Nails on a Chalkboard!

As part of an assignment for one of my classes, I was required to set up a small little booth out in public where I would have to find at least 25 strangers who would allow me to photograph them.  The concept that I came up with for this was based off of people's responses to the sound of nails scraping down a chalkboard.  This sound is known to be one of the most irritating (and, in some cases, physically painful) sounds that we know of, so I chose to use something so universally negative.  I asked the subjects to listen to a soft song while I took their pictures; however, ten seconds into the soothing music, I spliced a loud nails on a chalkboard sound effect to force a strong auditory response.  This was such a great experience, and I might consider continuing this endeavor to build an entire book out of it.  Hope you enjoy!