In Philadelphia the city has installed high pitched noise makers that turn on after 10:00 pm to deter teenagers from hanging out there late at night. It's controversial because some think it discriminates against the teens.

The noise can usually only be heard by people who are 25 years-old and younger, since our hearing naturally deteriorates as we age. Some people who are older can still hear it, but generally people much older than 25 won't be able to hear this high frequency.

Here is where you can hear the sound, it's about 30 seconds into the story, or you can download it here.

The picture below is a visual representation of that high pitched noise. That peak my finger is pointing at is the noise.

Andy Erickson/Hot 104.7

When we played it in our studio, without radio processing which alters the frequencies of all audio played, I could not hear it at all and Natasha not only heard it but said she felt it, like it was compressing her head.

There's a company that sells the devices that are installed and emit the sound to repel young ruffians.