## 1 Introduction  
People widely acknowledge urban parks as places for appreciating tranquility and a restorative soundscape. The term soundscape has previously been defined by different practitioners such as composers, acousticians, architects and psychologists [1; 2; 3]. Within the ISO 12913-1 international standard, the term soundscape is defined as \"the acoustic environment as perceived or experienced and/or understood by a person or people, in context\" [4]. The soundscape is generally considered as not equal to the sound environment, and therefore not measurable using only standard sound measurement equipment. Fundamentally, soundscape is shaped within a context of a person-environment interaction. This context is induced by all sensory stimulations, most importantly by auditory and visual observations. However, other senses, such as smell and touch variably contribute to overall perception. Additionally, context is also shaped by the knowledge that people have accumulated about the space, its use, purpose and cultural meaning, people's motivations and purposes, associated activities and other factors [5]. The soundscape of urban environments has been thoroughly investigated during recent years [6; 7; 8]. Even though the soundscape of urban parks only represents a small subset of all existing soundscape types, its context has been reasonably well described [9; 10; 11]. In this description, urban parks are frequently regarded as calm and tranquil areas within the liveliness of the city. Moreover, the concept of tranquility has been studied in various research areas closely related to soundscape. For instance, a direct brain response with relation to perceived tranquility was measured with neural imaging [12]. Additionally, the tranquility of natural places has been investigated and evaluated with established soundscape indicators [13]. Finally, tranquility is considered to be an important characteristic of the soundscape of religious spaces [14]. A study on linguistic representations of tranquility has been conducted among the French population [15; 16]. In this research, three major groups of people were identified: those who associate tranquility to social relationships, those that mention sounds, in particular natural sounds with relation to tranquility, and those that focus on silence. Although these categories were quantitatively assessed for \"_zones calmes_\" (quiet areas), there has been no attempt to relate these findings to the perception of the sonic environment. Therefore, linking these findings with widely used soundscape evaluation methods could provide new insights into the assessment of urban parks. In a broader context, this paper focuses on the influence of the viewpoints or beliefs related to tranquility and the way they affect the perception of the sonic environment. The present study combines a tranquility viewpoints extraction methodology with the soundscape perception data from questionnaires administered in urban parks, and aims to quantitatively and directly link this personal factor to the perception of the sonic environment in urban parks. Based on the theoretical consideration on the perception of soundscape given in [17], two hypotheses are formulated. A first hypothesis relates directly to attention mechanisms, the component of sensory processing that prioritizes on the basis of motivational relevance [18]. Known sounds trigger attention more than unknown sounds and a keen interest in these sounds may sustain voluntary attention to them. Thus, people associating tranquility to hearing specific sounds, in particular natural ones, may have a better knowledge and sensitivity for them and hence a higher probability for noticing these sounds. Moreover, it could also be expected that these people report hearing natural sounds more often when asked about their experience while visiting a park. Similarly, people that associate tranquility to social sounds could be expected to notice human voices more often.