Georgia State University
Georgia State University: Hyper Physics: Pitch = Frequency of Sound
Pitch is the ear's response to frequency, and here you can get a better understanding of pitch, its measurement and the perception of pitch.
Other
Manchester Museum of Science and Industry: Sound 101: Bad Vibes
Learn about sounds and rate sounds from just "bad" to "really horrible." Then read an explanation about acoustics and the reason why people find some sounds to be worse than others. Also learn to mix your own sounds.