From Darren Gates:
This application is an advanced decibel (SPL) meter, with not only the ability to measure environmental sound levels, but also to SAVE those sound levels, with descriptions and time stamps, so that you can reference them and compare them later.This decibel meter has been calibrated against an actual Extech 407730 Digital SPL meter, using an iPhone 4. If you have another iPhone, or an iPod Touch with an external microphone, you may need to calibrate the app so that it reflects more accurate dB values.iPod Touch users: An external microphone is REQUIRED for this app to work. iPhone users have a microphone built-in to the hardware.Features include:- Graphical screen that shows the dB levels over a short period of time, so that you can compare the relative height of peaks and valleys.- Six common sound measurements, including: Average, Minimum, Maximum, Peak, Peak Hold, and of course the weighted dB level itself.- Meter-like screen that shows the dB reading in a display resembling an odometer.- Settings panel that includes: Weighting (A vs. C), Internal/External mic options, Trim (to adjust to different microphone sensitivities), and sampling rate to sample more or less frequently.- Save screen allows you to save a "snapshot" of the decibel meter values at any given moment, and even RECORD the ambient sound for later playback. You can later playback the audio sample, input some text describing what was recorded, and save the date/time of the recording. These are limited to about 30 seconds, and you have 10 available recording slots.Sampling Rate: This lets you change between slower and faster response times. A higher sampling rate yields a faster response time, which can be used to capture sudden peaks. Lower sampling rates give you a steadier view of the changing dB levels. In most situations, a SLOW response time will be more appropriate (smaller sampling rate).A Weighting vs. C Weighting: C Weighting is used most often in the sound analysis of machinery, car engines, and other noise that has a more consistent sound, whereas A Weighting is used for ordinary environmental noise measurements. The Info screen assumes A Weighting in its values.The Info screen gives you some sense of what the dB values correlate to in real live. This makes the application more helpful in an educational context.