James McCann, 80, from Norfolk, is accused of violent and sexual assaults on 26 boys aged between eight and 12.
He allegedly abused the boys at St Francis children's home in Shefford, Bedfordshire, in the 1960s and 1970s.
An Old Bailey judge has ruled he is not fit to stand trial and the jury must decide the facts alone.
The home, which was run by the Roman Catholic diocese of Northampton, was closed down in 1974 and the alleged victims are now aged in their 50s and 60s.
Nineteen of them claim violent assault, three allege both violent and sexual abuse, while four say they were exclusively indecently assaulted.
Opening the case against Mr McCann, who is accused of 52 charges, John Price QC said that during the carer's nine years at the home the violence included what was known to the boys as The Clappers.
"Allegedly deployed by McCann on countless occasions, according to the recollections of many of the former child residents, it was a strikingly similar method of what can only be described as a sadistic violent assault," Mr Price said.
"Mr McCann would routinely and seemingly at his whim assault children by clapping the flat of his hands simultaneously over each of their ears."
Mr Price called it a "cruel act" which caused the child "excruciating pain" and the alleged victims also recall nausea, dizziness, disorientation, an inability to stay on their feet, a temporary loss of hearing and ringing in the ears.
When he was interviewed by police about the allegations in 2013 and 2015, Mr McCann, of Swaffham, denied they took place.
The trial continues.
A "cruel and sadistic" carer molested boys at a Catholic children's home and terrorised them with a punishment known as The Clappers, a court has heard.