A study of a number of Serbian Orthodox medieval churches, during their reconstruction or archeological investigation, revealed the presence of acoustical resonators. This paper offers a review of the resonators discovered to date. In addition, laboratory experiments were conducted on several resonators removed from churches in order to clarify their function. Based on the relevant literature, laboratory experiments, and analyses of acoustical characteristics of the worship spaces where resonators were found, it is concluded that the resonators found in medieval Serbian churches have not contributed to their acoustic quality. There are three reasons why the resonators were not effective. They were installed in very small churches where the additional absorption is not significant, their resonant frequencies were too low in relation to the frequency content of Serbian Orthodox worship service, and lastly, in some cases there were too few resonators to achieve audible changes in acoustic response of the church.
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