iPhone mic Frequency Compensation Filter: 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.

Specifications and Devices: 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.