Interference near/in malls?
Dec 23, 2005 at 10:24 PM Thread Starter Post #1 of 8

Firestarter

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I've been walking round town with my trusty HD 25-1's for quite a while now, and I find them ideal to block out nasty music (christmas tunes anyone?) and yelling babies at malls. However, in a few cases, entering a shop caused a rather loud tone to be emitted from my headphones, somewhere between 4khz and 6khz (very rough guess). It varies greatly in loudness (but not pitch) when I move my head around, and it's equally strong on both sides (doesn't move from side to side)

I've had this experience more than once in one particular shop, where it was bad enough for me to take my 'phones off. Has any of you experienced this before? Does anybody have the slightest idea what could've caused it?

My only guesses would be the blowers/heaters at the entrance, or the anti-theft systems. It seems to be worse right at the entrance...
 
Dec 23, 2005 at 11:49 PM Post #2 of 8

markot86

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I experience this too every time I walk into the library; I've pinpointed it to those security things that they have near the doors causing it, however I don't know why they do so.
 
Dec 24, 2005 at 12:45 AM Post #3 of 8

firefox360

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Some of those theft detecting towers use electromagnetic waves to detect a magnetized tag in different items (one of the reason they run items on the counter over a sqaure plastic board). That might be causing the cones in your headphones to viberate at the same pulse as the towers are sending out causing an unpleasant noise.

This is especially noticable in libary's as magnetic theft-prevention tags are reusable and are more cost effect, which really does suit libary usage. Once people return books they run the tag over a machine that magnetizes it and basically arm the tag.

Hopefully you can understand me, kind of tired since I had a Christmas party this afternoon and have been running around non-stop since then.
tongue.gif
 
Dec 24, 2005 at 3:57 PM Post #5 of 8

mrarroyo

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Quote:

Originally Posted by markot86
that makes perfect sense, thanks =) would this be hurting the headphones in anyway? the first time it happened i thought i had tinnitus, scared the crap out of me =P


Actually you should be more concerned about your ears. If the noise that is emitted is loud and an specific frequency it could damage your hearing.
 
Dec 24, 2005 at 4:20 PM Post #6 of 8

stevesurf

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Since the strong fields of today's active Electronic Article Surveillance System Sensor/Transmitters are meant to induce a microcurrent in the passive tags found in books, etc., sensitive audio equipment could concievably be damaged if left within the field (between the "hoops" or "pods") for an exteneded period of time. I will also check with my EAS buddies to find out further info.
 
Dec 24, 2005 at 4:38 PM Post #7 of 8

acidboy84

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But it doesn't seem to have an effect on IEMs. I listen to my Shure E4c a lot and have never encounter such problems. Is it due to the size of the drivers/magnets?
 

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