JOHANNESBURG: Match referee Roshan Mahanama on Saturday defended television umpire Daryl Harper after a controversial decision during the fourth and final Test between South Africa and England.

Mahanama denied telling England coach Andy Flower that Harper had failed to adjust the volume of an audio feed from the stump microphone before upholding a decision by on-field umpire Tony Hill to turn down an appeal for a catch behind the wicket against South African captain Graeme Smith.

In a statement issued through the International Cricket Council in Dubai, Mahanama said Harper had followed the correct protocol.

He said the volume on the third umpire's feed was set by a head engineer of the host broadcaster, the South African Broadcasting Corporation, and an ICC technical adviser.

"If the audio level had been increased above its optimum level, distortion on the audio feed would have occurred and the feed might not have given a clear indication of the true sound," he said.

"At no stage (had) I indicated to the England team management that the third umpire had forgotten to adjust the volume of the speakers. I had actually briefed the England team management of the protocols that were followed during this review.

"It should be kept in mind that the TV umpires sometimes receive feeds which are at a different level to what others are receiving for the simple fact that various broadcasters at times use different technologies while televising a match and the Johannesburg Test is a case in point."

This tallies with what Flower told journalists on Friday evening when he said he had been informed by Mahanama in a first meeting with the match referee following the incident that Harper did not receive the same feed as South African pay channel SuperSport and England's Sky television.

Viewers of SuperSport and Sky clearly heard a noise as the ball passed the edge of Smith's bat but there was apparently no obvious noise on the SABC broadcast, which it appears is the same feed received by the television umpire.

But Flower then said: "On subsequent investigation we found that wasn't correct. I went back and this time he said that Daryl Harper hadn't turned up the volume on his mic. We have heard the nick but the third umpire hasn't."

Flower said he was "very disappointed" with the decision and planned to make an official complaint.

According to Mahanama, "the third umpire, when reviewing the decision, used a range of technologies that were made available to him by the host broadcaster, including the slow-motion replays, amplified stump microphone sound (at normal speed and slow motion), approved ball- tracking technology and pitch mat generated by the ball-tracking technology".

"During the review, the TV umpire followed the correct protocol and as he did not hear any noise to indicate the ball hitting the bat, he recommended Mr Hill to uphold his earlier decision. It must be noted that umpire's decision is final.

"In the end, it must be remembered that there needs to be conclusive evidence to over-turn the decision of the on-field umpire as the Decision Review System has been designed to eliminate the obvious umpiring errors."