It might be: "Hey, sweetheart!" Or maybe "Nice arse!" Things might get creepy: "Where are you going? Can I come with you?"

These are classic examples of catcalling - unwelcome sexual remarks or gestures from unknown men in a public space. It's something women experience every day - on the street, on the U-Bahn, in the supermarket. Research by Cornell University in the US has shown that 85 per cent of cat-calling victims had been harrassed for the first time before the age of 17.

Such unsolicited comments are not compliments. On the contrary - they scare you. American studies that investigated the effects of verbal abuse on victims' psychological wellbeing found that with increasing experiences of harrassment, feelings of body shame and fear of rape increase, while self-esteem decreases. Victims' sense of safety also diminishes.

A research group at the University of Mary Washington in Virgina also found that women experience "creeping trauma" as a result of frequent harassment. This is one reason why post-traumatic stress disorder is more frequently diagnosed in women than in men.

In Germany, the chance that women will suffer from it is almost twice as high as for men. Although women, unlike men, seldom take part in acts of war, they thus suffer more often from traumatic experiences. Constant unwanted advances and a permanently heightened awareness of danger are cited as explanations. 

Catcalling incurs a psychological burden and restricts women's mobility. Women will avoid certain places, constantly check their surroundings, adjust their clothes. And yet this everyday violence against women is legal in Germany. According to paragraph 184i of the German Penal Code, sexual harassment only occurs when "another person is physically touched in a sexually specific way and thereby harassed." Men who intimidate women with words and gestures, who invade their spaces, are abiding by German law.

The petition "It's 2020. Catcalling should be a crime" is trying to change that. Initiator Antonia Quell says: "Not every man does it, but every woman knows it." For her, catcalling is "the exploitation of dominance and power". More than 66,000 people have already backed her demands.

The issue is being addressed in other European countries. In Belgium, Portugal, the Netherlands and France, verbal harassment is illegal. Anyone who verbally assaults a woman in France could face a fine of up to €750.

The aim of such measures is to nip sexual violence in the bud. That begins with unwanted remarks.