The days of dressing up for the theatre and enjoying an undisturbed night of entertainment are over, according to a new report.
A rise in younger audiences has led to a large number of theatregoers checking their mobiles, using social media and whispering in the stalls.
Theatregoers between the ages of 25 and 34 are those most likely to check their phones during a performance.
They were also twice as likely as the average theatregoer to think looking at the odd text was acceptable.
Four per cent of theatregoers said they had used Facebook or Twitter during a performance, despite 91 per cent thinking it was unacceptable to do so.
Eight out of ten respondents said they thought whispering during the performance was unacceptable, although 13 per cent admitted they had done it.
Just over half of theatregoers think it is acceptable to wear casual dress to see a play, with the number rising to 72 per cent among 16-19 year olds.
The report by Ticketmaster found 16-19 year olds were more likely to attend the theatre than any other age group, followed by those aged 20-24 and 25-34.
Contrary to popular opinion, the likelihood of attending the theatre decreases by age but starts picking up again for those aged 55 and over.
The increase in younger audiences has been helped by a number of ticket discount schemes, including £12 Travelex tickets at the National Theatre and concessionary tickets for the under-25s at the Old Vic, Royal Court and English National Opera (ENO).
The ENO last year introduced the "Opera Undressed" series, inviting audiences to wear jeans to selected shows.
Alistair Smith, deputy editor of The Stage, said the drive for greater theatre inclusivity has led to "the unintended consequences of people not knowing the rules".
He said: "For quite a long time, probably at least a decade, it's been gradually getting less formal. Instead of a narrow demographic, you are getting people from all walks of life, which is undoubtedly a good thing. But maybe it brought with it the unintended consequences of people not knowing the old rules."