Your descriptions of a 'diesel engine starting' are different than the description in the wiki article of a diesel engine running. A running diesel engine would make a droning hum, while a starting one would click or tick and thump faster and faster into a hum.
That start-up noise is very similar to the sound of a grouse, a common bird in rural areas. A friend and I were hiking for a few days a few years ago, and we felt completely isolated and hadn't heard human noise for days... except that someone kept starting an engine a few hundred yards away! We knew it must not be people, but were baffled.
When we finally got back we asked his family members if they knew the source of those noises, and they showed us a youtube clip about grouse. Surprisingly noisy little things. I would seek a video for you, but I am on a restrictive telephone.
Could it be a grouse?
Your descriptions of a 'diesel engine starting' are different than the description in the wiki article of a diesel engine running. A running diesel engine would make a droning hum, while a starting one would click or tick and thump faster and faster into a hum.
That start-up noise is very similar to the sound of a grouse, a common bird in rural areas. A friend and I were hiking for a few days a few years ago, and we felt completely isolated and hadn't heard human noise for days... except that someone kept starting an engine a few hundred yards away! We knew it must not be people, but were baffled.
When we finally got back we asked his family members if they knew the source of those noises, and they showed us a youtube clip about grouse. Surprisingly noisy little things. I would seek a video for you, but I am on a restrictive telephone.