The sonic environment is an invisible but crucial part of the urban environment. Increasing density of population and diversification of social functions driven by urbanization lead to a more complex sound environment in our daily life. As an important multifunctional service area, the urban park is usually regarded as a buffer for urban noise pollution. The assessment of the sonic environment in urban parks can help park-users and park-designers get a better understanding of the health of the park environment. This study approached the urban noise pollution in urban parks with a soundscape quality assessment, from both acoustical and psychological perspectives. An urban park on the campus of the University of Pennsylvania named Penn Park was selected as a case study for soundscape quality assessment. Sound Pressure Level (SPL) was measured at ten sampled positions in Penn Park and processed in ArcMap to make the sound maps, which clearly shown the uneven distribution of the average sound energy in the park: inner part of the park with trees surrounded was the “quietest” and the part along the edge with areas of grass was the “loudest.” In three months (May, June, July) when sound pressure level was recorded by the sound pressure meter, park-users’ subjective responses to the sonic environment of Penn Park were investigated by randomly recruiting park visitors to complete a questionnaire about the soundscape quality. In total, 90 questionnaires were collected and analyzed on SPSS. Results demonstrated that there was a significant positive correlation between overall landscape quality, overall soundscape quality, and overall impression. Compared to mechanical sounds and human-made sounds, visitors preferred more natural sounds (birds, insects, wind) to be increased in Penn Park. Overall, the sonic environment of Penn Park was perceived as pleasant, quiet, smooth, varied, calming, directional, natural, and steady. The results of this study may have implications for the enhancement of soundscape design in other urban parks that are similar to Penn Park.