experiment for speed of sound

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Speed of sound.

Experiment #33 from Physics with Vernier

Introduction

Compared to most things you study in the physics lab, sound waves travel very fast. It is fast enough that measuring the speed of sound is a technical challenge. One method you could use would be to time an echo. For example, if you were in an open field with a large building a quarter of a kilometer away, you could start a stopwatch when a loud noise was made and stop it when you heard the echo. You could then calculate the speed of sound.

To use the same technique over short distances, you need a faster timing system, such as a data-collection interface. In this experiment, you will use this technique with a Microphone connected to an interface to determine the speed of sound at room temperature. The Microphone will be placed next to the opening of a hollow tube. When you make a sound by snapping your fingers next to the opening, the computer will begin collecting data. After the sound reflects off the opposite end of the tube, a graph will be displayed showing the initial sound and the echo. You will then be able to determine the round trip time and calculate the speed of sound.

Measure how long it takes sound to travel down and back in a long tube.
Determine the speed of sound.
Compare the speed of sound in air to the accepted value.

Sensors and Equipment

This experiment features the following sensors and equipment. Additional equipment may be required.

Correlations

Teaching to an educational standard? This experiment supports the standards below.

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Purchase the Lab Book

This experiment is #33 of Physics with Vernier . The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.

Speed of sound

I can measure the speed of sound waves in air using an echo method.

Lesson details

Key learning points.

The ‘speed of sound’ is the distance travelled by a sound wave pulse every second, measured in m/s.
Sound wave speed depends on the medium: it is about 340 m/s in air, faster in liquids and faster still in solids.
Sound waves can reflect from hard surfaces, travel back and be heard again (an echo).
The speed of sound waves (or the distance they travel) can be calculated using the equation: speed = distance ÷ time.
In an experiment, measuring longer distances and times means any errors are a smaller proportion of the measurements.

Common misconception

High pitched sounds (higher frequency sound waves) travel faster than low pitched sounds (lower frequency sound waves).

Take measurements for the speed of sound using a high-pitched blast of a whistle as well as the lower pitched sound of hitting pieces of wood together to show they are the same (within error).

Speed - how fast something is moving, often measured in metres per second

Sound wave - a ‘pulse’ that travels through a material caused by forward and backward vibrations of particles

Medium - the material through which a wave travels

Frequency - the number of vibrations each second

Echolocation - a method of detecting distances to objects by making a sound and waiting for an echo to return

a long tape measure or trundle wheel, timer, blocks of wood, whistle, a suitable outdoor space with a large distance (over 80 m) and a large, hard vertical wall

Content guidance

Risk assessment required - equipment

Supervision

Adult supervision required

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