My (powered) noise cancellation headphones (Sharper Image, "Quiet Place" model), have worked very well over the years until recently. Over the last six months, they have developed a deep sounding, "hum" noise when I plug them into a headphone jack and switch them on.

Mysteriously, the noise goes away when I touch something metal and returns again when I remove my hand from the metal object I was touching.

If I remove the plug from a headphone jack, but leave the power switch on, the noise disappears.

If I switch the headphone power off, but leave them plugged in, there is no noise then, either.

I was recently watching a movie on my laptop when it was time to plug in the laptop's power supply, again. As soon as I did, the "humming" noise disappeared.

Can anyone enlighten me with what has developed, that suddenly caused
this problem, and what I can do about it? It took me a long time to find some headphones that I liked, so, I would rather correct the problem rather than replace them with a new pair of headphones.

 

It sounds to me like AC hum is getting into your headphone circuit because the equipment you are plugging your headphones into is not grounded properly. Make sure your stereo or whatever you are plugging your headphones into is plugged into a properly grounded outlet. Have you changed the way your equipment is plugged into the wall recently?

 

A likely culprit is the connection of the wires to the headphone plug...or at the headphone end of the wire. Check for worn wires and loose connections. If the plug is "molded" so you can't get it apart, you can probably buy a new end and solder the wires onto it.

 

I would look for something that may have changed with the electronics around you. Many consumer electronics come with a non-polarized two-prong AC plug. Sometimes reversing the plug may fix the problem.

I had one client whose stereo would work fine during the day but hummed at night. Of course, because at night he turned the room lights on. The lights were powered by a dimmer switch and that was the source of the electrical noise.