Acoustic Sensor Placement for Feedback Suppression
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Solution Overview
Problem
Acoustic-electric instruments face challenges with audio feedback due to interactions between the sound board, sensors, and amplifiers, leading to unwanted muddy and booming tones on the low-end of the acoustic frequency spectrum, which affects the quality and clarity of sound.
Innovation Solution
A feedback suppression acoustic sensor system that includes a main acoustic sensor and a feedback suppression sensor, where the feedback suppression sensor is positioned outside an ellipse centered around the sound board string coupling point to detect attenuated string vibrations, and a mixing circuit cancels out sound board vibration signatures from both sensors, producing a mixed output signal that rejects audio feedback while retaining the unique characteristic sound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sound board sensor is used to detect string vibrations, then the characteristic sound of the instrument is retained, but audio feedback occurs causing muddy and booming tones
Solution Approach 1:
The sound board is divided into multiple sensing zones with sensors positioned at specific locations (e.g., near bridge, near sound hole, at bracing points) to capture different vibration modes. This segmentation allows selective cancellation of feedback frequencies while preserving desired tonal characteristics from different regions of the sound board.
Solution Approach 2:
The system uses feedback suppression sensors positioned to detect feedback vibrations, and a signal processing circuit that actively cancels feedback frequencies by generating anti-phase signals. This creates a negative feedback loop that reduces or eliminates the harmful feedback tones while preserving the natural instrument sound.
2Reliability
If multiple sensors are added to improve sound quality and reduce feedback, then audio performance is enhanced, but device complexity increases
Solution Approach 1:
Multiple sensor signals are combined in a summing circuit that processes all sensor outputs simultaneously. The system merges the signals from various sensor locations and uses a single feedback suppression algorithm to handle all feedback frequencies, reducing the need for separate processing circuits for each sensor and simplifying the overall system architecture.
Solution Approach 2:
The feedback suppression circuit is designed to handle multiple sensor inputs and multiple feedback frequencies simultaneously through a universal signal processing approach. The same circuitry and algorithm used for single-sensor feedback suppression are extended to handle multiple sensors, making the system multi-functional without proportionally increasing complexity.
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
The system effectively reduces or eliminates feedback, providing a clear and crisp sound with enhanced string-to-string balance, suitable for professional performances, and offers a passive, battery-free, and minimally intrusive solution for various acoustic instruments.
Implementation Method 1
Some embodiments may include an acoustic guitar pickup that offers the richness of a soundboard sensor (SBT) with the feedback immunity of a undersaddle sensor (UST)
Implementation Method 2
a mixing circuit may at least partially cancel out sound board vibration signatures output by the main and feedback suppression acoustic sensors with one another to produce a mixed output signal
Data Source
AI summary
Apparatus and associated methods relate to acoustic-electric sensor system including a main acoustic sensor operably coupled to detect string vibrations of an acoustic-electric instrument and a feedback suppression acoustic sensor configured to primarily detect sound board vibrations of the acoustic-electric stringed instrument at a location with a substantially attenuated string vibration signal relative to its sound board vibration signal. In an illustrative example, a mixing circuit may at least partially cancel out sound board vibration signatures output by the main and feedback suppression acoustic sensors with one another to produce a mixed output signal. The feedback suppression acoustic sensor may be spaced outside of an ellipse substantially centered around a sound board string coupling point. The main acoustic sensor may be arranged in close proximity to receive the string vibration signal. The mixed output signal may substantially reject audio feedback disturbances while retaining the unique characteristic sound of the instrument.