Acoustic properties of symmetric and asymmetric vocal fold vibration

To investigate the acoustic properties of signals generated by symmetric and asymmetric vocal fold vibrations, a flow-acoustic splitting method is employed to model the glottal airflow associated with voice production. The perturbed compressible pressure, p′, is calculated by the linearized perturbed compressible equations (LPCE). Based on p′ and the source term of the LPCE, acoustic behavior related to the medial thickness of the vocal fold and the frequency difference between the two sides of the vocal fold are analyzed. The results show that the opposite-polarity source pair is responsible for the production of p′ and the opposite-polarity source pair is located right at the entrance of the glottal gap. The frequency difference of the two sides diminishes the opposite-polarity source pair and causes amplitude modulation of p′. Consequently, asymmetric vibration can lead to voice problems. The increase in the medial thickness makes the distribution of the paired sources more compact and stronger, and it enhances the intensity ratio between the p′ and the hydrodynamic pressure variation, thereby positively contributing to voice production.