Bird strikes with man-made structures and vehicles cost the lives of millions of birds globally. Despite of the perfect visual abilities of most bird species many of them are sensitive and often collide with operational wind turbines. For this reason, we set out to test and calibrate a custom-made sound capable of successfully deterring birds from a given zone. We have investigated the behavioural response of birds when subjected to this specific sound, designed to induce an innate acoustic startle reflex (ASR) reaction but no stress. A special ASR signal was previously shown to have permanent effect on bird behaviour without inducing the production of cortisol – the stress hormone. We have modified the sound in order to test both the behavioural and physiological responses of great reed warblers (Acrocephalus arundinaceus). The study took place between July 6th 2020 – July 11th 2020 at “Kalimok” biological station – part of the Institute of Biodiversity and Ecosystem Research (IBER) at the Bulgarian Academy of Sciences (BAS). The experiment design and its implementation followed all methodological requirements for experimental studies on birds. Tests were performed in 20cm x 40cm cages and the birds’ behavior was recorded using cameras. The behavioural response of each bird was quantified and analyzed using behavioral ethograms and a strength of reaction scale from 1 to 5.