Video on bootstrap modal popup continues playing audio after closing

I have a very basic you tube video playing on a bootstrap modal popup window. When I press close, the video itself closes but the audio continues to play. Any suggestions would be very helpful. Thanks!!

                                          <div class="modal fade" id="tvDebutPlay" tabindex="-1" role="dialog" aria-labelledby="videoModal" aria-hidden="true">
                                          <div class="modal-dialog2">
                                              <div class="modal-content2">
                                                  <div class="modal-body2">
                                                      <button type="button" class="btn btn-default st-closeBtn" data-dismiss="modal">X</button>
                                                      <div>
                                                          <iframe width="100%" height="480" src=""></iframe>
                                                      </div>
                                                  </div>
                                              </div>
                                          </div>