Here 3D larynx models whose viscoelastic properties of the superficial tissues of the true vocal folds were altered in specific regions at the glottis — producing different left-right fold asymmetries — are analyzed. The idea is to initiate studies about the dynamic of larynges under possible pathological conditions. All simulations used a strategy based on the finite element method to solve a fluid-structure interaction (airflow in the larynx) with a contact-impact problem (glottal closure). The results show that glottal closure is directly influenced by the presence and location of a stiffer mass in the surface of one of the vocal folds. Changes in glottal signal F0 (up to +13.7Hz), open quotient (up to 0.5812), and relative jitter (up to 15.2381%) were observed and are discussed here.