Severe short term audio distortion when watching Netflix

It's the fact that the duration of the distortion is always 3-4 seconds only  - not longer , not shorter and only once per night - just at different times during the 3 hour timeframe

If it was interference from outside - why always the same length?, and why only once?

The 3 second of distortion on it's own is no big deal from my perspective - just don't want it to be slowly frying my speakers - even though I recognize it straight away and immediately turn the volume down - it may happen when I'm out of the room

Do you live in a single family home or multi-unit building?  Does someone in your residence or a neighbor return home during that time window and switch on some device, like an air conditioner or something that might be drawing a heavy load for a couple minutes and possibly interfering with your power?

Yes I live in a 5 unit group - 3 units in my block and a separate block of 2 units

Entirely possible that my neighbours are coming in and out and switching on AC, devices etc- But this has only started happening 12 nights ago - nothing has changed in my system and neighbours are the same - and I've been home for the last 2 months  and haven't seen any work installing new AC etc 

It's a burst of data flowing inside the computer that's causing the interference. Or maybe it's a bad bit if memory and the time >s irrelevant or only relevant to the extent that is the time you typically use it for this purpose. 

Thanks Gregdude - But again, the computer is running and I'm watching something online - either you tube or Netflix most of the day and night ( I'm retired and lazy !)

Why did it only start 12 nights ago and how do I identify and isolate that burst of Data?