The report, published this month, links the "aversive behaviour" of a number of the koalas observed to Bluesfest Byron Bay, where the koalas moved away from their home-range area, "perpendicular to and away from staging areas where music was played", the report showed.

"For koalas to get up and leave their home-ranges is quite significant," author of the report and managing director of Biolink Ecological Consultants, Steve Phillips, said.

"Koalas are very particular about what they eat and where they live so, if they're bombarded by this low noise, it's potentially coming from a bigger koala. They're going to pack up and leave; they fear it," he said.

The report showed three of the radio-collared koalas whose core home-ranges were within 525 metres of the festival arena moved out of these areas.

Three others located further out also showed movement patterns that led away from the festival but stayed within their home-ranges.

Behavioural observations on the last koala showed signs "morbidity", including lethargy during the music event. This koala was found dead after the study but the cause could not conclusively identified.

The report suggests the increased stress from the noise created by the festival that causes the koalas to move about could "compromise immunological processes", leading to increased susceptibility to disease.

"The question the paper asks is, 'At what cost are the koalas moving?' And we don't know what that cost is," Dr Phillips said.

Sean FitzGibbon from the Koala Ecology Group at the University of Queensland said, "It is commonly known stress predisposes animals to disease, but there is not a lot of evidence to say this occurs in koalas."

Dr FitzGibbon, who heads the consultancy team for Bluesfest, said the group had made huge progress treating diseased koalas since the five-year-old data was taken when there were very high levels of disease, causing death in local numbers.

"We've been monitoring them in the four years since [the study was done] at every festival. At each Bluesfest we track the koalas daily to make sure they're comfortable, in a normal area and out of harm's way," he said.

"The conclusions from Mr Phillips' study are not supported by the data we have collected in the four years since."

Dr FitzGibbon also said the koalas' stress responses from the festival were "minor" because three of the koalas tracked in the study didn't move out of normal ranges, showing no "aversive responses" and three that did moved only short distances, returning soon after.

"That's what we hope they would do at a festival site," he said, and some of them "were in the area we would expect to find them. You can't know if they moved because of music."

"I think the main threats to koalas at the site are disease and wild dogs and Bluesfest is making big efforts to mitigate [their] impact," he said.

Bluesfest director Peter Noble said the monitoring of koalas on the Tyagarah Tea Tree Farm property was "best practice".

"What we're doing on my site is hard work. We've invested hundreds of thousands of dollars to create an environment where the koala population can increase," he said, adding that Bluesfest was the only festival to have a koala plan of management approved by the NSW government.

"Our goal is to have disease-free koalas on our site. We take this seriously," he said.

Dr Phillips said ongoing monitoring was important to ensure a healthy koala population and performance indicators needed to be used to measure their progress.

"We all want to arrest decline [in koala numbers]," he said. "If the result [from the paper] is that we learn and improve our managing techniques, that's a good thing."