android的Notification提醒的问题

我使用自定义的通知，在其中的defaults设置成Notification.DEFAULT_SOUND，详细代码在下面。在执行 的时候能听见声音，但是通知栏没有这个通知，为什么呢？
public void showNotification(){
Notification no=new Notification();
no.flags=Notification.FLAG_AUTO_CANCEL;
no.defaults = Notification.DEFAULT_SOUND;

RemoteViews remoteviews=new RemoteViews(this.getPackageName(), R.layout.notifition_layout);
remoteviews.setImageViewResource(R.id.image, R.drawable.img01);
remoteviews.setTextViewText(R.id.text1, "这是通知DEMO！！！");
remoteviews.setTextViewText(R.id.text2, getnow());
no.contentView=remoteviews;
Intent i=new Intent(MainActivity.this, MainActivity.class);
PendingIntent p=PendingIntent.getActivity(MainActivity.this, 0, i, PendingIntent.FLAG_CANCEL_CURRENT);
no.contentIntent=p;
NotificationManager manager=(NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
manager.notify(0, no);
}