This signal is filtered by the vocal tract resonator. Breathing is obviously of relevance to voice production. A desirable voice quality and vocal health are important goals both in singing teachers studios and in voice clinics, and according to experience, breathing strategy is highly relevant to achieve these goals. In particular, many voice disorders, especially in women, are functional, i.e., caused by inappropriate phonatory habits. Voice therapy is often an appropriate treatment where one important component is to give the patient an adequate breathing technique.
Subglottal pressure is regulated by both active and passive forces.
The active forces are supplied by the respiratory muscles. The passive forces are gravity and elasticity. The elasticity forces are strongly dependent on lung volume, high lung volumes producing high positive pressures and low lung volumes producing negative pressures. Therefore, in untrained voices, vocal sounds often tend to be louder when produced at high than at low lung volumes. In trained voices such effects are compensated for by activation of respiratory muscles.