Portrait View
Controls View
Soundview

For iPhone & iPod Touch.
Sound View is a Audio Spectrum Analyzer App for the iPhone 3GS & iPhone 4, and iPod Touch 3G ( with external microphone ). It also runs well on an iPad in compatibility mode. It analyzes sound from the iPhone built in microphone, or from an attached external microphone, and displays both the input signal, and the results of the spectrum analysis. The input signal is displayed in the lower view as a waveform and the spectrum is displayed in the upper view as bars indicating the strength of that frequency within the input signal.
Both portrait and landscape mode are supported. Portrait mode includes a frequency scale at the bottom of the view, which represents 1/2 of the sampling rate. The sampling rate is 44100 samples per second, the same as a Compact Disc.
Landscape View
By selecting the info button, next to the app title, the Settings view appears. If you turn off, Enable Waveform, and hit the info button once more, you will see the Spectrum Control view on the bottom of the screen. From here you can turn on or off the audio filter. The filter averages 7 full spectrum samples and removes those averages from the output. This allows some background noise to be removed from the display. The resample button allows you to control what gets sampled as background noise.
The magnification slider allows you to control height of the spectrum analyzer bars. Depending on the number of bars configured via the settings view, each spectrum bar represents a different number of frequencies, and therefore its value varies with the number of spectrum bars. Ideally the spectrum bar height would indicate the decibel level of that frequency, however each bar represents a range of frequencies, and it's value is a sum of their decibel levels.
The decay rate slider allows you to control how fast the bars fall back to the bottom of the display. The control gives you full control, as the far left will let the value bar fall immediately, and the far right will not allow it to fall at all.