sound

form of energy produced by the vibration of an object.

tuning fork (what it is)

a U-shaped metallic device with 2 arms called prongs.

tuning fork (how it makes sound)

When the prongs are struck against a rubber pad, the prongs vibrate, causing sound.

larynx

sound is produced in humans by the vocal cords of the larynx.

vocal cords

two ligaments stretched across the voice box leaving a narrow slit for air to pass through.

string instruments

instruments that produce sound when their strings vibrate.

wind instruments

instruments that produce sound when air passes through the cavities and the column of air vibrates.

percussion instruments

instruments that produce sound when the membrane stretched tightly is struck.

reed instruments

instruments that produce sound when air passes through the instrument, which vibrates the metal reeds.

how does sound propogate

When a body vibrates, it transfers its energy to its surroundings, causing nearby air particles to vibrate. These molecules pass the energy to their neighbouring molecules.

how is a wave formed

When a body vibrates and transfers energy to the surrounding particles, the particles vibrate about their mean positions. This disturbance of air particles constitutes a wave, which then reaches our ears and our brain processes it.

transverse waves

waves that are produced perpendicular to their source. Ex: light

longitudinal waves

waves that are produced in the same direction as their source. Ex: sound

does sound need a medium to propogate

Yes, as the particles that vibrate actually carry the sound, and this cannot take place in the absence of these particles.

best medium for sound to propogate

solid

worst medium for sound to propogate

gas

compressions

regions in the air where the particles are pressed together when vibrating.

rarefactions

regions in air where particles are spread apart when vibrating.

wavelength

distance between 2 compressions or 2 rarefactions. unit= lambda SI unit=m

amplitude

displacement of a crest or trough from the mean position. unit= angstrom SI unit= m

time period

time taken to complete one wavelength unit= second

frequency

no. of waves completed in 1 second unit= hertz frequency= 1 ____________ time period

loudness

intensity of the sound unit= decibel

will a wave with lower energy be louder than one with more energy?

no, as loudness of a sound is proportional to the energy of the wave

what is loudness dependant on?

It depends on amplitude, distance from the vibrating body, and the surface area of the vibrating body.

pitch

characteristic of sound that helps us differentiate between a shrill sound or a flat sound.

What does pitch depend on

it depends on frequency, length, mass, and tightness of the body

speed of sound

distance _________ time

speed ^2

density _________ elasticity

speed of sound at 0 degrees C

331 m/s

speed of sound at 20 degrees C

343 m/s

speed of sound at -40 degrees C

306 m/s

speed of sound at room temperature

340 m/s

laws of reflection of sound

1. angle of incidence = angle of reflection 2. the incident sound wave, the reflected sound wave, and the normal all lie on the same plane.

echo

the reflection of sound waves on hitting a reflecting surface. echo= 2 distance ____________ time

conditions for an echo to be heard

a. there should be a reflecting surface b. there should be a minimum distance of 17 m from the reflecting surface and the source of sound. c. the sound should be loud d. the sound should reach our ears after 0.1 sec

persistence of hearing

the phenomenon caused by our brain's inability to distinguish between a sound and it echo when the echo occurs less than 0.1 seconds after the actual sound.

sonar full form

SOund Navigation And Ranging

sonar device function

used to determine the depth of seas and oceans.

how do sonar devices work?

They transmit a pulse of sound, and these waves are reflected by the seabed. they then take the time it took to reflect and determine the depth.

good reflectors of sound

hard and smooth surfaces, like cement walls, metals

bad reflectors of sound

soft and rough materials like paper, cloth, asbestos

how do absorbers of sound reduce the amplitude of a material

they reduce the energy of a material

soundproof box

an enclosure that neither lets its sound outside nor lets outside sound in

how do you make a soundproof box

a. it should have wooden flooring and thick curtains. b. the floor should have thick carpeting c. roof should be made of plaster of paris or thermocol. d. there should be care taken to prevent use of machinery as machines produce a lot of sound.