On Easter Sunday in 2008, the phantom noises in Robert De Mong’s head dropped in volume — for about 15 minutes. For the first time in months, he experienced relief, enough at least to remember what silence was like. And then they returned, fierce as ever.

It was six months earlier that the 66-year-old electrical engineer first awoke to a dissonant clamor in his head. There was a howling sound, a fingernails-on-a-chalkboard sound, “brain zaps” that hurt like a headache and a high frequency “tinkle” noise, like musicians hitting triangles in an orchestra.

Many have since disappeared, but two especially stubborn noises remain. One he describes as monkeys banging on symbols. Another resembles frying eggs and the hissing of high voltage power lines. He hears those sounds every moment of every day.

De Mong was diagnosed in 2007 with tinnitus, a condition that causes a phantom ringing, buzzing or roaring in the ears, perceived as external noise.

When the sounds first appeared, they did so as if from a void, he said. No loud noise trauma had preceded the tinnitus, as it does for some sufferers — it was suddenly just there. And the noises haunted him, robbed him of sleep and fueled a deep depression. He lost interest in his favorite hobby: tinkering with his ‘78 Trans Am and his two Corvettes. He stopped going into work.

That month, De Mong visited an ear doctor, who told him he had high frequency hearing loss in both ears. Another doctor at the Stanford Ear,…