The noise - nicknamed the “Beauly Buzz” by residents – comes from the Wester Balblair sub-station near the village.
It was built to feed electricity created from the growing number of renewable energy projects in the area into the National Grid, via the £600million Beauly-Denny power line.
But nearby residents have complained of a low-frequency humming and Highland Council issued a noise abatement notice in February, directing SSE to resolve the continuous sound.
SSE, which initially claimed there was no problem, said it is now working on reducing the noise and spending £2.5 million to do so.
David Gardner, the firm’s transmissions director, said: “It takes time to find solutions because of the complex nature of the problem, but we are taking this very seriously.
“I do not want to be in this position again.
“It is difficult for me to have to try to manage and it is certainly not good for our reputation.”
Earlier this year environmental health officers from Highland Council investigated the complaints and found a “statutory nuisance” did exist.
Failure to comply with the terms of an abatement notice without reasonable excuse may result in prosecution.
Specialist acoustic jackets which are made for sub-station equipment have been ordered and should be fitted around six circular reactors in October.
Large green sound barriers have also been placed around other reactors.
In addition, a defective reactor was returned to the manufacturer in Italy last month for repair.
Residents the noise was first noticed when the expansion of the sub-station at the start of the 137-mile overhead power line was upgraded to 400,000 volts, to carry renewable energy generated in the Highlands and Islands to the south.
The first section between Beauly and Fort Augustus went live last year.
Steve Byford, chairman of Kilmorack Community Council, said he and his neighbours in Broallan, which is around a mile-and-a-half away from the site, are at times woken up during the night.
On one occasion, he measured 43 decibels using a downloaded mobile phone app.
Department for Environment, Food & Rural Affairs (DEFRA) guidelines suggest 30 decibels are an acceptable sound level in a bedroom at night.
He said: “It is very distracting and upsetting. The trouble is with the nice weather you want to open the windows and let in the breeze at night, but the noise has been so loud you are not able to do that.”
He claimed SSE should have been aware of the potential for noise to be heard for miles around.
He added: “If it had shown due diligence and done the noise survey correctly before work began, it would have known the noise impacts of these transformers.
“The evidence is out there. The same transformers are fully enclosed in plants elsewhere.”
Highland Council officials said the noise had become apparent since the commissioning of new equipment installed at the site as part of the Beauly-Denny upgrading works.
Councillor Graham Phillips, chair of the council’s transport and environment committee, said: “We acknowledge the steps SSE have taken to investigate the source of the noise and their stated commitment to resolving the issue.”