measuring decibels with mobile phone - audio

Question

Good Evening to everybody!
i have the following trouble: i'm tryin to measure the decibels(of the voice) using the microphone of my mobile phone but dont know why it doesn´t work!!! any suggestions??thanks for help!!
The program is this:
`package com.dani;
import java.io.IOException;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.app.Activity;
import android.widget.TextView;
public class Pruebita2 extends Activity {
TextView TextView;
StringBuilder builder=new StringBuilder();
MediaRecorder mRecorder;
double powerDb;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.pruebita2);
TextView=new TextView(this);
setContentView(TextView);
mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
mRecorder.setOutputFile("/dev/null");
try {
mRecorder.prepare();
} catch (IllegalStateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
mRecorder.start();
}
public double getAmplitude() {
if (mRecorder != null)
return (mRecorder.getMaxAmplitude());
else
return 0;
}
powerDb = 20 * log10(getAmplitude() / referenceAmp);//obtain the DECIBELS
}`

Answer 1

this code works for me:
import android.app.Activity;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.widget.TextView;
public class Noise extends Activity {
TextView mStatusView;
MediaRecorder mRecorder;
Thread runner;
private static double mEMA = 0.0;
static final private double EMA_FILTER = 0.6;
final Runnable updater = new Runnable(){
public void run(){
updateTv();
};
};
final Handler mHandler = new Handler();
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.noiselevel);
mStatusView = (TextView) findViewById(R.id.status);
if (runner == null)
{
runner = new Thread(){
public void run()
{
while (runner != null)
{
try
{
Thread.sleep(1000);
Log.i("Noise", "Tock");
} catch (InterruptedException e) { };
mHandler.post(updater);
}
}
};
runner.start();
Log.d("Noise", "start runner()");
}
}
public void onResume()
{
super.onResume();
startRecorder();
}
public void onPause()
{
super.onPause();
stopRecorder();
}
public void startRecorder(){
if (mRecorder == null)
{
mRecorder = new MediaRecorder();
mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
mRecorder.setOutputFile("/dev/null");
try
{
mRecorder.prepare();
}catch (java.io.IOException ioe) {
android.util.Log.e("[Monkey]", "IOException: " +
android.util.Log.getStackTraceString(ioe));
}catch (java.lang.SecurityException e) {
android.util.Log.e("[Monkey]", "SecurityException: " +
android.util.Log.getStackTraceString(e));
}
try
{
mRecorder.start();
}catch (java.lang.SecurityException e) {
android.util.Log.e("[Monkey]", "SecurityException: " +
android.util.Log.getStackTraceString(e));
}
//mEMA = 0.0;
}
}
public void stopRecorder() {
if (mRecorder != null) {
mRecorder.stop();
mRecorder.release();
mRecorder = null;
}
}
public void updateTv(){
mStatusView.setText(Double.toString((getAmplitudeEMA())) + " dB");
}
public double soundDb(double ampl){
return 20 * Math.log10(getAmplitudeEMA() / ampl);
}
public double getAmplitude() {
if (mRecorder != null)
return (mRecorder.getMaxAmplitude());
else
return 0;
}
public double getAmplitudeEMA() {
double amp = getAmplitude();
mEMA = EMA_FILTER * amp + (1.0 - EMA_FILTER) * mEMA;
return mEMA;
}
}