iApps for Everything

Includes Octave and 1/3 Octave modes, with selectable decay times, as well as Peak Hold and true linear Average mode.

Also includes a built-in pink noise generator. Flip the screen over, turn on pink noise, and plug a cable into the headphone connector (use a mic splitter) to generate full-band pink noise. Pink noise is equal energy per octave, and so will appear flat on the RTA display if the system response is flat. See our web site for more information.

*** NEW — in this version, you can save and recall up to ten graphs, marked with the date & time and your comment, as well as store the image to your photo roll.

You can also turn on resettable Max/Min bars (see image #4) to capture peaks. Double-tap to reset the bars.

RTA uses a special frequency-compensation filter to flatten the iPhone mic. Make sure you select Internal on the setup page.

RTA is designed by the same team that built the Audio Toolbox acoustic analyzer.

The internal iPhone mic has a noise floor near 30 dB, and clips around 105 dB. So, be aware that this tool will NOT work in very loud environments, such as clubs or some concerts. RTA will work on first-generation iPhone, but always use the headset mic, as the built-in mic runs at a low sample rate.

If you have an iPod Touch 2nd generation, use a headset mic, and if you have a first generation iPod Touch, you must use one of the dock-connector microphones and be running OS 2.2 or later.

Fully interactive touch GUI features includes scroll up/down, pinch to zoom or compress the vertical dB scale, or swipe horizontally to get a cursor that reads out the exact dB level and frequency across the screen. To make the cursor disappear, swipe it off the graph to the left.

The landscape-mode display flips 180 degrees so that you can face the internal mic in either direction.

Also included are optional noise curve overlays, in NCB, RC, PNC, and NR mode. See picture #2 for an example. Use this feature to get a quick reading on the noise levels in a room. Also includes the cinema large-room X-curve overlay.

RTA can be calibrated, and stores two calibration constants, one for the internal mic and one for the external calibrated test microphone. We even have corrected for the iPhone’s intrinsic high and low-frequency roll-offs.

NOTE: I have enabled purchasing for first gen Touch, but please realize that it has no normal mic or support for a headset mic; you will have to use a 3rd party mic that uses the dock connecter, or wait for our measurement mic.

See our other acoustics and audio apps, LEQ, for recording SPL over time, SPL, the professional Sound Level Meter for the iPhone, ETC, the Energy Time Curve app, Generator, the iPhone signal generator, FFT, for detailed acoustic analysis, RT60, to measure decay time, and Speaker Pop, which tests speaker polarity.

And don’t miss our new SPL Meter app — a faithful reproduction of a classic analog sound level meter.