Residents say the noise has got louder in recent months
Equipment to trace the origins of a noise which has been disturbing the residents of a village has been set up.
The low frequency hum has become such a nuisance for residents in Minffordd, Gwynedd they claim it is disturbing their sleep.
A Gwynedd council spokesman confirmed equipment had been placed in the area to try and record the noise.
Neighbours Nan Griffiths and Rhian Williams first started hearing the low humming sound two years ago.
It has described as being similar to a generator or diesel engine and residents say it has worsened over the last few months.
"The situation is made worse because there is no way to predict when it will start," said Ms Griffiths.
"It's not there all the time, and then it'll wake you up at three o'clock in the morning."
Ms Griffiths said not everyone can hear the noise either, which made her first suspect that she was suffering from tinnitus.
"But then I realised that I wasn't when I found out that two of my neighbours had also been hearing it," she said.
"It's not that I'm not used to noise as I live near a quarry, and I am used to a lot of noise, it's just this one is driving me mad," she added.
Ms Griffiths said she had been given equipment by Gwynedd Council to record the noise.
Neighbour Rhian Williams said she had also suffered.
"I was able to mostly ignore it until about a month ago when it got much louder and I had to turn the radio right up to drown it out," she said.
A Gwynedd Council spokesman confirmed a complaint had been received from a resident about low frequency noise at Minffordd.
"Officers from the council's public protection unit have visited the site to monitor the sound level in the area, and the investigation is continuing," he added.