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Author Topic: Why do my speakers hum when I touch the connector jack?  (Read 7914 times)

Leisha

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Leisha asked the Naked Scientists:
   
Why do my speakers hum when I press the speaker jack against my skin or
hold it in my fingers? Can it hear the electricity my body gives off?

Thanks, love the show,
Leisha

What do you think?


 

Offline Vern

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Why do my speakers hum when I touch the connector jack?
« Reply #1 on: 03/03/2009 11:18:58 »
The electrical wiring in your house radiates a signal at the house frequency usually 60 hz in the US and 50 hz in UK. Your body acts as an antenna for this house frequency. When you touch your speaker connector you couple the wiring signal to your speaker - amplifiers.
 

Offline yor_on

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Why do my speakers hum when I touch the connector jack?
« Reply #2 on: 03/03/2009 19:07:50 »
Didn't know that one Vern, I've always assumed it was static electricity,
 

Offline Vern

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Why do my speakers hum when I touch the connector jack?
« Reply #3 on: 03/03/2009 19:32:14 »
Didn't know that one Vern, I've always assumed it was static electricity,
I guess you could call it static. Good old power company static :) There's also atmospheric static riding on top of the 60 cycle hum (or 50 cycle hum).
« Last Edit: 03/03/2009 19:35:02 by Vern »
 

Offline LeeE

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Why do my speakers hum when I touch the connector jack?
« Reply #4 on: 03/03/2009 20:11:32 »
I don't think that it can be the 'speaker jack' that's being touched to produce the hum; the speakers deal with relatively high amounts of power when compared with what could be induced in the human body.
 

lyner

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Why do my speakers hum when I touch the connector jack?
« Reply #5 on: 03/03/2009 23:36:00 »
I think his speakers must have an amplifier inside them.
 

Offline Vern

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Why do my speakers hum when I touch the connector jack?
« Reply #6 on: 04/03/2009 06:13:53 »
I think his speakers must have an amplifier inside them.
Yes; I've never heard of a bare speaker with no amplifier being sensitive to the local power grid hum. However, if you live under the transmission line, lots of things become lively :)
 

Offline syhprum

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Why do my speakers hum when I touch the connector jack?
« Reply #7 on: 04/03/2009 08:28:07 »
To some extent things work the other way around, although nominally grounded the casing and outer casing of the amplifier cable may well have a small mains frequency potential upon it.
When you hold the inner conductor you provide a ground connection and this potential appears as an input to the amplifier although this is only apparent if an amplifier is included in the speakers, it is possible to notice it on sensitive earphones without an amplifier.
« Last Edit: 04/03/2009 20:19:47 by syhprum »
 

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Why do my speakers hum when I touch the connector jack?
« Reply #7 on: 04/03/2009 08:28:07 »

 

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