Android, How to use microphone in order to calculate sound frequencies?

Question

I'm working on Audio tuner application in order to tune musical instruments. User should play a note, then in my application I should show which frequency it has.

The first, I should access to microphone?

AudioRecord recorder = new AudioRecord(MediaRecorder.AudioSource.MIC,
sampleRate, AudioFormat.CHANNEL_IN_STEREO,
AudioFormat.ENCODING_PCM_16BIT, bufferSize);

Then I need to calculate frequency of sound. How can I do this?

Solution

I'm also trying to do this. I haven't managed it myself yet, as I'm completely new to android development, but here are two useful links to the source code of other tuners, one in Java, one not:

• http://www.psychicorigami.com/2009/01/17/a-5k-java-guitar-tuner/
• http://www.codeproject.com/Articles/32172/FFT-Guitar-Tuner

EDIT: Thought I better link to the MANY alternatives on this site with people trying to make a guitar tuner.

• How to create tuner that runs continuously?
• Sound convertion to frequency in android
• Real time pitch detection

RE-EDIT: FFT.java

Solved my problems. (Not linked properly because I'm a new user)