ANALYSING SOUND WAVES

THE NATURE OF SOUND WAVES

Sound is a form of energy propagated as waves that make our

eardrums vibrate.

Sound waves are longitudinal waves which is required a medium for

its propagation.

Sounds are produces by vibrations such as the vibrations of the

cone-shaped diaphragm of loudspeaker, guitar strings, column of air

in a musical instrument a tuning fork

Sound waves cannot travel in a vacuum because there is no

medium(particles) through which the sound energy can be

propagated.

When a tuning fork vibrates, layers of air vibrate and the sound energy is propagated through the air around it in the form of waves.

• When the tuning fork moves forwards, the air is compressed.

• When the tuning fork moves backwards, the air layers are pulled apart and cause a rarefaction.

• Therefore, a series of compression and rarefactions will produce sound.

How is sound produced by a vibrating objects?

The air particles vibrate backward and forward in the direction

parallel to the direction of propagation of the sound wave.

• Wavelength of sound, λ = the distance between two

successive regions of compression or two successive regions of

rarefaction.

Why does sound waves is a longitudinal waves?

The speed of sound, v in a medium can be determined using

the formula

The speed of sound in solid is greater than the speed of

sound in liquids which is greater than the speed of

sound in gases.

The speed of sound is unaffected by pressure.

The speed of sound increases with temperature.

SPEED OF SOUND

Sound waves travel faster insolid > liquid > gas

LOUDNESS & AMPLITUDE OF SOUND

The loudness of a sound is considered to be high or otherwise depending on the hearing ability of a person.Loudness is influenced by the amplitude of the sound wave.

PITCH & FREQUENCY OF SOUND

The pitch of a sound or a musical note is an

indication of how high or low the sound is.

The pitch of a sound is determined by its frequency

:

a high pitch corresponds to a high frequency.

APPLICATIONS OF SOUND WAVESCleaning with Ultrasonic Waves - Dentist use ultrasonic waves to removes plaque from teethLocating an object under water - SONAR is a system used to detect underwater objects or to determine the depth of the water by mean of an echo. - Ultrasound signal is sent out from a transmitter. - Its echo from the seabed is detected by a receiver which is connected to an electrical recording circuit. - The time interval, t between the sending and receiving of the ultrasound signal after reflection from the seabed is measured.

Disintegration of kidney stones - sound waves of high energy are directed at the kidney stones to destroy them in the cavity of the kidney. A bat can navigate in darkness

When ultrasonic waves emitted by the bat hit an object, they are reflected back and received by the bat.

The time between the emission of the sound waves and reception of the reflected waves enables the bat to estimate the position of the object accurately.

This enables the bat to adjust its direction to avoid knocking at the object.

CALCULATING DIS TAN CES USING THE REFLECT ION OF SO UND WAVES

d = distancet = time interval between the instant the sound is emitted to the instant the reflected sound returns to ranging device.v= speed of sound

EXAMPLE

1. a student is standing at a

distance of 45 m from a wall. He

gives loud clap and the echo is

heard after 0.3 s, calculate the

speed of sound in air.

An ultrasonic wave is used to determine the depth of a seabed. A pulse of ultrasound is generated and travels to the seabed and reflected by it. The time taken by a pulse of ultrasonic wave to travel to and fro the seabed is 0.28 s. It the speed of sound in the water is 1 500 ms-1, calculate the depth of the seabed.