What was that?

With this project I wanted my audience/victims to be unnerved; I wanted to induce the "goosebumps" experience, so to speak, where something feels strange and a little upsetting, but not overtly. My solution was to play an unexpected sound in an innocuous situation. To do this, I recorded a li'l sumthin (the exact recording was a mixture of knocking, sniffles, and a girl saying "Hello?" and "Help me...") and made it into a ringtone; then I hid my phone somewhere close to where my classmates would be and triggered the sound by calling my phone. I assigned two of my classmates to a paper airplane competition, and I triggered the sound while they were folding.

When these two heard the sound, one looked up briefly and returned to his task, and the other said something like "what's that sound?" but ultimately also returned to folding his paper airplane. There was some reaction from the rest of the class as well, along the same vein. Someone suggested an origin for the sound, but as I kept playing it everyone seemed to dismiss it. 

All in all, I would say this project was maybe 60-75% successful; under more of an everyday situation, I believe I might have been able to elicit more of the reaction I wanted. While people did seem to be startled by the sound, I don't think anyone was particularly disturbed by it. At the end, my two participants said that upon hearing the recording for a while they had both come up with what seemed to be a plausible explanation for it.

To improve within the same classroom context, someone suggested that I could've talked with the instructor beforehand and arranged to have the sound played during class itself. Of course, this probably would've had the best effect if it were simply placed somewhere slightly isolated and motion activated.