West Haven officials said Thursday an acoustic study has solved the mystery of what has been causing a strange humming noise throughout the city.

Earlier this year, city officials said that despite conducting hundreds of tests, they could not figure out the source of the noise.

Acoustic Technology LLC was hired and took readings at more than 10 locations in neighborhoods near Heffernan Drive.

City officials say the tests found a tone that "reduces the allowable noise levels by 5 decibels to 46 decibels at night for noise traveling from an industrial zone into a residential zone." Officials say the tone came from the Glanbia facility on Heffernan Drive.

Acoustics engineers hired by the company determined that "roof-mounted silencers, or mufflers, that were replaced in 2024 are insufficient for the particular tone generated by the equipment."

Glanbia has begun to install custom silencers, which will be completed by late September. Until then, the company has installed temporary muffler blankets and U-bends to mitigate sound levels.

During the first two weeks of the temporary solution, the city monitored the noise levels and found that decibel readings were all within allowable range.