Sound to LED

Hi, I would like to know if anyone has made an LED flash (like a metronome) from the output of a computer notebook?
ie plug a cable into the headphone socket of a notebook and have an external LED flash in time to the metronome on the book.
Can anyone help? or point me in the right direction?
Peter

Do you want to make a metronome with your laptop? Not sure what you mean by "metronome on the book"; are you referring to the [sheet] music tempo?

I have a metronome that runs on my notebook, it also gives an audible sound and can be heard through the headphones. What I want to do is make that audible sound into a LED flash so plug a 3.5 mm plug into the computer and have the LED flash externally.

Ok. It's possible that the headphone output voltage is high enough to light the LED on its own. You can try connecting two LEDs in parallel, with the anode of the first LED connected to the cathode of the other LED, and anode of the other connected to cathode of the first. The paralleled LEDs then connect to the speaker output. You can also replace one of the LEDs with a diode, e.g. 1N4148.

Thanks, I will try and let you know the outcome!

download a frequency generator and crank the volume!