I was getting the warning:

new NativeEventEmitter() was called with a non-null argument without the required removeListeners method.

I was using React Native Sound and to fix the warning I add the below lines of code to this file in the react-native-sound module: react-native-sound/android/src/main/java/com/zmxv/RNSound/RNSoundModule.java

// Explicitly implement addListener
  @ReactMethod
  public void addListener(String eventName) {
    // Required for RN built-in Event Emitter Calls.
  }

  // Explicitly implement removeListeners
  @ReactMethod
  public void removeListeners(Integer count) {
    // Required for RN built-in Event Emitter Calls.
  }