It’s not the value of the dollar; that graph is charting live audio.

SignalScope is a real-time signals analysis program that displays information about the structure of sound. Audio/video professionals, musicians, engineers, and scientists could use it to measure frequency, waveform, and other audio attributes, displaying that data in graphs on the iPhone. When measuring audio playback from a speaker installation, for example, a pro could tweak treble and bass so music in that specific room mirrors the room acoustics of the original recording. However, SignalScope is stuck in an uncomfortable middle ground; it's too expensive for casual users, but it's too flawed for professional or semi-pro use.

SignalScope looks great. Some of its features, such as a button that freezes and unfreezes the real-time display, are slick. This toggle lets you take a closer look at an intermittent sound.

The problem is that SignalScope's essential functions are cumbersome and unpleasant. It feels like it just hasn't been tested enough in the field. For instance, zooming and scrolling the spectrum and waveform charts requires you to make pinch gestures on the tiny chart labels, which the interface turns into an awkward, error-prone process. The iPhone's auto-rotating screen becomes a nuisance in real-world use. Peak detection often fails, and the labels have occasional visual glitches. Also, SignalScope only samples at 8kHz through the original iPhone's internal mic, so you'll need a headset or a professional-grade microphone. (3G iPhones support 48kHz.)