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.
*** IMPORTANT NOTE ***
If you are planning on buying iAudioInterface, you should buy our AudioTools suite of apps instead of this app, and then buy this module as an in-app purchase. Also, this module is discounted in AudioTools.
*** NOTE TO iPhone 3GS USERS ***
We have determined that the internal microphone, as well as any mic that is plugged into the headset connector, has a much steeper low-frequency roll-off than previous iPhone models. We have corrected for this in this release, however, low frequency analysis on this device will have less accuracy than other iPhone and Touch models.
*** Designed for Acoustical Analysis
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.
*** Includes Signal Generator
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.
*** Cursor Readout
Move your finger across the screen to get a cursor to read out exact dB levels and frequencies.
*** Touch-GUI Controls
Use a vertical pinch-open gesture to expand the dB scale.
Use a horizontal pinch-open gesture to expand the frequency scale.
*** Graph Smoothing
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.
*** Peak Tracking
Turn on Peak Tracking to have FFT automatically find a label the frequency of the highest peak on your graph.
*** Tune the Parameters
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).
*** Save and Recall
When your analysis is complete, you can save the graph image to your photo roll to include in a report.
*** Display Multiple Graphs
Show a recalled graph on the screen in a different color.
*** Difference Mode
Use a stored graph as a baseline that is subtracted from the current graph in real time.
*** RTA or FFT?
If you are wondering if you should download this app or our FFT app, check out our website, we have a page devoted to this topic.
*** Other Audio Apps
Also, check out our other great audio and acoustics apps: AudioTools, our premier suite of audio and acoustics analysis apps, SPL, SPL Graph, for recording SPL over time, RTA, RT60, Generator, and Speaker Pop.