Experiment 7

Speed of Sound

The Nature of Sound Waves

1. A wave is a traveling disturbance.

2. A wave carries energy from place to place.

The Nature of Sound Waves

Transverse Wave

The Nature of Sound Waves

Longitudinal Wave

Periodic Waves

Periodic waves consist of cycles or patterns that are produced over and

over again by the source.

In the figures, every segment of the slinky vibrates in simple harmonic

motion, provided the end of the slinky is moved in simple harmonic

motion.

In the drawing, one cycle is shaded in color.

The amplitude A is the maximum excursion of a particle of the medium from

the particles undisturbed position.

The wavelength is the horizontal length of one cycle of the wave.

The period is the time required for one complete cycle.

The frequency is related to the period and has units of Hz, or s-1.

Tf

1

Periodic Waves

fT

v

The Nature of Sound Waves

LONGITUDINAL SOUND WAVES

The Nature of Sound Waves

The distance between adjacent condensations is equal to the

wavelength of the sound wave.

The Nature of Sound Waves

Individual air molecules are not carried along with the wave.

The Nature of Sound Waves

THE FREQUENCY OF A SOUND WAVE

The frequency is the number of cycles

per second.

A sound with a single frequency is called

a pure tone.

The brain interprets the frequency in terms

of the subjective quality called pitch.

The Nature of Sound Waves

THE PRESSURE AMPLITUDE OF A SOUND WAVE

Loudness is an attribute of

a sound that depends primarily

on the pressure amplitude

of the wave.

The Speed of Sound

Sound travels through gases,

liquids, and solids at considerably

different speeds.

The Speed of Sound

Conceptual Example Lightning and Thunder

The Speed of Sound

SOLID BARS

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Applications of Sound in Medicine

By scanning ultrasonic waves across the body and detecting the echoes

from various locations, it is possible to obtain an image.

Applications of Sound in Medicine

Ultrasonic sound waves cause

the tip of the probe to vibrate at

23 kHz and shatter sections of

the tumor that it touches.

Applications of Sound in Medicine

When the sound is reflected

from the red blood cells, its

frequency is changed in a

kind of Doppler effect because

the cells are moving.

Activity 1: Velocity of Sound in Air

Temperature of air = Diameter of Resonance Tube =

Tuning Fork Wavelength (m) Average

Wavelength

Experimenta

l speed

Theoretical

speed

% error

Trial 1 Trial 2 Trial 3

DL 3.04

Tube open at one end

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Activity 1: Velocity of Sound in Air

DL 3.04

Activity 2: Speed of Sound (Expt. 24 of Physics with Computers)

Trial Total Travel Time

1

2

3

Average

Experimental speed

Theoretical speed

%error

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Activity 2: Speed of Sound (Expt. 24 of Physics with Computers)

Activity 3: Velocity of Sound in Solid

Average of distances between node to node

Wavelength of sound in air

Frequency of sound in air

Frequency of sound

Length of rod

Wavelength of sound in air

Experimental speed of sound in the rod

Theoretical speed of sound in the rod

% error

Activity 3: Velocity of Sound in Solid

Lr 2

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