how to convert level meter to Hz in iPhone?

Question

I'm using AudioQueue to get recording level meter via microphone. The problem is what I got from it are floating point numbers. I know they represents for audio sample.

I need to convert it to Hz. My assignment is to convert a digital signal audio recording from microphone. Convert it to Hz and do a simple formula to get a result that relevant to this number.

Please help, I really appreciate your help.

Thanks,

Quan

Answer 1

An audio recording from a microphone will not contain a single frequency that you can represent in Hz.

Instead, it will be a combination of a lot of different frequencies mixed together, which are represented by your samples.

To get the frequencies in your sample and their amplitude, you need to use the Fast Fourier transform. From the results you can determine which frequencies are most prevalent in your sample, which I believe is what you are looking for.