Cell Phones off. Pagers, ditto. But what about those whistling hearing aids? “This is a delicate matter. Users of hearing aids at performances have an unfortunate impairment and are still, to their credit, trying to enjoy live music. Moreover, a person wearing a hearing aid often cannot hear the whistling that his device sometimes produces. It is a pesky sound to track down for others in the hall. Those high-pitched sustained tones throw you off. You could be sitting just seats away from a malfunctioning hearing aid and think that the whistling is coming from somewhere up in the balcony.”