Paul Clark Triangulates Sounds with a GNSS-Based SparkFun Qwiic Sound Trigger Listening System
Built around a Sound Trigger board plus a GNSS-based high-accuracy timer, these sensors can triangulate any sound in 2D space.
SparkFun's Paul Clark has put together a tutorial on calculating the location of a sound, combining the company's SparkX Qwiic Sound Trigger board and a high-accuracy GNSS breakout board.
"The VM1010 [on the Qwiic Sound Trigger] is a clever little device which can be placed into a very low power 'Wake On Sound' mode," Clark explains. "When it detects a sound, it wakes up and pulls its TRIG (DOUT) pin high. The u-blox ZED-F9P GNSS receiver is an old friend. It is a top-of-the-line module for high accuracy GNSS location solutions including RTK [Real-Time Kinematic] that is capable of 10mm [0.39"], three-dimensional accuracy. Something that doesn’t get discussed as much as it should is that the ZED-F9P can also capture the timing of a signal on its INT pin with nanosecond resolution!"
Combining the two, Clark points out, gives you a noise-detection system that uses some clever code — and knowledge of the speed of sound — to calculate exactly where a sound is coming from in a given area. The trick: building not one, but two detectors.
"But how do we calculate the location if all we have is the time each sound trigger hears the footstep," Clark asks. "We have a ZED-F9P at each end and timestamp each trigger event very accurately. We can use the time difference to calculate the location, because we know how far apart the sound triggers are."
It's a clever approach, but one which can get expensive pretty quickly: Two sound locators, as used in the first part of Clark's tutorial, offers you positioning in terms of distance from the locators themselves; to get an actual two-dimensional location, you need to add a third locator and triangulate the signal.
While the Qwiic Sound Trigger, which is available while-stocks-last as board in SparkFun's experimental SparkX range, costs just $9.95 before volume discounts, the company's GPS-RTK-SMA ZED-F9P breakout is a hefty $274.95 — making the two-dimensional sound locator bill of materials $854.70 before you even add microcontroller boards.
Both the one-dimensional and two-dimensional sound locator projects, with source code and links to purchase the parts, are now available on the SparkFun tutorials site.