# Spatial Information on Voice Generation from a Multi-Channel Electroglottograph
## 1 Introduction  
The study of musical acoustics includes several aspects about the physics of musical instruments, and the main purpose consists of describing their sound [1], including the development of new physical parameters [2]. One of the most important applications of these studies is to emulate their sound by means of the proper description of their behavior, by means of convolution between the music piece played by the musician and impulse responses of the instrument [3]. However, sound production in humans is a complex process depending on different singing styles, which involves several anatomic structures [4]. This process is responsible for the generation of formant frequencies [5]. For these reasons, it is necessary to properly describe their movements, also including nonlinear aspects, in order to emulate nonlinearities using novel approaches [6; 7]. Considering these aspects, it would be feasible to obtain a proper reconstruction of the diffuseness of musical signals for subjective evaluations [8].  
Nevertheless, the interest in the description and modelling of the phonetic act includes researchers working in medicine and singing teaching. This interest has grown in the last few years and is continuing to grow even more.  
Scientific studies of the human voice started with [PERSON], who gave a detailed explanation of this phenomenon in 1863, describing that the voice is produced by a steady flow of air from the lungs, segmented at the laryngeal level into a series of air puffs at a fundamental frequency (f0) that generates higher harmonics in the cavity of the upper airway. The supra-laryngeal cavity plays the role of a resonator, only filtering some frequencies, and finally the mouth and nose cavities modify the air flux, generating sound [9].  
Mechanically, the phenomenon can be compared with the pression provoked by a piston. The air pressure forces the vocal folds to open. As the suction produced by the drop in pressure in the region of the folds plus static tissue forces begins to counterbalance the subglotic pressure in the region of the lungs, the folds begin to move inward, and the narrowing channel causes an increase in suction until the folds snap shut. Once the vocal fold cycle is completed, the folds return to the starting position.  
Complex laryngeal manoeuvres occur during swallowing and singing register changes. These actions require an accurate synchronization of vocal fold addiction or abduction and the change of the larynx position. The simultaneous assessment of glottal dynamics and larynx position could be beneficial for several reasons: it might be an important instrument for the diagnosis of disordered voice or speech production and swallowing, it might be useful in the research of effective correlations between the control of the speech frequency f0 and the position of the larynx, and it can also be an instrument for the mechanic evaluation of singing techniques. Currently, the existing tools normally available do not allow this simultaneous assessment because of their features (e.g., the incompatibility between MRI and other electric devices) or low resolution (e.g., CT).  
For the aforementioned reasons, there is interest in a device which might be capable of making both the measurements at the same time. This is the reason why a prototype of MC-EGG (Multi-Channel Electroglottopgraph) was realized. This new device differs from a standard EGG in that more electrodes are rapidly switched to give information about the larynx position inside the neck [10].