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Author Topic: Why does this light make such a high pitch noise ?  (Read 16133 times)

Offline neilep

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Greetings wonderful lovely clever peeps. You know..I could hug you all, and perhaps slip in a quick grope too !! :D

errhhmm...




Why does this lamp of fluorescent goodness and illuminating joy give off such a high intense pitch/whine ?..it's faint but ever so noticeable...it really annoys me and when you can hear it...you can't stop hearing it !!!!

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Offline neilep

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Re: Why does this light make such a high pitch noise ?
« Reply #1 on: 06/12/2005 16:50:33 »
Errhhmmm..would it make any fifference if I said it ran off batteries ?...though the light is not dimming could it be an indication that the batteries are losing energy ? I am also losing energy hence the reason I can not be bothered to change the batteries to find out..It takes EIGHT !!...Yes EIGHT !!!..that's a lot of battery-change-time-wastiness !!

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Offline Soul Surfer

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Re: Why does this light make such a high pitch noise ?
« Reply #2 on: 06/12/2005 23:25:51 »
The audio noise is probably the frequency or a harmonic or subharmonic of the DC/AC converter that drives it.

Flourescent tubes have to run off alternating current to balance the wear on their electrodes they also need quite a high voltage to get them going.  If you want to get an alternating current from a battery you have to run some sort of oscilator from  the DC power source and transform its output to the required voltage to run the gas disharge in the tube.  It is more efficient if these run at frequencies higher than the normal 50Hz mains so they often use audio, ultrasonic or even radio frequencies.  The most likely source of the sound is magnetostriction in the coil that forms a major part of the oscillator although the discharge in the tube can also make a noise.

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« Last Edit: 07/12/2005 12:45:19 by Soul Surfer »
 

Offline neilep

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Re: Why does this light make such a high pitch noise ?
« Reply #3 on: 06/12/2005 23:35:54 »
Ian..thank you very much.

That must be why it causes havoc when it's within close proximity of my el cheapo radio. So, presumably there is no way to dampen this high pitch whine ?

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Offline DoctorBeaver

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Re: Why does this light make such a high pitch noise ?
« Reply #4 on: 07/12/2005 00:09:19 »
High-frequency sounds do not travel easily through water. Try sticking the lamp down the bog :D

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Offline ukmicky

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Re: Why does this light make such a high pitch noise ?
« Reply #5 on: 07/12/2005 00:38:58 »
High-frequency sounds do not travel easily through water. Try sticking the lamp down the bog

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I cant believe the good DOC suggested that.

I mean its quite obvious, it would never fit. I would try the bath myself. :)



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« Last Edit: 07/12/2005 00:52:17 by ukmicky »
 

Offline DoctorBeaver

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Re: Why does this light make such a high pitch noise ?
« Reply #6 on: 07/12/2005 01:09:30 »
quote:
I mean its quite obvious, it would never fit


How do you know how big it is?

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Offline ukmicky

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Re: Why does this light make such a high pitch noise ?
« Reply #7 on: 07/12/2005 01:55:00 »
NEIL how big is it.

Going by the mobil phone in the back ground i would say its between 18 inchs to a foot long.

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Offline DoctorBeaver

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Re: Why does this light make such a high pitch noise ?
« Reply #8 on: 07/12/2005 01:59:07 »
Gravitational lensing
 

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Re: Why does this light make such a high pitch noise ?
« Reply #9 on: 07/12/2005 12:39:13 »
Hi Neilep,
you could avoid that humming noise and avoid electricity bills by moving your fluorescent tube light close to high-voltage transmission lines,(see link):-

http://www.pureenergysystems.com/news/exclusive/2004/pylon_ambience/

Long fluorescent tubes are particular offenders because the voltage required, and consequently transformer size, is proportional to the square of the tube length, (transformers are unintentional loudspeakers).
« Last Edit: 07/12/2005 12:47:24 by ROBERT »
 

Offline Soul Surfer

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Re: Why does this light make such a high pitch noise ?
« Reply #10 on: 07/12/2005 12:57:38 »
A vibrating source usually needs some sort of resonator to couple the sound into the air.  The higher the frequency the less important this is.  Examine the lamp carefully to try to find out the main source of the sound it may be necessary to take it apart.  Sometimes putting a soft washer between the transformer and its mounting or foam around the transformer coil could help but you will have to be careful to ensure that circuit elements fo not get too hot.

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ROBERT

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Re: Why does this light make such a high pitch noise ?
« Reply #11 on: 07/12/2005 16:32:00 »
quote:
Originally posted by Soul Surfer

quote:
Examine the lamp carefully to try to find out the main source of the sound it may be necessary to take it apart.


Before you take up SoulSurfer's advice, you should know that there is probably a large capacitior in your lamp,
 this will store electricity for days after you remove the batteries/power supply.
i.e. this device can give you an electrical shock even after you have removed the power source.

« Last Edit: 07/12/2005 16:32:24 by ROBERT »
 

Offline neilep

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Re: Why does this light make such a high pitch noise ?
« Reply #12 on: 07/12/2005 17:00:50 »
Thank you Ian and Robert for your insightful and helpful answers. As it's not possible for me to move next to a Pylon I have petitioned to allocate my road as a National Grid Power Station locale. My neighbours don't know it yet. I figured it will be a nice surprise for Christmas !

I wish I was brave enough to take my lamp apart and service it myself but I know that once I've done that, there is no way I'll be able to put it together in one piece.

I shall endeavour to put up with the noise....at least I know there is nothing wrong with it.

Thanks

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Re: Why does this light make such a high pitch noise ?
« Reply #12 on: 07/12/2005 17:00:50 »

 

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