Playing an Arbitrary tone with Android?

This example demonstrates how do I playing an arbitrary tone with android.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:gravity="center"
   android:orientation="vertical"
   android:padding="16dp"
   tools:context=".MainActivity">
   <ImageView
      android:layout_width="200dp"
      android:layout_height="300dp"
      android:src="@drawable/ic_music_note_black_24dp"/>
   <TextView
      android:text="Increase the emulator Volume, Listen to the arbitrary tone!"
      android:textSize="16sp"
      android:textStyle="bold|italic"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"/>
</LinearLayout>

Step 3 − Add the following code to src/MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.os.Bundle;
import android.os.Handler;
public class MainActivity extends AppCompatActivity {
   private final int duration = 10;
   private final int sampleRate = 8000;
   private final int numSamples = duration * sampleRate;
   private final double[] sample = new double[numSamples];
   private final byte[] generatedSnd = new byte[2 * numSamples];
   Handler handler = new Handler();  
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
   }
   @Override
   protected void onResume() {
      super.onResume();
      final Thread thread = new Thread(new Runnable() {
         public void run() {
            genTone();
            handler.post(new Runnable() {
               public void run() {
                  playSound();
               }
            });
         }
      });
      thread.start();
   }
   void genTone(){
      for (int i = 0; i < numSamples; ++i) {
         double freqOfTone = 440;
         sample[i] = Math.sin(2 * Math.PI * i / (sampleRate/ freqOfTone));
      }
      int idx = 0;
      for (final double dVal : sample) {
         final short val = (short) ((dVal * 32767));
         generatedSnd[idx++] = (byte) (val & 0x00ff);
         generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
      }
   }
   void playSound(){
      final AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
      sampleRate, AudioFormat.CHANNEL_OUT_MONO,
      AudioFormat.ENCODING_PCM_16BIT, generatedSnd.length,
      AudioTrack.MODE_STATIC);
      audioTrack.write(generatedSnd, 0, generatedSnd.length);
      audioTrack.play();
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
         <activity android:name=".MainActivity">
            <intent-filter>
               <action android:name="android.intent.action.MAIN" />
               <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
         </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from the android studio, open one of your project's activity files and click the Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen −