Most people don't think about their background noise levels, but those who work or live in noisy environments need to be aware of sounds that could ruin their hearing. If you have an iPhone or iPad, you can monitor your ambient noise levels using the new SoundMeter+ application.
SoundMeter+ uses the iPhone's internal microphone to measure the surrounding noise and calculate the dBA of your surroundings. You can also change the meter to measure dBC, dBB, dBD and dBZ. These different measurements take into account the different frequencies of sound. For example, the A-weighting (dBA) emphasizes those frequencies that the human ear can hear, while the B-weighting (dBB) takes into account lower frequencies and is used to measure entertainment noise.
The app shows a variety of information about your ambient sound levels. It displays a digital meter that gives you the exact dBA measurements and a graphical meter that shows how the noise fluctuates. It also keeps track of the max and min noise levels recorded by the app and the hold time for each one (i.e., how long each one lasted).
SoundMeter+ not only measures the live sound levels, it also analyzes your ambient noise over time. This information is then used to calculate the Time Weighted Average (TWA), which measures the different noise levels that a person is subjected to throughout a normal working day. This figure is most commonly used by OSHA to assess a worker's exposure to hearing-damaging sounds.
There's a lot of information packed into a very affordable US$1.99 app. My only quibble with the app is that it is not optimized for the iPhone 5. As a result, the meter only occupies two-thirds of the screen and the help file has too many blank spaces.
Disclaimer: I did not test the SoundMeter+ app against a noise dosimeter or any other professional sound-measuring equipment. I only compared SoundMeter+'s measured sound levels to known levels, and the app was accurate with its measurements. Also, the app only calculates the background noise so you can become more aware of situations that require some form of hearing protection. It is not meant to be used in the diagnosis or treatment of any medical conditions. It's also not meant to be used as legal evidence in workplace safety disputes.