## 3 Problem Statement  
Our general motivation to conduct the experiments using various types of recordings is an attempt at reliably assessing all aspects of speech signal generation and changes ongoing within the articulation, phonation, and prosody processes in people with Parkinson's disease. Four systems based on features related to phonation, articulation, prosody, and their fusion are analyzed. Extracting features that characterize phonation, articulation, and prosody is justified by previous studies showing that impairment of speech in PD is reflected by all these features, which helps in the automatic classification of PD [45; 77]. Based on the literature review, disorders associated with PD depend on their stage and can manifest themselves at various levels of speech signal generation. Some patients have weaker muscles of the larynx, which influence phonation. Other ones have a great problem with the pharyngeal cavity, which influences the articulation process. Last but not least, some patients could have a problem with the emotion that influences prosody of speech. It depends on the research group. Consequently, tools based on only one aspect will favor false-negative rates with respect to approaches considering several aspects. Therefore, the complementarity between the articulatory, phonatory, and prosody information should be the basis for the objective detection of PD.  
In the related papers presented above, the authors do not report the level of severity of disease symptoms among PD patients. The real problem of this kind of research is trying to make the correct diagnosis at an early stage of the disease when the severity of classic symptoms is low. The conducted research presents an approach which includes this issue. The group of patients who had PD were in the so-called ON phase. This kind of phase minimizes the level of severity of disease symptoms among PD patients due to drugs taken. According to the searches, when patients are under the influence of levodopa drugs, symptoms and voice disorders disappear or decrease noticeably and reappear after stopping the action of the drug [78]. Levodopa promotes articulation, sound, rhythm, vocal amplitude, and speech intelligibility in patients with PD [67]. During the experiments conducted, a patient taking this medication, in the vast majority of cases, caused the symptoms of the disease to be dormant. At first glance, the patient appeared to be a healthy person. During the tests conducted by the authors in the hospital, such a situation could be observed very often.  
Our suggested approach will allow one to determine the most significant feature subset, taking into account different aspects of speech generation. The use of several types of recordings resulted from our previous experience in the scope of patient recording. It was not directly associated with PD but took into account comorbid conditions. Recordingconditions and a medical examination often induce stress in patients. In the course of the recordings, the patients had a cold, which hindered uttering, e.g., a vowel with prolonged phonation. They were often unable to maintain a stable phonation, precisely due to the ac-companying cold. At the same time, recording other texts was not difficult for them. The use of various recording types within this system may constitute grounds for developing a universal system, independent of available recordings, on the one hand. On the contrary, it will be possible to employ a system that integrates features of different recordings to define a multimodal PD identification system if we have all the recordings.