Instrumental Analysis of Voice Function

Instrumental voice analysis techniques aim to objectively describe characteristics of vocal production and output. For both clinical and research questions, a variety of instrumental methods to describe features of the three main subsystems of voice production, phonation, respiration, and resonance, are available. Assessment techniques are mainly classified as direct methods to visualize the physiology and activity of laryngeal structures such as by laryngostroboscopy or videokymography (VKG), and indirect methods to objectively assess acoustic properties of the human voice sound (i.e. vocal output). Moreover, semi‐direct methods provide information regarding vocal fold and respiration physiology without visualizing, and include electromyography, subglottal pressure estimates, and electroglottography (Awan, 2008). In a diagnostic setting, clinicians aim to determine the cause and consequences of disordered voice production to tailor a specific treatment for the individual patient. A disordered voice production may result from changes in the structure (such as vocal fold nodules or edema), innervation (such as in vocal fold paralysis), or muscular function of the phonatory system. Therefore, as recommended by European and American clinician associations, a comprehensive voice examination usually includes subjective, visual, perceptual, aerodynamic, and instrumental acoustic assessment techniques (Dejonckere et al., 2001; Patel et al., 2018). Scope of the present chapter is to review advantages, disadvantages and applications of the most widely used indirect instrumental acoustic and direct visual assessment techniques applied in voice diagnostics and research.