## 1 Introduction  
Voice plays an essential role in interpersonal communication. Therefore, healthy voice production is indispensable and pathologies are associated with a significant loss of quality of life. Various professions deal with this subject, including phonitricians and speech language pathologists, whose tasks include the exploration and treatment of voice, speech and language disorders. This area of responsibility also includes gaining a profound understanding of the phonation mechanism that has been researched for many decades [1; 2]. An in-depth understanding of these mechanisms is important to derive new findings about speech system dysfunctions from which new behavioral, medical, and surgical approaches may be developed. The voice originates in the larynx (Figure 1a). Through the core muscles, pressure builds up in the lungs and air is directed through the trachea to the larynx, which causes the vocal folds to oscillate (Figure 1b). By opening and closing of the vocal folds, a fundamental tone is generated (in humans usually between 100-300 Hz for normal phonation [3; 4]), which is modulated in the vocal tract and then emitted through the mouth [5]. Many years of research have made it possible to define certain parameters from which it is feasible to draw conclusions about the histological structures, the voice acoustics and the biomechanical components of the vocal folds. These include a wide variety of aerodynamic and acoustic parameters, as well as parameters computed from high-speed digital imaging (HSI) data [6; 7; 8]. The technical progress and possibility to record high-speed images of the vocal folds during the high frequency phonatory process was a revolution in clinical phoniatric diagnostics. Since the first analog high-speed recording of human vocal folds in 1940 by [PERSON] [9], technology has evolved steadily. In recent years, the cameras have become smaller and faster and the spatial resolution has improved enormously. Particularly when used in the clinical diagnosis of dysphonia, the HSI technique is superior to stroboscopy [10] and it is impossible to imagine phonatory clinical research today without HSI [10; 11; 12; 13; 14; 15; 16]. As long as the frame rate of the camera reaches at least 4000 frames per second, the technique enables one to capture an accurate representation of the vibratory cycle of the vocal folds [17]. From these images and computed parameters, conclusions can be drawn regarding dynamic changes [18] and voice disorders and pathologies [10; 12; 19; 20; 21; 22; 23]. The detected vocal fold vibrations can be subdivided into three classifications [24]. These are type 1 (periodic), type 2 (subharmonic) and type 3 (aperiodic or chaotic) vibrations. Since healthy voice production is assumed to show periodic vibrations [25], the type 1 vibrations in this study are also called normal or non-disordered vibrations. The type 2 and type 3 vibrations are called irregular or disordered vibrations and are often related to voice pathologies [26]. These three types of vibrations have been systematically investigated in various studies over the years [27; 28; 29]. However,  
Figure 1: (**a**) Simplified way of air for voice production in overview; (**b**) Schematic longitudinal section through the larynx with laminar airflow under and turbulent airflow above the vocal folds. not all data can be collected easily in everyday clinical practice from humans. In particular, subglottal measurements cannot (or only under severe conditions) be obtained in vivo; ex vivo experiments on larynxes are necessary [30]. Voice production in humans and mammals is very similar [31]; therefore, animal laryngeal studies have been carried out from which conclusions are drawn regarding human physiology. In the literature, voice production of animals and the comparison with humans has already been examined many times. Sheep, canines [32; 33], porcines [34; 35], and rabbits [36] are particularly suitable for comparison with humans.