Excessive dog barking is among the leading sources of noise pollution world-wide; however, the reasons for the annoyance of barking to people remained uninvestigated. This paper's questions were: is the annoyance rating affected by the acoustic parameters of barks; does the attributed inner state of the dog and the nuisance caused by its barks correlate; does the gender and country of origin affect the subjects’ sensitivity to barking. Participants from Hungary (N = 100) and Brazil (N = 60) were tested with sets of 27 artificial bark sequences. Subjects rated each bark according to the inner state of the dog and the annoyance caused by the particular bark. Subjects from both countries found high-pitched barks the most annoying: however, harsh, fast-pulsing, low-pitched barks were also unpleasant. Men found high-pitched barks more annoying than the women did. Annoyance ratings showed positive correlation with assumed negative inner states of the dog, positive emotional ratings showed negative correlation with the annoyance level. This is the first indication that acoustic features that were selected for effective vocal signalling may be annoying for human listeners. Among the explanations for this effect the role of affective communication and similar bioacoustics of particular animal vocalizations and baby cries are discussed.