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Echo technology: parking sensor and echo sounder

About this app

People copy the bat: a parking sensor sends ultrasound and beeps faster the closer the wall gets, until it becomes a continuous tone. A boat with an echo sounder sends pulses into the water, hears the fish before the bottom and draws the depth on its screen. Plus: sound is more than four times as fast in water as in air.

With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.

The idea

People copied echolocation from bats. A parking sensor has small ultrasound sensors in the bumper. They send a short pulse, usually around 40 kilohertz, and measure when the echo comes back from the wall. The shorter the time, the closer the wall. An echo sounder on a boat does the same in water. There sound travels about 1500 metres per second, more than four times as fast as in air. The time until the echo from the bottom gives the depth of the water.

What the app shows

In the “Parking” scenario a car reverses towards a wall. A pulse travels in slow motion from the sensor to the wall and back. Below you see what the driver hears: the closer the wall, the closer together the beeps, and below 30 centimetres they become a continuous tone. In the “Echo sounder” scenario a boat travels over the bottom and a shoal of fish. The echo from the fish arrives before the echo from the bottom, and a screen records the depth profile.

Try it together

Let your child roll the car to different spots with a tap and say beforehand whether the beeping will get faster or slower. With “Beeping on” you really hear the warning tones. Then head out onto the water: the boat sets off, and the bottom with fish arches appears on the screen. A card compares how fast sound is in air and in water. Something to talk about: what do the bat, the car and the boat have in common?

Frequently asked questions

How does a parking sensor work?
Ultrasound sensors in the bumper send short pulses and listen for the echo. From the time until the echo the car works out the distance to the obstacle. A warning tone beeps faster the closer the obstacle is and becomes a continuous tone when it is very close.
Can you hear the ultrasound of a parking sensor?
No. The sensors work at about 40 kilohertz, far too high for our ears. What you hear in the car is a separate warning tone produced by the control unit.
How does an echo sounder measure water depth?
A transducer under the boat sends a sound pulse downwards, and the bottom reflects it. Because sound travels about 1500 metres per second in water, an echo after 20 thousandths of a second means a depth of 15 metres. Fish with a swim bladder send back their own, earlier echo.
What can my child try in the app?
Your child reverses the car into the space and sees and hears the beeping get faster. A single ultrasound pulse can be followed in slow motion. On the water the boat passes over a shoal of fish, and the echo sounder screen records the bottom and the fish. A guided explanation mode walks through the scene.

Subject: Elementary · Science & Society

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