introduces a damping coefficient β0 as an intermediary element that mediates between the full pitch enhancement mode and the suppressed pitch enhancement mode. This damping coefficient acts as a buffer during mode transitions, smoothing the switching between vowel and consonant processing regions. The intermediary damping mechanism resolves the contradiction by providing a smooth transition path that maintains both segment-specific processing accuracy and audio signal continuity.
Data Source
AI summary
Provided is pitch enhancement processing having little unnaturalness even in time segments for consonants, and having little unnaturalness to listeners caused by discontinuities even when time segments for consonants and other time segments switch frequently. A pitch emphasis apparatus carries out the following as the pitch enhancement processing: for a time segment in which a spectral envelope of a signal has been determined to be flat, obtaining an output signal for each of times in the time segment, the output signal being a signal including a signal obtained by adding (1) a signal obtained by multiplying the signal of a time, further in the past than the time by a number of samples T0 corresponding to a pitch period of the time segment, a pitch gain σ0 of the time segment, a predetermined constant B0, and a value greater than 0 and less than 1, to (2) the signal of the time.