the house already has ears
Simon Willison gave Claude Code ears to find a beep. A month earlier, we found one using ears the house already had.
Simon Willison had a mystery beep in his box room this week. He had Claude build Beep Locator. Phones, tablets and laptops join over a QR code, play chirps to each other to work out where they sit, then listen together. It placed the beep to within about 40 cm. Under that pile of boxes was an ancient carbon monoxide detector that wanted new batteries.
His line about it is the right one: “I think the most interesting part of this project is that I demonstrated it’s possible to give Claude Code ears.”
He’s right, and I can back him up from the other direction. In October we chased a beep of our own. Someone in the house heard one a little before midnight. We built no new hardware for it. The house already had ten microphones, in the security cameras, recording around the clock to a Shinobi NVR.
So the agent didn’t need ears. It needed permission to use the ones we had. It worked inside the recorder, wrote a tone detector, threw out the birdsong, and found one note: 3417 Hz for 0.87 seconds, heard by all six indoor cameras at once. A smoke alarm, about two metres from one camera.
Same problem, opposite ends. Simon built a sensor network for the question. We pointed the question at a sensor network that was already recording. Every tradeoff follows from that.
His listeners are live and calibrated. They chirp at each other, so they know where they are and can line up their clips in time. That’s how he gets to 40 cm. Ours are archival and dumb. The camera clocks drift by up to five seconds, so arrival time was useless, and the agent fell back on loudness. A 10 dB gap is a distance ratio, and two ratios draw two circles. That gets you two metres, which is enough to know which ceiling to look at.
His agent could move its ears around. Ours could only go back in time. That one cuts our way. The beep was over before anyone asked about it, and the recording was still there. Intermittent sounds are the hard ones, and you can’t set up phones fast enough for a beep that happens once.
Both of us ended up at the same kind of object: a household alarm, and a person who still had to go and look. He dug through boxes. Ours ends with a step stool.
Simon closes with “Figuring out ways to let coding agents perceive the world around them is a whole lot of fun.” Agreed. I’d add one thing. A lot of that perception is already installed. Cameras, doorbells, the UPS log, the thermostat. Most houses are full of sensors that record everything and never get asked a question. Building more of them is fun. Giving an agent read access to the ones you have, and one good question, is the cheaper trick.