http://www.faberacoustical.com/products/iphone/soundmeter/

FEATURES

* Measure time-weighted and equivalent sound levels.
* Employ Flat, A, or C frequency weighting.
* Time-weighted measurement options include Fast, Slow, and Impulse weightings.
* Keep track of peak and maximum sound levels.
* Save high-resolution sound level display images to the iPhone’s Camera Roll photo album. Descriptive text may be added to the image before it is saved.
* Calibration controls enable automatic calibration, relative to a calibrated sound level meter, or manual entry of the microphone sensitivity.
* SoundMeter supports rotating the iPhone upside down, so the built-in microphone sits on top of the device when measuring sound levels.
* With the iPhone’s built-in microphone, SoundMeter can measure peak sound levels of up to approximately 105 dB. With the iPhone’s included headset microphone, SoundMeter can measure peak sound levels of up to approximately 100 dB.

Vía: Madridsoundscape.org