Question: Just wondering how easy to do something like this in Iphone.

will Like to how to make the needle move

Thanks for reading and comments

![enter image description here](https://i.stack.imgur.com/KfCjP.jpg)

Answer: 
Very easy if you know what you're doing - apply A-weighting filter, RMS, apply time weighting filter, convert to dB. The major problem is calibrating the microphone.

However, if you haven't done audio processing with biquads before and you don't know anything about it, it's probably not that easy.
It depends how much experience you have in objc :)
But representing analog value with a gauge like this
is not too complicated. 

[This](http://www.cimgf.com/2008/10/25/core-animation-tutorial-slider-based-layer-rotation/) link for example should get you started...