Do not underestimate the entertainment value of a real-time spectrogram on your iPhone/iPad… This free app by Oxford Wave Research takes advantage of the iPhone/iPad’s built-in microphone to provide a color-coded spectrogram that allows one to compare the sound signatures of the subway on the way to work, the birds chirping in the park, the loud centrifuge in the corner of the lab… Well, you get the idea. Despite its innate entertainment value, this spectrogram and spectrum analyzer can certainly be used for more serious endeavors as well. The settings panel allows one to adjust the audio sample rate and the fast Fourier transform order (and the information tab explains what both of those things are). I just wish that there was a way to save/export the traces.