diff --git a/src/com/android/server/telecom/RingbackPlayer.java b/src/com/android/server/telecom/RingbackPlayer.java
index a8af3ac..e0c6136 100644
--- a/src/com/android/server/telecom/RingbackPlayer.java
+++ b/src/com/android/server/telecom/RingbackPlayer.java
@@ -19,6 +19,7 @@
 import static com.android.server.telecom.LogUtils.Events.START_RINBACK;
 import static com.android.server.telecom.LogUtils.Events.STOP_RINGBACK;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.Preconditions;
 import android.telecom.Log;
 
@@ -42,8 +43,12 @@
      */
     private InCallTonePlayer mTonePlayer;
 
-    RingbackPlayer(InCallTonePlayer.Factory playerFactory) {
+    private final Object mLock;
+
+    @VisibleForTesting
+    public RingbackPlayer(InCallTonePlayer.Factory playerFactory) {
         mPlayerFactory = playerFactory;
+        mLock = new Object();
     }
 
     /**
@@ -52,25 +57,27 @@
      * @param call The call for which to ringback.
      */
     public void startRingbackForCall(Call call) {
-        Preconditions.checkState(call.getState() == CallState.DIALING);
+        synchronized (mLock) {
+            Preconditions.checkState(call.getState() == CallState.DIALING);
 
-        if (mCall == call) {
-            Log.w(this, "Ignoring duplicate requests to ring for %s.", call);
-            return;
-        }
+            if (mCall == call) {
+                Log.w(this, "Ignoring duplicate requests to ring for %s.", call);
+                return;
+            }
 
-        if (mCall != null) {
-            // We only get here for the foreground call so, there's no reason why there should
-            // exist a current dialing call.
-            Log.wtf(this, "Ringback player thinks there are two foreground-dialing calls.");
-        }
+            if (mCall != null) {
+                // We only get here for the foreground call so, there's no reason why there should
+                // exist a current dialing call.
+                Log.wtf(this, "Ringback player thinks there are two foreground-dialing calls.");
+            }
 
-        mCall = call;
-        if (mTonePlayer == null) {
-            Log.i(this, "Playing the ringback tone for %s.", call);
-            Log.addEvent(call, START_RINBACK);
-            mTonePlayer = mPlayerFactory.createPlayer(InCallTonePlayer.TONE_RING_BACK);
-            mTonePlayer.startTone();
+            mCall = call;
+            if (mTonePlayer == null) {
+                Log.i(this, "Playing the ringback tone for %s.", call);
+                Log.addEvent(call, START_RINBACK);
+                mTonePlayer = mPlayerFactory.createPlayer(InCallTonePlayer.TONE_RING_BACK);
+                mTonePlayer.startTone();
+            }
         }
     }
 
@@ -80,19 +87,27 @@
      * @param call The call for which to stop ringback.
      */
     public void stopRingbackForCall(Call call) {
-        if (mCall == call) {
-            // The foreground call is no longer dialing or is no longer the foreground call. In
-            // either case, stop the ringback tone.
-            mCall = null;
+        synchronized (mLock) {
+            if (mCall == call) {
+                // The foreground call is no longer dialing or is no longer the foreground call. In
+                // either case, stop the ringback tone.
+                mCall = null;
 
-            if (mTonePlayer == null) {
-                Log.w(this, "No player found to stop.");
-            } else {
-                Log.i(this, "Stopping the ringback tone for %s.", call);
-                Log.addEvent(call, STOP_RINGBACK);
-                mTonePlayer.stopTone();
-                mTonePlayer = null;
+                if (mTonePlayer == null) {
+                    Log.w(this, "No player found to stop.");
+                } else {
+                    Log.i(this, "Stopping the ringback tone for %s.", call);
+                    Log.addEvent(call, STOP_RINGBACK);
+                    mTonePlayer.stopTone();
+                    mTonePlayer = null;
+                }
             }
         }
     }
+
+    public boolean isRingbackPlaying() {
+        synchronized (mLock) {
+            return mTonePlayer != null;
+        }
+    }
 }
\ No newline at end of file
diff --git a/tests/src/com/android/server/telecom/tests/RingbackPlayerTest.java b/tests/src/com/android/server/telecom/tests/RingbackPlayerTest.java
new file mode 100644
index 0000000..f69d532
--- /dev/null
+++ b/tests/src/com/android/server/telecom/tests/RingbackPlayerTest.java
@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.telecom.tests;
+
+import static org.junit.Assert.assertFalse;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.when;
+
+import android.test.suitebuilder.annotation.SmallTest;
+
+import com.android.server.telecom.Call;
+import com.android.server.telecom.CallState;
+import com.android.server.telecom.InCallTonePlayer;
+import com.android.server.telecom.RingbackPlayer;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import org.mockito.Mock;
+
+import java.util.concurrent.CountDownLatch;
+
+@RunWith(JUnit4.class)
+public class RingbackPlayerTest extends TelecomTestCase {
+    @Mock InCallTonePlayer.Factory mFactory;
+    @Mock Call mCall;
+    @Mock InCallTonePlayer mTonePlayer;
+
+    private RingbackPlayer mRingbackPlayer;
+
+    @Before
+    @Override
+    public void setUp() throws Exception {
+        super.setUp();
+        when(mFactory.createPlayer(anyInt())).thenReturn(mTonePlayer);
+        mRingbackPlayer = new RingbackPlayer(mFactory);
+    }
+
+    @SmallTest
+    @Test
+    public void testPlayerSync() {
+        // make sure InCallTonePlayer try to start playing the tone after RingbackPlayer receives
+        // stop tone request.
+        CountDownLatch latch = new CountDownLatch(1);
+        doReturn(CallState.DIALING).when(mCall).getState();
+        doAnswer(x -> {
+            new Thread(() -> {
+                try {
+                    latch.wait();
+                } catch (InterruptedException e) {
+                    // Ignore
+                }
+            }).start();
+            return true;
+        }).when(mTonePlayer).startTone();
+
+        mRingbackPlayer.startRingbackForCall(mCall);
+        mRingbackPlayer.stopRingbackForCall(mCall);
+        assertFalse(mRingbackPlayer.isRingbackPlaying());
+        latch.countDown();
+    }
+}