How to add filters for the removal of noise from a recorded audio file in iOS

Question

I am making an iPhone app to record and play the human voice back just like Talking Tom . Everything works fine, but I am not able to figure out how do I remove the background noise in recorded audio file?

I know the low pass filtering is an option to do so, but I dont know how to code this? Can anyone help me to implement a low pass filter or something else to remove the background noise from a recorded audio file in iOS.

Answer 1

I don't do ios, but there is an example of a low pass filter for accelerometer for the iphone at Accelerometer Low Pass Filtering which you may be able to adapt for your use.

Basically the filtered value at time x = unfiltered value at time x * alpha + filtered value at time x-1 * (1- alpha)

And for the filtered value at time 0 = unfiltered value at time 0 * alpha (assumes that the unfiltered value at time -1 is 0)

You will need to set the alpha using trial and error. Perhaps somewhere in the range 0.01 to 0.1 might be useful.