A noise no one else can hear

My dad has been hearing a noise, almost like a very low frequency throbbing noise at night, and it keeps him awake at night and causes him not to sleep. The issue is, is that no one else can hear this noise at all, and we cant tell if he is hearing something, or has something like EHS (exploding head syndrome). He is blaming it on the factories up the road, which are a good 2km away, and it just seems very unlikely that it is them making the noise. So i was wondering if their are any sort of health related issues that can cause things like this while falling asleep, as we don't think its EHS since that is supposed to be a short loud band, but this noise is long and lasts hours, supposedly. Any help??

He does work quite a stressful job, which i know for a fact has caused him to become quite anxious in the past. I did think of that at the start but he says he only hears it in the house, no where else, and usually at night, sometimes in the day, but rarely. I'm basically trying to find a reason to convince him to go and see the GP about it, as it is stressing the whole family out.

I only hear my tinnitus at night in the house ☺️ it’s because it’s dark, it’s night time, your senses are heightened and you’re more likely to worry. I’m going to the doctors about mine tomorrow hopefully - I think it’s been brought on by stress and anxiety caused by University!

Thank you for telling me this, he may actually listen if i have a valid reason for him to see the GP