FFT is a high-resolution audio analysis tool for the iPhone and iPod Touch. It uses the Fast Fourier Transform to analyze incoming audio, and displays a very detailed graph of amplitude vs. frequency.

This application has been designed for acoustics work, and so the bins have been normalized to octaves, to get a display that will show a flat line for pink noise. You can control both the level of graph smoothing and decay time, to get as much or as little detail as you require.

You can also control the dB resolution of the graph, as well as the frequency range that is displayed.

Included in this app is the engine from our Generator app, which is a low-distortion, artifact-free signal generator. The signal generator appears as a heads-up display when you tap the icon, so you can see the graph while you adjust the generator. Generate sine waves, square waves (within limits), white noise, and pink noise, optionally in psuedo-balanced mode. All waveforms are generated in real time using high-precision algorithms.

Move your finger across the screen to get a cursor to read out exact dB levels and frequencies.

Use a vertical pinch-open gesture to expand the dB scale.

Use a horizontal pinch-open gesture to expand the frequency scale.

Smooth the graph by octave, 1/3, 1/6, 1/12, or 1/24 octave. Adjust the decay time from 0.5 seconds, for a very fast fluid display, to 8 seconds, or use Peak Hold or Average mode. Average mode is a true equal-weighted average, which can run continuously.

*** NEW: Turn on Peak Tracking to have FFT automatically find a label the frequency of the highest peak on your graph.

Set the FFT size from 128 to 8192 points, or select Equal Points Per Octave mode, for high-resolution analysis, even at low frequencies.

FFT comes calibrated for the typical iPhone microphone, and you can adjust the calibration. In addition, you can select Internal or External mic. In Internal mode, a compensation filter is used to flatten the response of the built-in microphone. When you select External mode, the response is flat, and a separate calibration factor is used. External mode is used with a line input, or with our iPhone Measurement Mic (coming soon).

This application also supports psuedo-balanced output, where one channel is inverted in phase, to get a higher output level. Balanced Output mode is used with our balanced cable adapter.

When your analysis is complete, you can save the graph image to your photo roll to include in a report.

NOTE: FFT will run on a first generation iPhone, but we recommend using the headset mic, or our measurement mic, when available. The built-in mic can only run at a sample rate of 8000Hz, so there is much less resolution, and no information at all above 4000Hz.

See our web site for more detailed information.

Also, check out our other great audio and acoustics apps: SPL, LEQ, for recording SPL over time, RTA, ETC, RT60, Generator, and Speaker Pop.

And, if you are looking for a great range of high-quality, professional, audio test equipment, check out www.sencore.com. They sell the current versions of the Audio Toolbox, as the SoundPro line of audio test equipment.