Decibel is a free iPhone app developed by Paula Jeff in the Utilities & Tools category. It serves as a sound level meter, allowing users to evaluate the noise around them. With Decibel, users can measure the sound pressure and compare their recordings to the reference chart included in the app.

The app offers a range of features, but to access them, users need to subscribe. These features include saving audio recordings and having an active screen that displays the history of audio recordings. This can be useful for monitoring and analyzing sound levels over time.

Overall, Decibel provides a convenient tool for assessing noise levels in various environments. Whether you want to measure the sound of a normal conversation, a diesel truck, or even a rocket launch, this app can help you gauge the decibel levels accurately.