Nothing seems more annoying that the sound of fingernails running down a chalkboard. Well, maybe the sound of a fork scraping a ceramic plate.

New research from the Macromedia University for Media and Communication in Germany and the University of Vienna suggests that the reasons most of us are painfully peeved by these high-pitch squeals is both physical and psychological.

Research participants were exposed to the sound of nails on a chalkboard and similar sounds, such as a fork scraping a plate. Some were told the sound was part of a musical piece, while others were told the truth. The researchers measured the physical reactions of participants, such as their heart rate and blood pressure, while they were listening to the sound. Then, the participants were asked to rate how pleasant or unpleasant the noise sounded.

Those who were told the sound was a piece of music were more likely to rate the noise as less unpleasant, compared to those who knew the true source of the sound. According to researchers, these findings suggest that part of the annoyance to these noises might partly be in your head. But there’s also a physiological component to the displeasure.

The sound pitch, which typically hits between 2,000 and 4,000 hertz, is naturally amplified by the shape of human ear canals, according to researchers. Most of the participants, regardless of how they rated the sound, exhibited higher heart rates and blood pressure to some of the sounds.

Their findings will be presented at the Acoustical Society of America annual meeting in San Diego this week.

Previous research thought these sounds were so maddening because they are similar to primate warning calls. But that theory didn’t stick. Others had trouble nailing down what sound frequencies seemed to be about the most irritating.

Researchers say they can now pinpoint what’s so darn annoying about nails on a chalkboard and similar sounds.

Blame the ear canal. Blame the preconceived notions that we should be annoyed by the squeaks and squeals.