AES E-Library

E. Thuillier, O. Lähdeoja, and V. Välimäki, "Feedback Control in an Actuated Acoustic Guitar using Frequency Shifting," J. Audio Eng. Soc., vol. 67, no. 6, pp. 373-381, (2019 June.). doi: https://doi.org/10.17743/jaes.2019.0013 E. Thuillier, O. Lähdeoja, and V. Välimäki, "Feedback Control in an Actuated Acoustic Guitar using Frequency Shifting," J. Audio Eng. Soc., vol. 67 Issue 6 pp. 373-381, (2019 June.). doi: https://doi.org/10.17743/jaes.2019.0013
Abstract: Recent research demonstrated that the classical guitar can be advantageously augmented using a pickup to drive an actuator mounted on the guitar’s back plate. This allows enrichment of the instrument’s timbral palette with audio effect processors in the loop. The feedback problem that results from such a setup is similar to what occurs in live music performance setups where the sound of a guitar is amplified using a loudspeaker. In the present case, measurements of the augmented guitar’s open-loop response demonstrate that instabilities are susceptible to occurring from the string’s modes and not from the guitar’s sound-box. In particular, the shape of the magnitude response suggests frequency shifting as a viable solution to string instability. Introduction of an upward frequency shift in the forward path is proposed as a means for stabilizing the closed-loop system. Experimental results demonstrate that the proposed solution leads to improved stability even for a modest frequency shift of 3 Hz. The achieved gain margin improvement, which is shown to be of at least 3 dB, then comes at the cost of a clearly perceptible amplitude modulation, which may be acceptable in conjunction with other audio effects chosen by the performer.

@article{thuillier2019feedback,
author={thuillier, etienne and lähdeoja, otso and välimäki, vesa},
journal={journal of the audio engineering society},
title={feedback control in an actuated acoustic guitar using frequency shifting},
year={2019},
volume={67},
number={6},
pages={373-381},
doi={https://doi.org/10.17743/jaes.2019.0013},
month={june},} @article{thuillier2019feedback,
author={thuillier, etienne and lähdeoja, otso and välimäki, vesa},
journal={journal of the audio engineering society},
title={feedback control in an actuated acoustic guitar using frequency shifting},
year={2019},
volume={67},
number={6},
pages={373-381},
doi={https://doi.org/10.17743/jaes.2019.0013},
month={june},
abstract={recent research demonstrated that the classical guitar can be advantageously augmented using a pickup to drive an actuator mounted on the guitar’s back plate. this allows enrichment of the instrument’s timbral palette with audio effect processors in the loop. the feedback problem that results from such a setup is similar to what occurs in live music performance setups where the sound of a guitar is amplified using a loudspeaker. in the present case, measurements of the augmented guitar’s open-loop response demonstrate that instabilities are susceptible to occurring from the string’s modes and not from the guitar’s sound-box. in particular, the shape of the magnitude response suggests frequency shifting as a viable solution to string instability. introduction of an upward frequency shift in the forward path is proposed as a means for stabilizing the closed-loop system. experimental results demonstrate that the proposed solution leads to improved stability even for a modest frequency shift of 3 hz. the achieved gain margin improvement, which is shown to be of at least 3 db, then comes at the cost of a clearly perceptible amplitude modulation, which may be acceptable in conjunction with other audio effects chosen by the performer.},}

TY - paper
TI - Feedback Control in an Actuated Acoustic Guitar using Frequency Shifting
SP - 373 EP - 381
AU - Thuillier, Etienne
AU - Lähdeoja, Otso
AU - Välimäki, Vesa
PY - 2019
JO - Journal of the Audio Engineering Society
IS - 6
VO - 67
VL - 67
Y1 - June 2019 TY - paper
TI - Feedback Control in an Actuated Acoustic Guitar using Frequency Shifting
SP - 373 EP - 381
AU - Thuillier, Etienne
AU - Lähdeoja, Otso
AU - Välimäki, Vesa
PY - 2019
JO - Journal of the Audio Engineering Society
IS - 6
VO - 67
VL - 67
Y1 - June 2019
AB - Recent research demonstrated that the classical guitar can be advantageously augmented using a pickup to drive an actuator mounted on the guitar’s back plate. This allows enrichment of the instrument’s timbral palette with audio effect processors in the loop. The feedback problem that results from such a setup is similar to what occurs in live music performance setups where the sound of a guitar is amplified using a loudspeaker. In the present case, measurements of the augmented guitar’s open-loop response demonstrate that instabilities are susceptible to occurring from the string’s modes and not from the guitar’s sound-box. In particular, the shape of the magnitude response suggests frequency shifting as a viable solution to string instability. Introduction of an upward frequency shift in the forward path is proposed as a means for stabilizing the closed-loop system. Experimental results demonstrate that the proposed solution leads to improved stability even for a modest frequency shift of 3 Hz. The achieved gain margin improvement, which is shown to be of at least 3 dB, then comes at the cost of a clearly perceptible amplitude modulation, which may be acceptable in conjunction with other audio effects chosen by the performer.