Noisy LEDs (literally!)

I didn't realize that an LED could make *audible* sound until my friend/colleague Sajid called me over to have a look. What can I say - it's true.. This is a circuit with NO SPEAKERS, making audible sound.

Category:

Howto & Style

Tags:

• LED
• LEDs
• sound
• electronics
• DIY
• hack
• medialab

[danisdan01]

Are you sure its the LEDs themselves making the noise. Becuase from the sound of it, it sounds more like a transformer.

[davidjmerrill]

hmm - yes, you could be right about it being the transformer - I didn't home in on the source of the sound as carefully as I could have..

[ICintoTheFuture]

What is happening is that the power supply is dipping when all the LEDs switch on (higher current demand). You can see this as the LEDs dim. The click and HF whistle you hear are the windings in the transformer banging against each other. It is quite common in high current PSUs. The power supply is probably 'bursting'. ie switching at, say, 300kHz, but this 300kHz is happening in bursts. If the bursts are at 10kHz (the audio band) you will hear it. Add more decoupling or use more than 1 PSU

[baronmaniac]

I think the power supply is making that noise when the current load changes.

[KebyMilla]

Woah, blew my eardrums!

[madamerotten]

There may be either magnetostriction and/or electrostriction in some of the components. Given a sufficient step-change in applied voltage, many electronic components will have some mechanical displacement resulting in sound.

[Doublehp]

It's not the leds themselves that do the sound, but the current variations in various parts used for the leds: self, capacitors, wires, strips ... all have mechanical réactions (producing sound) when curent and voltage variations. Capacitive parts (including wires: conductors in front an other one) are subject to electro static repulsion; selfic parts (including wires that are twisted one around an other) are subject to magnetic fields.

All this make coper trying to move, and produce noise.

[maclover201]

It sounds like PWM.

[TheBypasser]

Well, in fact to prove the trannie part I'd say running a PWM driver made a PSU feeding the whole thing make an audible noise. More of it, usually it's made by any coils involved, like trannies, chokes etc.

[rminb010204]

LED efficiency is just too high, I doubt you will get much electrical potential becoming sound.

[sickliberty]

My first guess was that your device is using relays; ICinto also has a very good point. LED's don't make noise dude.

[luzgrioni]

it´s so good!