Summer time will not be fairly over simply but, however it’s beginning to sputter right here within the Northern Hemisphere. For a lot of, meaning placing the seashore chairs and coolers in storage in preparation for the approaching winter. Of their place, ice shanties, skates, and different wintertime toys will quickly begin to reemerge. And with the arrival of that season as soon as once more comes the necessity for reminders about ice security.
Plenty of enjoyable and sport may be had on the floor of a frozen lake, however there’s additionally loads of hazard if that sheet of ice shouldn’t be thick sufficient. Hundreds of individuals die after unexpectedly plunging into an icy physique of water yearly. To stop these tragedies, the thickness of ice is usually measured by chiseling a gap in it and utilizing a tape measure. This methodology is liable to error, nonetheless.
The system design (📷: C. Lin et al.)
Extra correct measurement strategies, like ground-penetrating radar, are additionally out there. Nonetheless, the devices value tens of hundreds of {dollars} and require specialised coaching to be used, so they’re hardly ever used for recreation. Engineers on the Dalian College of Expertise have give you an answer that would supply the accuracy of applied sciences like radar with the benefit and low value of a tape measure. They’ve developed a technique that turns a smartphone into an ice thickness sensor that leverages acoustics.
The system, referred to as IceSound, makes use of the cellphone’s built-in speaker to emit a specifically designed chirp sign spanning from 3 kHz to 22 kHz. When the sound waves journey by way of the ice, they bounce off two key boundaries — the air-ice interface on the floor and the ice-water interface on the backside. The smartphone’s microphone then picks up these echoes. By calculating the time delay between the reflections, the app can decide the ice’s thickness utilizing a system primarily based on the velocity of sound in ice.
Nonetheless, that is harder in apply than in idea. Sound travels by way of ice a lot sooner than by way of air (about 3,250 m/s at 0 levels C) making it tougher to tell apart between the carefully spaced echoes. Thick ice additionally weakens the underside reflection, making it troublesome to detect. And since sound velocity varies with temperature, starting from 3,250 m/s close to freezing to round 3,800 m/s at -30 levels C, merely assuming a continuing worth may result in massive errors. Moreover, the cellphone’s orientation issues. If the speaker and microphone should not pointed instantly on the ice floor, the outcomes may be skewed.
The approach was validated in a sequence of experiments (📷: C. Lin et al.)
To beat these obstacles, IceSound layers in some intelligent engineering. Sign processing strategies like wavelet denoising, high-pass filtering, and mixing a number of measurements assist tease out the faint backside echo from background noise. For thicker ice with distinct echoes, the system depends on time-domain correlation to extract the delay; for thinner ice, the place echoes overlap, frequency-domain evaluation proves more practical. To take care of temperature variations, the app integrates information from public climate APIs, which it makes use of to mannequin how sound velocity adjustments with depth. The smartphone’s accelerometer and magnetometer additionally present orientation information in order that the app can compensate for tilt.
In area trials, IceSound achieved a imply absolute error of simply 0.3 centimeters when measuring ice within the essential 10-15 cm vary. Extra importantly, when assessing whether or not the ice was protected for human exercise, the system’s error charge dropped to only 0.13%.
By turning a tool practically everybody already carries into a robust ice security instrument, IceSound may make winter sports activities and recreation a lot safer. As a substitute of lugging round an auger, chisel, or radar rig, future skaters and ice fishers might solely want to drag out their cellphone, run an app, and know inside seconds if the floor beneath their ft is protected.
