Smith admitted that he is frightened of the aliens, who have the power to erase themselves from the memories of anyone who sees them.
"They are the best monsters since the Weeping Angels - they are certainly some of the scariest. What is wonderful is that they toy with your psyche. They mess with what you know and don't know and what you can and can't remember - they can influence your mind," Smith said in an interview quoted by PA.
"They look horrendous and are really mean. So if you're under the age of 10, a good sofa to hide behind is essential. That's what Doctor Who should be about: 'I don't want to watch this, but also I do'!"
The Silence first appeared on screen in the two-part series six opener 'The Impossible Astronaut'/'Day of the Moon' and returned for another showdown with The Doctor and his companions in the finale 'The Wedding of River Song'.
Smith's co-star Arthur Darvill also recently singled out The Silence as his favourite Doctor Who monsters, describing them as a "brilliant creation".
Last week, Smith denied rumours that he plans to leave Doctor Who after filming the sci-fi show's upcoming seventh series.
Doctor Who returns for a holiday special on Christmas Day on BBC One in the UK and will likely air on the same day in the US on BBC America.
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Watch Digital Spy become a monster at the Doctor Who Experience below: