Signal Processing Apparatus for Stringed Instruments
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Solution Overview
Problem
Existing signal processing methods for stringed instruments cause phase interference between string vibration and body resonance signals, leading to reduced low-frequency volume and unnatural instrument sound.
Innovation Solution
A signal processing apparatus that uses a low-pass filter and a high-pass filter with equal cut-off frequencies to mix string vibration and body resonance signals, preventing phase interference and enhancing the naturalness of the instrument sound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pickup signal and an instrument sound signal are mixed to enhance body resonance, then the resonance component is improved, but phase interference occurs causing low-frequency volume reduction
Solution Approach 1:
The signal processing is segmented into three distinct paths: the original pickup signal path, a low-pass filtered path for body resonance enhancement, and a high-pass filtered path for string vibration preservation. This segmentation allows each path to be optimized independently, preventing phase interference while maintaining resonance enhancement benefits
Solution Approach 2:
Frequency-based filtering acts as an intermediary mechanism that separates the pickup signal into low-frequency and high-frequency components. The low-pass filter serves as an intermediary to extract body resonance frequencies, while the high-pass filter serves as an intermediary to preserve string vibration frequencies, thereby avoiding direct phase interference between conflicting signal components
2Reliability
If a FIR filter is used to add body resonance to the pickup signal, then the instrument sound naturalness is improved, but low-frequency volume is reduced due to phase shift
Solution Approach 1:
The signal processing is segmented into three distinct paths: the original pickup signal path, a low-pass filtered path for body resonance enhancement, and a high-pass filtered path for string vibration preservation. This segmentation allows each path to be optimized independently, preventing phase interference while maintaining resonance enhancement benefits
Solution Approach 2:
The cut-off frequency parameter of the low-pass and high-pass filters is optimized to be equal, creating a seamless frequency division. This parameter change ensures that low-frequency components (body resonance) and high-frequency components (string vibration) are separated without overlap or phase interference, maintaining both naturalness and volume
Data Source
AI summary
A signal processing apparatus 30 includes a FIR filter 33 that generates a signal corresponding to an instrument sound including a resonance of a body caused by a vibration of a string, based upon a pickup signal from a pickup sensor 21. The signal processing apparatus 30 guides the pickup signal from the pickup sensor 21 to an adder circuit 35 via a low-pass filter 32, guides the signal generated by the FIR filter 33 to the adder circuit 35 via a high-pass filter, and adds and mixes these signals in the adder circuit 35. The cut-off frequency of the high-pass filter 34 is equal to or higher than the cut-off frequency of the low-pass filter 32.