Signal Processing Device for Stringed Instrument Resonance Control
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Solution Overview
Problem
Existing technologies for amplifying stringed instruments, such as acoustic guitars, fail to allow users to intentionally emphasize or suppress the resonant sound of the instrument's body, leading to complex frequency adjustments and potential howling issues when using piezoelectric pickups and microphones.
Innovation Solution
A signal processing device with a filter unit comprising FIR, IIR filters, and a manipulation unit that allows users to adjust filter coefficients to control the resonant sound's frequency response, preventing howling by selectively changing peak values in specific frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an equalizer is used to adjust the level of each frequency to emphasize or suppress resonant sound components, then the user can control the resonant sound characteristics, but the manipulation becomes complex since the user needs to search for specific frequencies and adjust multiple frequency levels
Solution Approach 1:
The frequency spectrum is segmented into multiple predetermined frequency bands, with each band corresponding to a specific resonant frequency of the stringed instrument body. This segmentation allows the user to control each resonant frequency independently through simple volume adjustments rather than searching through the entire frequency spectrum, thereby maintaining adaptability while significantly improving ease of operation.
Solution Approach 2:
The system changes the volume parameter of each frequency band independently through a filter unit. By adjusting the volume of predetermined frequency bands that correspond to resonant frequencies, the system enables users to emphasize or suppress specific resonant sound components with simple operations, avoiding the complexity of traditional equalizer manipulation.
2Power
If the electrical signal representing resonant sound of the body is amplified after convolution operation, then the volume of resonant sound increases, but the body and strings may additionally resonate due to peak components at specific frequencies, thereby causing howling
Solution Approach 1:
The system dynamically adjusts the volume of each frequency band based on the desired output level. By independently controlling the volume of predetermined frequency bands corresponding to resonant frequencies, the system can amplify resonant sound to increase volume while suppressing specific peak components that cause howling, thus achieving dynamic control over both volume and stability.
Solution Approach 2:
The filter unit applies different volume adjustments to different frequency bands locally. Each frequency band corresponding to a resonant frequency can be independently emphasized or suppressed, allowing the system to amplify overall resonant sound volume while selectively reducing problematic peak components that cause howling, thereby resolving the contradiction between volume and stability.
3Power
If a piezoelectric element is used for the pickup to convert string vibration into an electrical signal, then the volume can be increased through amplification, but the influence of resonant sound of the body is reduced
Solution Approach 1:
The filter unit acts as an intermediary between the piezoelectric pickup signal and the final output. It processes the electrical signal by adjusting the volume of predetermined frequency bands corresponding to body resonant frequencies, thereby adding the missing resonant characteristics back into the signal while maintaining the volume benefits of electronic amplification, thus restoring authenticity without sacrificing power.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables users to simply adjust the resonant sound's volume and prevent howling by modifying peak values in the frequency response, maintaining the instrument's sound quality and resonance characteristics.
Implementation Method 1
convolution operation is also performed on the signal using a Finite Impulse Response (FIR) filter to add a resonant sound or the like of the body to the signal
Implementation Method 2
an Infinite Impulse Response (IIR) filter which processes the electrical signal
Implementation Method 3
a piezoelectric element for the pickup to convert string vibration into an electrical signal
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A signal processing device is composed of an acquiring unit, a filter unit and a changing unit. The acquiring unit acquires a signal indicating vibration of a string. The filter unit performs convolution operation on the signal acquired by the acquiring unit according to a filter coefficient and outputs a resulting signal. The filter coefficient is set such that the resulting signal has a frequency response containing a plurality of peak waveforms associated with resonance of a body of a stringed instrument within a specific frequency range. The changing unit changes the filter coefficient so as to change a peak value of each of the peak waveforms while maintaining a width of each of the peak waveforms in the frequency response.