Locating the source of a mysterious beep
Simon Willison tackled the classic "mysterious beep" problem by building Beep Locator, a multi-device acoustic triangulation system powered by AI. This creative solution, developed interactively with Claude Code, exemplifies practical problem-solving using modern web tech and AI agents, making it a hit for HN's DIY and AI enthusiasts.
The Lowdown
Simon Willison, exasperated by an intermittent, untraceable beep emanating from a box-filled room, embarked on a mission to permanently solve this domestic auditory enigma. Instead of manual box-digging, he collaborated with Claude Code to develop "Beep Locator," a sophisticated system designed to pinpoint the source.
- The system leverages a Python web server as its core, coordinating multiple 'listener' devices—such as phones, tablets, and laptops—connected via WebSockets.
- Devices either self-locate by playing sounds to each other or are manually positioned in a 'rough mode' on a UI map.
- Equipped with browser microphone access, listeners continuously buffer audio and employ Fast Fourier Transform (FFT) and high-pass filters to detect potential beeps.
- When a beep is reported, the system aligns audio clips from all devices using a strategically played chirp, allowing for precise triangulation.
- Users can mark confirmed mystery beeps, enabling the system to learn its frequency and interval, refining its location estimates.
- Ultimately, Beep Locator successfully pinpointed the source to an ancient, low-battery carbon monoxide detector, solving the immediate problem.
- The underlying acoustic localization principles are inspired by a 2007 paper, "BeepBeep: A High-Accuracy Acoustic-Based System for Ranging and Localization Using COTS Devices."
- A key innovation was "giving Claude Code ears": by having the AI agent dynamically update client-side JavaScript over WebSockets, Claude could essentially analyze audio feedback and self-reconfigure its "senses" to better solve the problem.
This project highlights a fascinating frontier in AI development: enabling coding agents to perceive and interact with the physical world, turning abstract problem-solving into tangible, real-world solutions.
The Gossip
Pragmatic Picks vs. Ponderous Projects
Many commenters proposed simpler, more manual approaches to finding the elusive beep, ranging from the straightforward 'just unpack the boxes' to a 'physical binary search' method of elimination. Other suggestions included simply timing the intervals between beeps for a more focused search. Simon Willison clarified his motivation was to 'solve this class of problem forever,' indicating a preference for a reusable technical solution over a one-off manual effort, sparking a discussion about when to engineer an elaborate solution versus when to just get it done. The thread also featured amusing self-deprecating remarks about missing the solution clearly stated mid-article.
AI's Analytical Acumen
A lively debate emerged regarding the efficacy of AI in critical thinking and problem definition. One user expressed skepticism about AI's ability to reason, criticizing the practice of having AI generate problem statements ('problems.md') and dismissing such outputs as 'AI-slop.' The author, Simon Willison, countered by asserting that advanced AI models like Opus 5.5 and Fable 5.2 are indeed capable of effective reasoning, especially within an iterative development process, where the model can take on significant judgment roles in guiding the project to its successful conclusion.
Acoustic Array Alternatives
Commenters shared various existing and DIY options for acoustic localization, demonstrating widespread interest in specialized sound-finding tools. Several users highlighted commercial acoustic imaging cameras, noting their decreasing costs and practical applications for tasks like identifying air leaks. Others pointed to specific microphone arrays, like the miniDSP UMA 16, as viable components for building personal acoustic cameras or suggested rental services for professional-grade equipment, reflecting a growing accessibility and utility in this niche technology.
Beeping Bane Battles
A significant thread of conversation revolved around the shared exasperation caused by mysterious beeps. Many users recounted their own maddening experiences with hard-to-locate sounds, often tracing them back to low-battery smoke or carbon monoxide detectors hidden in obscure places. This led to discussions about device design, with suggestions for manufacturers to make beeps more directionally identifiable or to use gradual ramp-ups/downs to prevent precise timing. The topic also veered into the realm of prank devices like 'annoyatrons,' which exploit the very human vulnerability to persistent, irritating sounds.