Research by London Underground shows that a breathy female voice is the most popular choice for announcements on Tube trains.

The company is now planning to replace some of its more mechanical announcers with the warmer tones of a Marilyn soundalike.

A calmer, friendlier voice might reduce tensions on the often packed rush-hour trains.

London's Tube carries more than two million people a day

''We have a variety of announcements on a lot of trains and people definitely respond to some voices better than others," said a spokeswoman.

"We have done some market research and the one that most people preferred was a slightly breathy voice that sounded a bit like Marilyn Monroe. People said she sounded very pleasant and helpful.

"The comment that sums it up best is that she sounded as if she was smiling as she spoke to you."

Tube announcements tell passengers which station they are approaching, advise of problems with the service and ask them to squeeze together if the carriages are getting full.

Digitised voice 'irritating'

The voice that does this on many trains at the moment is nicknamed Sonia by some Tube workers, because "she gets Sonia nerves".

"On some lines, there is a digitised voice which can be irritating if you have to listen to it a lot," said the spokeswoman. "We would rather give people what they actually want."

The research involved a variety of voices in tones ranging from "newsreader" to "schoolmistress".

But the favourite was a softer, more breathy voice, like when Marilyn Monroe famously sang Happy Birthday to President Kennedy in 1961.

The search is now on for the right voice - London Underground says "Marilyn" could be asking passengers to mind the doors in a few months.