Gareth Southgate's side are in deep danger at the bottom end of the Premier League.
And boos rang out at the Riverside after Saturday's 1-1 draw with Spurs.
O'Neil said: "The fans are getting frustrated but it is a hard time for everyone.
"Booing doesn't help anyone. We need the crowd behind us more than ever.
"The fans pay their money and are allowed their opinion - but it's not nice to hear."