airtren, "Being disruptive once, or twice, to gain attention is perhaps enough."
Me, "Perhaps a two day old pizza across the face is needed in some cases where there is a persistent lack of attention."
You need to be persistent until a randomly chosen acknowledgement is performed. Then you know you have their attention, however briefly.
The object is not to avoid distraction. Sometimes one must distract the over focused attention of people ignoring warnings.