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I have a MacBook Pro and last time I observed a strange behavior. When the fridge is turning on (to start cooling down again) I get a loud noise through the headphone jack on the external sound system. This also happens if the fridge is itself turning off (but not so loud as before).
I never experienced such behavior before on any of my devices (including PC). But I noticed this noise doesn't appear if I listen to music on the internal speakers of the laptop.
Has somebody an idea why this is happening and what I can do against this?
1Does this only happen when you've got the notebook plugged into AC, or does it also do this when running (only) off battery? What exactly is your "External sound system"? Does it have an amplifier that's powered by plugging it into the wall? – Ƭᴇcʜιᴇ007 – 2016-01-22T20:44:53.693
1It also happens if I'm running on battery. I'm using a Logitech Z2300 and it has an own amplifier powered by plugging it into the wall. It is probably the same circuit the fridge is running on. – testing – 2016-01-22T20:46:45.563
1Yeah, that's generally a bad idea. High-powered devices really should be on a different circuit than computing equipment. Even with low-pass filters, the power adapters of most computing equipment let through dirty voltage in such cases which can drastically reduce their life. – Mekki MacAulay – 2016-01-22T20:48:50.190
1It's most likely the amplifier in your Logitech speakers amplifying the power fluctuations in the AC line when the fridge turns on and off. Plug it into a different AC circuit and see if it behaves the same way. – Ƭᴇcʜιᴇ007 – 2016-01-22T20:49:44.677
What do you mean with drastically reduce their life? The life from the computing equipment? – testing – 2016-01-22T20:53:17.140
Yes. Dirty power from having high-powered devices like fridges, microwaves, etc. on the same circuit as computer equipment will slowly damage the circuits in the computing equipment (with much variance depending on the actual design--This is where "cheap" stuff tends to fail much faster than stuff built with higher-end circuitry). – Mekki MacAulay – 2016-01-22T20:56:18.450
As a specific example, a client of mine went through /4/ routers in 2 months because the router was on the same circuit as the microwave + fridge. All the routers were electrically fried. Switching circuits fixed it. – Mekki MacAulay – 2016-01-22T20:57:14.877
@Ƭᴇcʜιᴇ007: Now I tested it with the same settings (same circuit, same external speaker) but with another (old) laptop. Here it works without problems. That is weird ... Running the Logitech alone also doesn't produce the noise. – testing – 2016-01-22T22:19:41.577