At the very least this is harassment. It is actually sexual harassment, but, sexual harassment is normally thought of as confined to the job. When a woman is followed it is stalking.
A person feels intimidated or uncomfortable is the definition of sexual harassment. In the work place it is believed to effect job performance.
Perhaps a better way of classifying this is social harassment.
It is known that sexual harassment can cause post-traumatic stress disorder, high blood pressure, sleep problems, physical pain, depression and suicide.
Perhaps the best way of classifying the behavior of these men is bullying. Bullying is an act of intentionally inflicting injury or discomfort upon another person through physical contact, through words or in other ways, repeatedly and over time for the purpose of intimidation and/or control.
Aren't the men seeking control? Their cat calls have a purpose. What is that purpose? It isn't compliments because that would indicate respect. Cat calls are not respect. The purpose of cat calls is to bring attention to the man who is seeking to control the outcome of the woman walking through his territory.
Cat calls make women feel uncomfortable, unsafe and makes the impression to change the place where she walks. She may feel the need to instead take a taxi. The burden in on the woman to carry the responsibility for men's bad behavior. When a woman feels unsafe she modifies her behavior to protect herself.