The former child star is promoting his new film, What If, in which he plays a medical student who forms a strong bond with a girl who is already in a relationship with another man.
The 25-year-old British actor has been plugging the rom-com since it premiered at the Toronto International Film Festival last autumn and says he starts to hate his own catchphrases.
Speaking on the red carpet at the first annual IvyConnect's Innovator Film Award in Los Angeles, where he introduced a screening of his new film, Radcliffe said: "When the film is as good as this I don't get bored talking about it but I get bored of the sound of my own voice.
"Somebody asked me what the most annoying sound in the world is and the answer was me saying the words 'you know'. It's my pause phrase that I say all the time and it gets boring."
Radcliffe stars opposite Zoe Kazan in the comedy, which features a scene where the pair swim naked in a rather murky Lake Ontario.
Asked if he was worried about the effects of swimming in that kind of water, he joked: "We went in the lake then told loads of Canadians that we went skinny-dipping in Lake Ontario, and they said they wouldn't have done that. But we are here two years later... It's our children's children that will spout radioactive deformities as a result, so we are fine."
The movie is released in the UK on August 20 and Radcliffe said he can't wait for audiences to see it.
"I think it's a very unusual film because it gives a gift to an audience of making people happy, because to make someone happy with a movie without resorting to sentimental tricks or [being a] schmaltzy, cheesy movie is a hard thing to do and I think we do it really well.
"I think it's a feel-good film that is a guilt-free pleasure because it makes you happy and makes you laugh and hopefully stays with you at the end. It should be moving if we have all done our jobs."
Radcliffe has embraced a wide variety of roles since hanging up his wand at the end of the Harry Potter franchise and he said the differences are what keep him coming back.
"I think it's the differences that make me excited; having played one part for so long it builds up a desire to try as many things as you can. It's also about finding out what I'm good at, what I like doing, it's all of that. There's no theme or pattern, when a pattern emerges I will try to shake it off immediately," he said.