Nature of SoundNature of Sound

By Group 3IV-St. Catherine

The speed of light in a vacuum is 299,792,458 meters per second or 186,000 miles per second (669,600,000 mph), which is roughly 870,000 times faster than the speed of sound.This means that light travelsfaster than sound.

CAN SOUND TRAVEL IN WATER?

IS THERE SOUND ON THE MOON?

• the sensation produced by stimulation of the organs of hearing by vibrations transmitted through the air or other medium

• it is an ENERGY

• Any sound that you hear as a tone is made of regular, evenly spaced waves of air molecules.

NOISE

TONE

How is sound produced?

• Vibration and particles of fluid• Source of sound Vibrations in molecules

in all directions ear eardrums

How is sound transmitted?

• Through vibrations• Travel in air, liquid, gas• They do not travel in vacuum and so they do

not travel in SPACE!

Wavelength• spacing of the waves -

the distance from the high point of one wave to the next one

Speed is not the same with frequency

• Frequency refers to the number of vibrations that an individual particle makes per unit of time (how often)

• speed refers to the distance that the disturbance travels per unit of time (how fast)

Intensity

• amount of energy flowing per unit time over an area

• depends on the amplitude and the distance of the observer from the source

Loudness• subjective response that will vary with a

number of factors.• scale extending from 'soft' to 'loud.‘• measure of the response of the ear to the

sound

• Sensation of a frequency• High pitch = High Frequency• Low pitch = Low Frequency

Speed of Sound Waves in Solids, Liquids and Gases

Speed in Solids > Speed in Liquids > Speed in Gases

Why? This is because molecules in a

solid medium are much closer together than those in a liquid or gas, allowing

sound waves to travel more quickly through it

The Quality of Sound• TIMBRE - Timbre is what makes a particular

musical sound different from another• Musical instruments

FACTORS AFFECTING WAVE SPEEDFACTORS AFFECTING WAVE SPEED

1. Properties of medium1.1 Elastic properties – maintaining the

object’s shape (no deformation) when force is applied.

- fastest in solids, then liquids and lastly in gases

1.2 Inertial properties – tendency to be lethargic in its state of

motion- includes mass and density- sound will travel more faster in a less

dense material than in a more dense material.

2. Properties of air, temperature and humidity

Speed of sound waves at different temperatures

• Higher Temperature = Faster sound waves

• Lower Temperature = Slower sound waves

Why? :/

• At lower temperatures the air is denser and therefore harder to travel through

Speed of sound in air= 331 m/s (at 0˚C)

Speed of a sound wave

• Speed of a sound wave refers to how fast the disturbance is passed from particle to particle.

• v = 331 m/s + (0.6 m/s/C) * T

In Celsius (C)

Speed vs. Distance

• Directly proportional

•As speed increases, the distance covered increases too.

Example:

Determine the speed of sound on a cold winter day (T=3 degrees C).

Example:SOLUTION:

given: Temperature = 3˚C

v = 331 m/s + 0.6 m/s/C * T = 331 m/s + 0.6m/s/c * 3˚C = 332.8 m/s

• doubling of the wavelength results in a halving of the frequency; yet the wave speed is not changed

• Speed = Wavelength * Frequency • v = f • λ

Unit: Hertz (Hz)

ANOTHER EQUATION TO DETERMINE THE SPEED

EXAMPLE

• Playing middle C on the piano keyboard produces a sound with a frequency of 256 Hz. Assuming the speed of sound in air is 345 m/s, determine the wavelength of the sound corresponding to the note of middle C.

EXAMPLE • Solution:

Given: frequency = 256 Hzspeed of sound in air = 345 m/swavelength = ?

speed = wavelength * frequencywavelength = speed/frequency

= 345 m/s / 256 Hz = 1.348 m = 1.35 m

IMPORTANT USES OF SOUNDIMPORTANT USES OF SOUND

Important uses of SOUND

• Ultra Sound tests - diagnostic imaging techniques to create images of

blood vessels, tissues and organs- Pregnant women -Aid detection of heart disease, tumors, gallstones, etc

STETHOSCOPE-HEAR THE INTERNAL SOUNDS OF BODY.

-AMPLIFIES THE SOUND INSIDE YOUR BODY.

THE END THE END

In fluids… In solids…

• Pressure-pulse or compression-type wave -Sound wave that travels in fluids (liquid, gases)

• Transverse wave – the sound wave that travels in solids.

The Doppler Effect

• named after a scientist, Christian Doppler.