Quantifying the Vibrational Response of Acoustic Guitars
Level of Education of Students Involved
Mechanical Engineering, Physics
It is commonly accepted that the sound produced by acoustic guitars is largely dependent upon the size, shape, and orientation of the braces on the underside of the guitar’s front panel, which is the sound board. In general, luthiers have approached the construction of guitars from an artistic, qualitative standpoint, resulting in there being little quantitative data available. To quantify what makes an acoustic guitar sound the way that it does, we developed an apparatus that measures the soundboard’s vibrational response by placing an accelerometer on the soundboard while striking the guitar’s bridge with an impact hammer. Since the bridge is the location where the strings attach to the body, the impact hammer stimulates the excitation of the strings. The guitar was divided into a grid, and trials were conducted by moving the accelerometer to different points on the grid until a full map of the guitar soundboard’s response was recorded. Three guitars were tested at the same points with the apparatus: two of the same make and model and one from a different manufacturer. A Frequency Response Function (FRF) was found based on the data measured by the accelerometer. The two similar guitars showed nearly identical responses at the test points, while the guitar from the different manufacturer showed a noticeably different response. These results show that the natural frequency of a guitar's response to external excitation is a key factor in quantifying the qualitative aspects of a guitar’s sound.
Joffe, Nathan and Anderson, Elias, "Quantifying the Vibrational Response of Acoustic Guitars" (2023). Symposium on Undergraduate Research and Creative Expression (SOURCE). 1209.