When using AVFoundation, you’ll notice that the numbers returned when checking the audio channel power levels may look kind of strange. The audio levels returned to you when calling AVCaptureSession-averagePowerLevel or AVCaptureAudioChannel-averagePowerLevel, etc. are in a logarithmic scale from -160dB to 0dB, similar to how we perceive sound.

But you may want to convert this logarithmic scale to a linear scale from 0.0 to 1.0 to use in an interface or something, here’s how to do it:

CGFloat linearPowerLevel = powf(10.f, decibelPowerLevel / 20.f);

Here’s how to go the other way:

CGFloat decibelPowerLevel = log10f(linearPowerLevel) * 20.f;