On the second bang, he got up to check on Ihaka and found him with some bleeding around his mouth. He also "looked a little bit dazed and confused".
He got him up, put Bonjela teething gel on his mouth and they sat in the lounge by the fire in the dark to make sure he was all right, Taylor told the jury.
After about 10 minutes, Taylor says he sat up too quick, got dizzy and "then I dropped him".
Taylor has also today explained his version of events on the night that Ihaka died.
He says that while he was out getting a tattoo - the period of time he says Stokes caused the boy's fatal injuries - Stokes had texted to say she had had to "walk away" from Ihaka.
When he got home at about 6.30-7pm that night, he says Stokes was "cold, standoffish".
He says he heard Ihaka grizzling in his bedroom. He says he popped his head in the door and assumed he was nearly asleep.
After making himself dinner, and watching TV, Taylor says he checked on Ihaka as he went to bed shortly after 8.30pm.
As he approached his cot, Ihaka was lying on his back, eyes partially open, staring up at the roof, Taylor told the court.
Earlier, co-defence counsel and brother Simon Shamy told the jury that the nub of the defence case was that Stokes, not Taylor, caused the 59 injuries that killed Ihaka.
"The Crown case unravels because there is no proof that it was Troy Taylor rather than Mikala Stokes who delivered these injuries," Shamy said.
Taylor was earlier asked about his relationship to Ihaka. He replied: "I don't care what anyone thinks - he is my son."
"I loved them and considered them to be my children."
Taylor also told how he'd planned to adopt Ihaka and Stokes' second child as his own, and that he'd also given Stokes a "commitment ring" to show that one day he would marry her.
Asked about his relationship with Stokes, he became emotional: "She was my best friend. I loved her."
Both the Crown and the defence agree there were no intruders on that fateful night and that the boy's 59 injuries, including broken bones, were not accidental.
The Crown says that Taylor was suffering from sleep deprivation, headaches, and irritability caused by multiple concussions around the time Ihaka was developing an ear infection, when he allegedly caused the fatal injuries.
Stokes, who was 36 weeks' pregnant with her second child at the time of Ihaka's death, repeatedly denied the accusations when she gave evidence last week.
Taylor also denies assaulting the child on July 2, 2015 - the day before the alleged murder.
The trial, before Justice Cameron Mander, continues with Taylor's evidence.