[android-developers] Re: Recorded voice is very very low and lot of noise is recorded.

Hi,
The human voice frequency is between 60Hz to 7 KHz see :
http://en.m.wikipedia.org/wiki/Human_voice
The nyquist-Shannon theorem says that the sampling rate need to be AT
LEAST twice as the maximum frequency of the original signal :
http://en.m.wikipedia.org/wiki/Nyquist–Shannon_sampling_theorem which
mean that a sampling rate of 8 KHz will only allow you to record
frequencies below 4 KHz which are low frequencies.
In order to hear human voice you would need to sample your recording
at 16 KHz.
Please that the industrial recording frequency is 44.1 KHz.
Regards,
Julien-François COLLIN
On 16 sep, 19:30, niko20 <nikolatesl...@yahoo.com> wrote:
> You definitely need to use a higher sample rate. At 8Khz it will sound
> like talking through a phone - very noisy.
>
> -niko
>
> On Sep 15, 3:51 am, Harpreet <harpreetsingh.ja...@gmail.com> wrote:
>
>
>
> > Hello everybody
>
> > Any thought?
>
> > On Sep 13, 9:19 pm, harpreet singh <harpreetj...@gmail.com> wrote:
>
> > > Hi,
>
> > > I am trying to record the voice using AudioRecord class and writing
> > > the read bytes to speaker using AudioTrack class. I am able to hear
> > > the voice coming from Speaker but the voice is very low and a lot ofnoiseis coming along with the recorded voice.
>
> > > Any solution to resolve this problem to reduce thenoiseand loud the
> > > actual voice.
>
> > > I am using below code for this:
>
> > > package com.my.mic.record;
>
> > > import android.media.AudioFormat;
> > > import android.media.AudioManager;
> > > import android.media.AudioRecord;
> > > import android.media.AudioTrack;
> > > import android.media.MediaRecorder;
> > > import android.util.Log;
>
> > > public class Record extends Thread
> > > {
>
> > >         int numCrossing,p,numSamples,af;
>
> > >         static final int bufferSize = 200000;
> > >         short[] buffer = new short[bufferSize];
> > >         short[] readBuffer = new short[bufferSize];
> > >         boolean isRecording;
> > >         AudioManager am;
>
> > >         public AudioRecord arec;
> > >         public AudioTrack atrack;
>
> > >         private int sampleRate = 8000;
>
> > >         public void run() {
>
> > >                 isRecording = true;
>
> > > android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URG ENT_AUDIO);
>
> > >                 int buffersize =
> > > AudioRecord.getMinBufferSize(sampleRate,AudioFormat.CHANNEL_CONFIGURATION_M ONO,
> > > AudioFormat.ENCODING_PCM_16BIT);
>
> > >                 arec = new
> > > AudioRecord(MediaRecorder.AudioSource.MIC,sampleRate,AudioFormat.CHANNEL_CO NFIGURATION_MONO,AudioFormat.ENCODING_PCM_16BIT,
> > >                                 buffersize);
>
> > >                 //buffersize = arec.getMinBufferSize(arec.getSampleRate(),
> > > arec.getChannelConfiguration(), arec.getAudioFormat());
>
> > >                 atrack = new
> > > AudioTrack(AudioManager.STREAM_MUSIC,arec.getSampleRate(),arec.getChannelCo nfiguration(),arec.getAudioFormat(),
> > >                                 buffersize,AudioTrack.MODE_STREAM);
>
> > >                 am.setRouting(AudioManager.MODE_NORMAL,AudioManager.ROUTE_EARPIECE,
> > > AudioManager.ROUTE_ALL);
> > >                 //am.setMode(AudioManager.MODE_NORMAL);
>
> > >                 Log.d("SPEAKERPHONE", "Is speakerphone on? : " +
> > > am.isSpeakerphoneOn());
>
> > >                 atrack.setPlaybackRate(sampleRate);
>
> > >                 byte[] buffer = new byte[buffersize];
> > >                 arec.startRecording();
> > >                 atrack.play();
> > >                 //atrack.setStereoVolume(atrack.getMaxVolume(),
> > > atrack.getMaxVolume());
>
> > >                 final float frequency = sampleRate;
> > >         float increment = (float)((2*Math.PI) * frequency / 44100); //
> > > angular increment for each sample
> > >         float angle = 0;
> > >         //AndroidAudioDevice device = new AndroidAudioDevice( );
>
> > >                 while(isRecording) {
>
> > >                         try {
>
> > >                                 arec.read(buffer, 0, buffersize);
> > >                                 atrack.write(buffer, 0, buffer.length);
>
> > >                         } catch (Exception e) {
> > >                                 Log.d("Record", ""+e);
> > >                         }
> > >                 }
>
> > >                 arec.stop();
> > >                 atrack.stop();
> > >                 //device.releaseTrack();
> > >                 isRecording = false;
> > >         }
>
> > >         public boolean isRecording() {
> > >                 return isRecording;
> > >         }
>
> > >         public void setRecording(boolean isRecording) {
> > >                 this.isRecording = isRecording;
> > >         }
>
> > >         public AudioManager getAm() {
> > >                 return am;
> > >         }
>
> > >         public void setAm(AudioManager am) {
> > >                 this.am = am;
> > >         }
>
> > >         public void stopRecording(){
> > >                 arec.stop();
> > >         arec.release();
> > >         atrack.stop();
> > >         atrack.release();
> > >         arec=null;
> > >         atrack=null;
> > >         setRecording(false);
> > >         this.stop();
> > >         }
>
> > > }

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