Reeva Steenkamp's screams could have hit 120 decibels, a volume comparable to a plane's engine, as she was gunned down by Oscar Pistorius, his murder trial was told.

Acoustics expert Ivan Lin told the court it would have been at the "extreme" end of the human noise spectrum.

Prosecutor Gerrie Nel questioned Lin on the noise, which could be crucial in the case because neighbour Michelle Berger claimed she heard a woman screaming on Valentine's Day last year, when Steenkamp, 29, was killed.

However, Pistrorius's lawyer Barry Roux claims it was the runner who made the loud screams because he sounds "like a woman" when scared.

Lin said: "120 means extremely loud, you can almost hear it 100 metres away. It is a very slight possibility, but it is possible."

Lin said he was unable to say for certain who made the noise heard by Berger.

"It's not for me to interpret. From a scientific perspective, I still can't say 'were they correct, were they incorrect'," he said.

Pistorius denies murdering Steenkamp and claims he thought she was an intruder in the bathroom of his luxury home, in Pretoria. The prosecution claim he killed her in a rage following an argument.

The trial continues.