Sound and

Communication

Sound is caused when vibrations make air move and vibrate.

This causes sound waves which are picked up by your eardrum causing it to vibrate.

This is translated by your brain into a recognized sound.

• Sound needs a medium to travel on such as gas, solid or liquid.

• Sound travels in air at about 1,224 km per hour. It travels much faster in water at about 5,400 km per hour.

• An echo occurs when a sound bounces off a surface and comes back to you.

A large vibration causes a large sound and a small vibration causes a small sound.

Sound can also be caused by energy.

Energy causes vibration which causes sound.

• Vibrations were used by North American Indians to track buffalo. They would put their ears to the ground to try and hear the buffalo.

• Soft materials such as cotton wool absorb sound, this is why you cannot hear anything when you drop them

An Ancient Greek Philosopher called Aristotle believed that sound and light were carried through air like waves.

He believed that they couldn’t travel through a vacuum.

Many centuries later scientists could create a vacuum to test Aristotle’s theory.

An Irish scientist called Robert Boyle created an experiment in 1658.

He pumped air from a jar that held a ticking watch. This created a vacuum.

As there was no air left in the jar, he could not hear ticking at all. This proved Aristotle’s theory correct

Sound Intensity

• Decibels are used to measure the intensity of sound (how powerful a sound is)

• If something is 0 decibels it is not powerful enough to be heard.

Whispering 10 decibels.

Wind and leaves rustling

20 decibels.

Waves on the seashore

40 decibels.

A shouted conversation

70 decibels.

A vacuum cleaner 80 decibels.

Rock music 100 decibels.

A jet engine 110 decibels

The threshold of pain

120 decibels!

The Ear

Anatomy of the Ear

Your Voice Box – the LarynxThe larynx is another name for the voice box. The

larynx is made up of nine parts of cartilage and it has two main parts.

When you are swallowing the epiglottis which is the upper cartilage covers the voice box to stop food going down into the lungs.

Whenever you aren’t swallowing food the epiglottis opens and the larynx opens as well.

The larynx plays an important part in voice production.

Sound is produced when the vocal cords vibrate as air flows out of the lungs.

The adam’s apple is in front of the larynx. When boys reach their teenage years the larynx grows and that causes their voice to deepen.

Sound Waves

• Sound Waves: A vibrating object gives off sound waves and different vibrating objects can give off different amounts of sound waves.

• Ultrasonics is the study of high-frequency sound waves.

• Frequency: Frequency is the number of sound waves given off by a vibrating object.

• Measuring Sound Waves: Frequency is measured in Hertz (Hz for short) which is the number of sound waves given off by a vibrating object per second.

• An echo happens when a sound bounces off a surface and bounces back to you.

• A large vibration causes a large sound and a small vibration causes a small sound.

• Soft materials such as cotton wool absorb sound.

• Indians used vibrations to track buffalo. They would put their ears to the ground to try and hear the buffalo.

Sound in Water

Sound travels faster through water than through air. This helps animals such as whales to communicate or talk with each other over very long distances. Whales also use sound waves to help them travel through dark water. They send and receive sound waves in the same kind of way as the sonar on a ship or submarine.

Animal Sounds• Dolphins use echolocation to communicate, to

locate fish and to detect underwater obstacles. • Echolocation is a loud clicking sound produced

by dolphins.• The clicking sound bounces off objects which

causes an echo. • Dolphins can communicate to each other over

hundreds of kilometres. Dolphins produce clicking sounds from an organ called a melon on their head.

• Humans can hear millions of sounds, from screams to the hissing of a cat, but there are some sounds that are far too high-pitched for humans to hear.

• Some animals including dogs can hear these high-pitched signals.

• Whales use this method to see, by sending the signal against the sea-floor. It then bounces back to them, telling them where they are located.

• Some whales sing songs which can be heard throughout the oceans.

• A male humpback whale has it’s own song which will last for 35 minutes.

• Fishermen have copied this method. If it was a foggy night and they couldn’t see and they knew there were cliffs ahead they would shout out.

• An echo would come back to them. They would start counting after they shouted out.

• If it took 5 seconds they were one mile away, 10 seconds if they were two miles away etc.

Animal Hearing

• Bats can fly in total darkness. They can do this by screeching out a very high pitched note. Humans cannot hear this high pitched sound and ultrasonic sound.

• Bats can hear up to 120,000 hertz. A young person can hear up to 20,000 hertz. Some notes and sounds are just too high for humans to hear.

• Many animals can hear a lot better than humans

Bats Up to 120 000 Hertz

Mice Up to 100 000 Hertz

Dogs Up to 35 000 Hertz

Cats Up to 25 000 Hertz

People Up to 20 000 Hertz

Animal Hearing

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Ultrasound

• Hospitals use ultrasound to see babies in a mother’s womb.

• They send the signal into the mother’s womb. It bounces off the baby and goes back out.

• The hospital then puts this picture on a special camera, allowing the family to see the baby

• Sound waves make their way through the ear canal. The waves then go into the ear drum. The ear drum is very thin.

• The Ear drums vibrate when the sound waves arrive.

• The sound waves go through three small bones, the hammer, anvil and stirrup. They are called the ‘ear ossicles’. They bring the sound waves through a small space of air. It is called the ‘Middle Ear Cavity’.

• The sound waves then travel through the oval window to fluid in the inner ear. This fluid is called the endolymph. The sound waves make the endolymph fluid move. This causes tiny hair cells and the cochlea to vibrate.

• The hair cells are called hair cells because they look like tiny little hairs. The vibrations of the hair cells and the cochlea send messages to the auditory nerve.

• The auditory nerve brings the message to the brain. The brain understands the message as a type of sound.

The Sound Barrier.The sound barrier is a speed barrier that judges an airplane’s

actions by the speed its going. To break the sound barrier you have to travel faster than the speed of sound. The shock wave that is made by an airplane moving at a supersonic speed makes a shocking change in air pressure.

The fastest plane ever is the SR-7I blackbird. Going through the sound barrier is very difficult because the

high-speed flight makes heat through friction. (eg. Rub your hands together really hard you will feel that they

are getting hotter. That is friction) Because of that, the surface of the plane’s temperature gets

higher then the safety limit for the structure of the aircraft.

Concorde was the only passenger plane to go faster than the speed of sound

Silent Space!

• In space, there are no solids, gases or liquids to travel through meaning sound can’t exist.

• Spacemen use radios to communicate with each other in space.

• So “In space no one can hear you scream”.

How Sound Travels • Sound is actually moving waves of molecules

and that molecules are found in matter. So how do different types of matter influence how sound travels?

• The medium has a direct effect on how fast sound travels. If the molecules that make up the substance are loosely packed, sound will travel slowly.

• If the molecules are tightly packed, sound will travel faster.

• Where there is no medium, no sound can be transmitted. Other factors that may affect the transmission of sound include temperature, humidity, and altitude.

Sound: High & Low

• Have you ever played a piano? Keys to the right side of a piano keyboard play notes that are higher than keys to the left

• The term pitch is used to talk about the "highness" or "lowness" of a sound.

• We say that the notes to the right of a piano keyboard have a higher pitch than the ones on the left.

• The pitch of a sound is directly related to the frequency of the sound wave.

• Higher frequency means higher pitch. • Lower frequency sound waves create sounds with lower

pitch. • Changing the frequency of a sound wave changes the

pitch of the sound.

Understanding Sound

To understand sound, you first need to understand matter. Everything is made up of matter. Matter is the general term we use to describe the "stuff" that is all around us. "What makes up matter?" you ask . . . molecules.

Molecules are small particles that you cannot see with your naked eye that join together to form everything around you: the table you are leaning on, the chair you are sitting in, the computer screen you are looking at. All these objects are made up of molecules, thousands and thousands of molecules.

Molecules in Motion

• "What is Sound?" Sound is created when something vibrates back and forth. The vibration pushes into molecules and creates a wave of sound.

• The sound wave starts at whatever is making the sound (by vibrating) and travels all the way to your ears, where you hear it.

• Molecules are so small that it is difficult to actually see them.

• As the string of a guitat makes sound waves, the molecules themselves don't move very far - it is the wave that travels as the molecules bump into each other.

Bouncing Sound

When a sound wave meets an obstacle, a portion of the wave is reflected from the obstacle, and the other portion is transmitted through the obstacle. Hard obstacles like concrete reflect almost all the sound, while soft materials like cloth allow the sound to be transmitted.

Other Sound Facts • Sound waves eventually stop because all the energy in

the wave is used as the molecules in the medium move. • As sound travels, its energy is used up, causing it to

become less intense (softer) the farther it travels from its source.

Sound Vocabulary – A Wave• What is a Wave? Before we talk about sound waves, let's find out

a little more about waves that you already know something about . . . ocean waves! You can think of any kind of wave as energy in motion or energy moving from point to point.

• Crest: the highest point on the wave •

Trough: the lowest point on the wave •

Wavelength: the distance from one crest to the next crest •

Amplitude: the distance between a wave's crest and trough• • Frequency: the number of waves passing a point in a given amount

of time

The Voice