Pitch Detection Using Multi-Rate Envelope Generators
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Solution Overview
Problem
Existing techniques for detecting sound pitch information from sound signals, such as autocorrelation and envelope-based methods, face challenges in accurately identifying pitches across a wide frequency range due to issues like overtone interference and high computational complexity, leading to inaccurate detection and limited frequency range accuracy.
Innovation Solution
A pitch information generation device comprising multiple envelope generators with different rate of change settings for distinct sound ranges, along with a frequency characteristics adjuster, to generate and identify pitch information with enhanced accuracy across a broader frequency spectrum using a smartphone or tablet device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single envelope generator uses a small time constant for fast response, then the envelope sharply attenuates and follows the waveform quickly, but the envelope is held at small amplitude causing erroneous detection of overtone peaks instead of fundamental tone peaks
Solution Approach 1:
The patent divides the pitch detection process into multiple parallel envelope generators, each with different time constants optimized for specific frequency ranges. This segmentation allows each generator to operate with appropriate response characteristics for its target range, resolving the contradiction between fast response and accurate detection.
Solution Approach 2:
Different envelope generators are assigned different time constants based on their target frequency ranges. Low-frequency generators use larger time constants for stable fundamental tone detection, while high-frequency generators use smaller time constants for faster response to erratic peaks. This local optimization resolves the universal contradiction in the patent.
2Measurement precision
If a single envelope generator uses a large time constant for stable amplitude, then the envelope attenuates slowly and maintains large amplitude, but the fundamental tone peaks may fall below the hold level in erratic waveform ranges, preventing accurate pitch detection
Solution Approach 1:
The patent segments the frequency range into multiple bands, each handled by a dedicated envelope generator with time constants optimized for that range. This allows stable amplitude tracking in low frequencies and fast response in high frequencies, resolving the contradiction between stability and responsiveness.
Solution Approach 2:
The patent changes the time constant parameter based on the target frequency range. By adjusting this critical parameter across different envelope generators, the system achieves both stable amplitude maintenance and fast response characteristics where needed, resolving the contradiction.
3Measurement precision
If autocorrelation is used for pitch detection, then pitch information can be detected from waveforms, but a larger amount of calculation is involved compared to envelope-based methods
Solution Approach 1:
The patent replaces the computationally intensive autocorrelation method with an envelope-based detection system. This substitution reduces calculation complexity while maintaining pitch detection capability, resolving the contradiction between detection capability and computational burden.
Solution Approach 2:
The patent changes the fundamental detection parameter from waveform correlation to envelope amplitude tracking. This parameter change simplifies the calculation process while preserving the ability to detect pitch information, resolving the contradiction between accuracy and complexity.
4Measurement precision
If multiple pitch detectors are used to detect multiple pieces of pitch information, then the optimum piece can be selected, but the device complexity and calculation amount increase
Solution Approach 1:
The patent segments the frequency range into multiple bands with dedicated envelope generators, replacing multiple general-purpose pitch detectors. This segmentation reduces device complexity by using simpler, specialized components instead of multiple complex detectors, while maintaining the ability to handle different frequency characteristics.
Solution Approach 2:
Each envelope generator is optimized for a specific frequency range with appropriate time constants, providing local optimization without requiring multiple full-featured pitch detectors. This reduces overall system complexity while maintaining detection accuracy across the full frequency range.
Data Source
AI summary
A pitch information generation device includes a first envelope generator configured to generate, with regard to a first sound range, a first envelope that attenuates at a first rate of change from a detected value corresponding to a peak in the sound signal, a second envelope generator configured to generate, with regard to a second sound range, which includes a sound range of higher frequency than the first sound range, a second envelope that attenuates from a detected value corresponding to a peak in the sound signal at a second rate of change. The second rate of change is greater than the first rate of change. A pitch information identifier is configured to identify the pitch information based on the first envelope and the second envelope.