Strain-Gauge Sensors Eliminate Acoustic Feedback in Amplified Acoustic Stringed Instruments
A new concept in the sound reinforcement of acoustic stringed instruments retains the instrument's acoustic properties and overcomes the limitations of current techniques by solving the problem in two steps. Step 1 uses strain gauges as sensing elements arranged to be insensitive to direct excitation of the instrument's body by airborne sound. Measurements made on a class guitar are given. In this application an instrument gain figure of merit is defined, with strings damped or undamped, which may be useful for judging the maximum sound reinforcement available. Step 2, using a special sound processor as an analog simulator of the instrument's body (or of a piano's soundboard), reintroduces the body characteristics into the picked-up signal. This step 2 can be applied even where no acoustic body exists, and leads to new applications. Strain gauges can also be used as pickup elements for the times of electric pianos.
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