Echo - Calculate Distance to Reflector

Stopwatch and calculator for calculating how long it takes for the echo or how far away the sound-reflecting surface is. In one second, the sound travels about 343 meters, for the echo the sound has to go back and forth, so the time measured is twice as long. If you hear the echo after a second, the reflector (e.g. wall or mountain) is almost 172 meters away.

The calculator can also be used without the stopwatch. For this, simply enter one of the two values and press Calculate.

In an echo, sound is reflected by an obstacle and returns, at least partially, to its source. The echo is of course more quiet than the original sound. Depending on the arrangement of the reflecting obstacles, multiple echoes can occur, each becoming increasingly quieter. Obstacles that produce a good echo are surfaces that are as smooth and hard as possible, ideally perpendicular to the direction of sound wave propagation, so that the reflection returns directly to the source.
Sound waves propagate spherically through the air from their source, at least when that source is at rest. These sound waves are alternating differences in air pressure. The differences in air pressure are tiny; for a sound of 80 decibels, they are around 0.2 pascals, which is approximately 0.0002 percent of the normal air pressure of 1013 hectopascals or millibars. Nevertheless, we can hear these differences clearly. Sound needs a medium to propagate, which can be air, but also water or something else. This doesn't work in a vacuum. The speed of sound depends on the medium; in water, for example, it is much higher than in air. Sound in water, for example, is used in sonar. This calculator can only work with sound in air. For calculations with other sound speeds, see Calculating the speed, duration, and distance of sound.

Physics commonly uses SI units. Here is a calculator to convert units.