Turn it OFF!!
It never ceases to amaze me how inconsiderate some people can be.
I'm about halfway through the run of the play No Time For Sergeants at the Hale Center Theater in Orem. Before every performance, the stage manager announces that people should stay in their seats during the performance and that people should turn off any cellular phones, PDA's, and other noisemaking/glowing devices.
There are REASONS behind those announcements. The Hale is a theater in the round. All of the entrances and exits for patrons are also entrances and exits for actors. Thus, someone getting up to go to the bathroom during the middle of a performance may find themselves getting stepped on or otherwise injured by actors that have to make hasty entrances and exits.
But leaving a cellular phone on is very VERY inconsiderate. Even when it only vibrates, it still makes an annoying noise and can possibly interfere with the sound system in the theater. People pay around $15 per ticket to see the play, and when a ringing (or vibrating) cellular phone interrupts the performace, it shows that someone thinks that they're more important than anyone else in the theater. If you're a doctor and you're on call, find another night to attend the theater. People used to go to the theater before there were cellular phones.
On Broadway, the chirping and beeping of cellular phones has become such a nuisance that more than four years ago, the New York City Council passed an ordinance that makes it illegal to use a mobile telephone in a place where a public performance (live or film) or a public lecture is taking place. Unfortunately, it's notoriously hard to enforce such a law, and the pitiful fine of $50 is likely much less than the price of the ticket to the performance the cellular phone user is interrupting.
In France, they have taken it a step further by passing a law that allows active jamming of cellular phone signals in theaters, cinemas, and concert halls. The only proviso is that they have to allow emergency calls through. They're currently working on perfecting the jamming technology to make this a reality.
FCC regulations in the United States make any such jamming device illegal, though there are stories of producers smuggling jamming devices into theaters. Passive jamming (putting metal plates in the walls, for example) is NOT illegal, but because so many theaters on Broadway are landmarks, architectural changes are difficult, if not impossible. New paints and wallpapers exist that can at least partially block cellular signals and are a viable alternative for broadway houses.
But for now, the best we can do is ask people to turn their noisemaking devices off. The plea will be ignored by those who are so self-important that they think they are the exception to every rule. Hopefully, they'll listen closer when "Sergeant King" yells at them, telling them to turn that noisemaker off before he rips their arms off and beats them senseless with them.
It's inconsiderate, not only to other theater patrons, but even more so to the actors on stage who are trying to create an alternate reality through which their audience can temporarily escape their cares and spend an evening laughing and being entertained. The harsh ring of a cellular phone can cause this alternate reality to dissolve, bringing back all of the cares and woes that other audience members might be trying to escape.
So please, when you go to the theatre, TURN YOUR CELL PHONE OFF!