Yes I think that's what it is, an external pond pump in a housing. It's difficult to tell from behind the fence, but I think there is a white metallic housing right next to the pond where the pump could be. I've asked him to come over so hopefully we can discuss in more details *fingers crossed*
I'd guess it's air stones run by a diaphragm pump that's causing the hum. I have seen piston pumps that are almost silent - I've also heard piston pumps that are very loud. There's no need for air-stones in a fish pond if the pond has filtration as filtration will move the water around enough. Air stones just produce bubbles - they do not oxygenate the water (your NDN may suggest it does, but it doesn't). A pond pump just pumps water around and should be silent - it's just an impeller spinning round and makes no noise. An air pump just provides bubbles and hums because the diaphragm is vibrating at 50Hz
It's most likely to be an external filter system with integrated pump as a simple pond pump is normal in the pond. My guess is that the pump is causing the filter box to vibrate, and the effect of that can be surprisingly directional. Ask the neighbour to put their hand on the box to see if it is vibrating and go from there.
@Papi Jo I know English isn't your first language (although we'd hardly know that from your posts) but how can you have been on here for so long and not sussed that one out ... NDN = Next Door Neighbour 👍
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
I'd guess it's air stones run by a diaphragm pump that's causing the hum. I have seen piston pumps that are almost silent - I've also heard piston pumps that are very loud. There's no need for air-stones in a fish pond if the pond has filtration as filtration will move the water around enough. Air stones just produce bubbles - they do not oxygenate the water (your NDN may suggest it does, but it doesn't). A pond pump just pumps water around and should be silent - it's just an impeller spinning round and makes no noise. An air pump just provides bubbles and hums because the diaphragm is vibrating at 50Hz
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I have seen piston pumps that are almost silent - I've also heard piston pumps that are very loud.
There's no need for air-stones in a fish pond if the pond has filtration as filtration will move the water around enough. Air stones just produce bubbles - they do not oxygenate the water (your NDN may suggest it does, but it doesn't).
A pond pump just pumps water around and should be silent - it's just an impeller spinning round and makes no noise.
An air pump just provides bubbles and hums because the diaphragm is vibrating at 50Hz
Ps have a listen here to a 50Hz sound and see (or hear) if it matches the sound you hear https://www.youtube.com/watch?v=bslHKEh7oZk
Billericay - Essex
Knowledge is knowing that a tomato is a fruit.
Wisdom is not putting it in a fruit salad.
NDN ? What are they?
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
That sounds like a wise course. Maybe you can go and visit them also - bring cake. Cake resolves most of the world's issues, I find.
Billericay - Essex
Knowledge is knowing that a tomato is a fruit.
Wisdom is not putting it in a fruit salad.