Late last night one David Grossman shared with me a different sort of laser singing. Instead of using the pitch of the laser to replicate sound the way DePrisco did with the fiber laser, Grossman transformed his 250 watt CO2 laser into a working speaker.
David explains: "In essence, the laser is firing at a fixed repetition rate - there's around 30k pulses hitting the material every second. Each of those pulses disrupts the material, and has an associated flash of light and plume of ejected material, which pushes air outwards, making a sound.
"The circuit that's driving the laser pulsing is using the audio signal to vary the energy of each of those pulses.
As such, each plume is ejecting a different amount of material, which is also pushing air differently, causing different sounds."
To put it simply, the music is being played by tiny explosions.
As I prepared to write up Grossman's video, I got another email, this time from the original laser Portal engineer.
Chris DePrisco was dropping me a line to let me know he had followed up on the :Still Alive" video with a two-track fiber laser version of "Want You Gone". Using his single laser he recorded two tracks and spliced them together into one slightly-off but still incredible impressive video.
I couldn't decide which to post, so I posted them both. That I live in a world where such decisions are necessary pleases me to no end.