Nicole Kidman loves the sound of Keith Urban's voice.

The 48-year-old actress, who is currently starring in the West End production 'Photograph 51' in London, never sends him text messages or emails when they're apart because she prefers talking to him on the phone.

She said: ''My husband and I never text each other. We never do. Once in a blue moon, we'll text. But mainly we say, 'I want to hear your voice.' That's very unusual but we've been together for 10 years. We started like that and we haven't changed it. We don't email each other either. So it's about trying to keep it as intimate and personal as possible.''

But the Oscar winner, who has daughters Sunday, seven, and Faith, four, with Keith, and Isabella, 22, and Connor, 20, with ex-husband Tom Cruise, ''definitely'' relies on text messages to stay in touch with them.

The 'Lion' star said: ''I have four children, so to stay in touch with them it's very important.''

Nicole, who previously revealed Keith frequently writes her love letters, is very grateful to the country music singer, 47, for always making an effort to be with her even if it's just for a few hours.

She told the October issue of DuJour magazine: ''I'm lucky that we have such a strong family unit. I have an incredible husband who is so willing to get on planes and fly places, even if it's for a night. I had an opening of the play three nights ago, and he's in the middle of a tour in the States. I said, 'It's too much for you to have to fly all the way back, don't worry,' and he said, 'I'm flying.' ''