Root Cause Analysis of Rocking Modes

Cardenas W, Klippel W. Root Cause Analysis of Rocking Modes. J Audio Eng Soc. 2016;64(12):969-977. doi:10.17743/jaes.2016.0046

@article{Cardenas2016_18531,
  author = {Cardenas, William and Klippel, Wolfgang},
  title = {{Root Cause Analysis of Rocking Modes}},
  journal = {Journal of the Audio Engineering Society},
  volume = {64},
  number = {12},
  pages = {969--977},
  year = {2016},
  month = dec,
  publisher = {Audio Engineering Society},
  doi = {10.17743/jaes.2016.0046},
  url = {https://doi.org/10.17743/jaes.2016.0046}
}

TY  - JOUR
TI  - Root Cause Analysis of Rocking Modes
AU  - Cardenas, William
AU  - Klippel, Wolfgang
T2  - Journal of the Audio Engineering Society
J2  - J. Audio Eng. Soc.
VL  - 64
IS  - 12
SP  - 969
EP  - 977
PY  - 2016
DA  - 2016/12/06
DO  - 10.17743/jaes.2016.0046
UR  - https://doi.org/10.17743/jaes.2016.0046
PB  - Audio Engineering Society
LA  - en
AB  - Most micro-speakers, headphones, and some cone loudspeakers exhibit undesired rotational vibration patterns called rocking modes. These are caused by inhomogeneous distribution of mass, stiffness, and force factor shifting the center of gravity, stiffness, and electrodynamic excitation away from the pivot point, which is the cross point of the nodal lines of the two rocking modes. This paper focuses on practical measurements of rocking modes using laser vibrometry, parameter identification, and root cause analysis. New characteristics are presented that simplify the interpretation of the identified parameters. Due to the high quality factor of the rocking resonators, only a very small asymmetrical force is required (which is usually a few percent of the transversal force) to generate a critical rocking behavior having more energy than the desired piston mode. Assessing the relative rocking level and identifying the imbalances is a convenient way to keep voice coil rubbing under control and to avoid impulsive distortion impairing the quality of the reproduced sound. A new technique was validated by numerical simulations and systematic modifications of a real transducer. The diagnostic value of the new measurement technique is illustrated on a transducer used in headphones.
ER  -