How to find acoustic speed

How to find acoustic speed

Today know practically everything that the sound in the environment extends with some final speed. It can be measured, having compared the speed of its distribution in air to light flash which can be considered instant or on an echo. Acoustic speed in various environments can be calculated theoretically.

It is required to you

  • - range finder;
  • - stop watch;
  • - a formula of gas in which acoustic speed is measured.


1. Acoustic speed can be measured in air by two rather easy ways. Take a fowling piece as a sound source. You conduct experiment in twilight that the flame from a shot was well visible. Depart from the person with a gun on distance about a kilometer so that between you there were no barriers. Take an exact stop watch and after a shot which can be marked on flash of powder gases, measure time for which the sound will be heard. Find acoustic speed, having divided distance for a while for which it is passed by vzv =S/t sound. What will be a distance, there more precisely measurement more. Repeat experiment several times then find average value.

2. Acoustic speed can be measured if to become before a big firm barrier what can be, for example, the mountain or the steep. Become at some distance from it, measure distance by means of a range finder. Then make a sharp loud sound (shot, blow of a bell, etc.), having at the same time included a stop watch. Switch off it when you hear the reflected sound. Find acoustic speed, having divided the doubled distance to a barrier into the measured vzv =2 time • S/t. Take measurement several times and find average value.

3. To calculate acoustic speed in gas theoretically, take its temperature, molar weight and learn a chemical formula. Transfer temperature to Kelvins, having added number 273 to degrees Celsius. Depending on a chemical formula of gas pick up adiabatic curve coefficient. For one-atomic gas it is equal 5/3, for diatomic gas - 7/5 and for other gases - 4/3. Increase adiabatic curve coefficient by 8.31 (a universal gas constant) and absolute temperature, divide into molar weight in kg/mol. Take a root from the received number square.

4. To determine acoustic speed in sea water at a temperature of T which is taken in degrees Celsius at Z depth, at salinity of S in per mille, use the equation of vzv of =1492.9+3•(T−10) (−0.006•T−10) ²−0.04•T−18)² + 1.2•(S−35) −0.01•(T−18)·(S−35) +z/61.

Author: «MirrorInfo» Dream Team