iTestMic plugs directly into the 30-pin connector, and is powered from the iOS device. It auto-calibrates, uses very little power, and provides excellent performance. Upgrade your AudioTools app to accurately test and setup subwoofers, measure much lower noise levels, and measure sound levels up to 120 dB SPL. When you plug iTestMic into any iOS device running AudioTools, the factory calibration values are read and applied, giving you an instantly available accurate SPL measurement tool calibrated to +/-0.1 dB, no matter what iOS device you are using. Small enough to keep in a pocket or backpack, for quick and accurate sound measurements, and always available.