A judge said a thug could have killed his neighbour in a vicious hammer attack following a row over loud music.
Joshua Walker attacked his victim with a hammer after he complained that loud music was disturbing his sick child.
The neighbour needed hospital treatment to put staples in three cuts in his head caused by Walker, 21, with a claw hammer.
Jamie Robinson, 32, had told him that his nine-year-old son had suffered a seizure in their flat next door in Hartlepool which was being bombarded with loud music.
Prosecutor Emma Atkinson told Teesside Crown Court that he texted Walker at 9.15pm on June 12 appealing for him to turn down the racket.
But Walker texted back: "Knock on the door and say something."
Eventually he went next door where he was confronted by Walker. The men grappled and Walker was armed with a hammer.
Mr Robinson said that he was struck repeatedly on the head with the hammer and he had three lacerations, one of them deep.
He tried to escape into the street and Walker shouted after him: "You're a grass and I'm going to have you."
Miss Atkinson said Mr Robinson reported that it had affected his mental health and he was no longer confident leaving home. He said that his son was having nightmares as a result of seeing his father covered in blood.
Walker was interviewed and he made no reply. The hammer and a baseball bat which was wielded by a teenage girl in the incident were not recovered.
A 17-year-old girl who cannot be identified for legal reasons was later given a youth rehabilitation order after she admitted an affray.
Stephen Constantine, defending Walker who appeared over a videolink from Holme House Prison, said that Mr Robinson, who was a big man, seemed angry when he appeared at his door and Walker picked up the hammer with the intention of assaulting him first.
Mr Constantine said: "He accepts that he went over the top, he was using the hammer to effect some DIY repairs.
"He has lost his accommodation and he accepts that he will have to start afresh when he is released."
The judge told Walker that an immediate prison sentence was inevitable for the attack.
Judge Tony Briggs said: "A possible fatal injury could have been caused but happily on that occasion this did not happen."
Walker, of Borrowdale Street, Hartlepool, was jailed for 21 months after he pleaded guilty to inflicting grievous bodily harm and possessing an offensive weapon.