The young team lost 4-1 at home to Brighton and Hove Albion this week, the latest poor home defeat they have suffered.
In the past few weeks they have also lost 4-1 at home to West Ham, 3-0 to Fulham, and 2-1 to Stoke.
Beardsley told the club's official website that the players are daunted by their surroundings.
He said: "It's really disappointing. I said to their coach before the game about how we struggle to play at home. I don't know what it is - if it's the stadium, the pressure of being at home, I don't know what it is - but we haven't really played really well at this stadium in the last two years.
"I don't know if it's a big lift for the opposition, which in some ways it maybe has been for the first team games. Brighton won fair and square. We lost our shape, lost our enthusiasm if you like, and we could've lost by more.
"They shouldn't be overawed here in the sense that they've played here a lot now. Having been to the Emirates on Friday and the Liberty last week, it should be something that they get used to, and have to get used to."
The problem is that Newcastle's under-21 team have been just as poor away from home too, losing 3-1 at Arsenal and 5-3 at Swansea City in the last week.