6.2 Echo Extended

Multiple Choice

When Mr. Sunshine yells his name in a cave, the sound reflects off the walls of the cave and travels back to his ears. What is this called?

• absorption

• echo

• frequency

• refraction

Multiple Choice

Ultrasound is a kind of sound wave with its frequency of more than ......

• 20 kHz

• 30 kHz

• 40 kHz

• 50 kHz

Multiple Choice

Dolphins warn each other of the presence of predator using ultrasound. We cannot hear the ultrasound because

• the sound is too low.

• human can only hear sound of frequency range from 20 Hz to 20 000 Hz.

• the sound was absorbed by water.

• the sound produce multiple echo until our ears cannot capture it.

Multiple Choice

Which of the following is used to listen to the heartbeat of a patient?

• Stethoscope

• Microphone

• Microscope

• Hearing aid

Multiple Choice

When do we hear echoes?

• When the emitted sound reaches the ear, the sound is reflected.

• When the emitted sound reaches the ear almost at the same time as the reflected sound.

• When the emitted sound reaches the ear before the reflected sound.

• All are correct

Multiple Choice

Which of the following objects is a good reflector of sound?

• Sweater

• Iron

• Sponge

• Sofa

Multiple Choice

Which of the following conclusions is correct?

• Good reflectors are objects with rough, rough surfaces.

• Poor reflectors are objects with smooth, hard surfaces.

• Objects that reflect sound well are large objects.

• Poor reflector of sound are soft, uneven objects.

Multiple Choice

A man stood 680 m from a cliff and shouted. How long after shouting does this person hear the echo back? Let the speed of sound in air be 340 m/s.

• 2s

• 1s

• 4s

• 6s

Multiple Choice

Which of the following is a good absorber of sound?

• Steel, wood, fabric

• Concrete, iron, cotton

• Stone, iron, steel

• Fabric, velvet, felt

Open Ended

Car's engine can make lots of noise and it may not be conducive for passengers and drivers. How do you think scientist has made the car to be as quiet as possible in the cabin to make the travelling journey better.

You may browse through in the internet to get more ideas.

Choose maximum of 3 aspects and explain them as much as you can.

SOUND CAN BE REFLECTED

Reflection of Sound

You can reflect a sound wave off something the same way light will reflect off a mirror or water waves will bounce off a sea wall and go back out to sea.

Stand some distance from a large flat wall and clap your hands repeatedly.

Almost immediately you'll hear a ghostly repeat of your clapping.


What you hear is, of course, sound reflection, better known as an ECHO

Word Cloud

Where/How do you think echo are being used thoroughly?

Reflection of sound

Sonar

Sonar (sound navigation and ranging) is a technology that uses acoustical waves to sense the location of objects in the ocean.

Reflection of sound
Calculation

Sonar Calculation

Multiple Choice

The total time for sound waves to return to a ship was 8 seconds after being released. What is the depth in meters?

Distance (Depth) = Velocity x (Total time/2)

Velocity of sound in water = 1500 m/s

• 12,000m

• 6000m

• 375m

• 187.5m

Multiple Choice

The total time for sound waves to return to a ship was 4.5 seconds after being released. What is the depth in meters?

Distance (Depth) = Velocity x (Total time/2)

Velocity of sound in water = 1500 m/s

• 6750m

• 333.33m

• 667m

• 3375m

Multiple Choice

If the depth of the ocean floor is 9000 meters, how long, in total time, does it take sound waves to return to the SONAR detector?

Distance (Depth) = Velocity x (Total time/2)

Velocity of sound in water = 1500 m/s

• 13,500,000sec

• 12sec

• 0.17sec

• 3sec

Multiple Choice

If the depth of the ocean floor is 12000 meters, how long, in total time, does it take sound waves to return to the SONAR detector?

Distance (Depth) = Velocity x (Total time/2)

Velocity of sound in water = 1500 m/s

• 16sec

• 8sec

• 18,000,000sec

• 36,000,000sec

Multiple Choice

The time for sound waves to return to a ship from just the bottom of the ocean was 1.25 seconds. What is the depth in meters?

Distance (Depth) = Velocity x (Total time/2)

Velocity of sound in water = 1500 m/s

• 937.5m

• 1875m

• 10050m

• 1200m

Multiple Choice

If the depth of the ocean floor is 7500 meters, how long does it take sound waves to reach the bottom of the ocean?

Distance (Depth) = Velocity x (Total time/2)

Velocity of sound in water = 1500 m/s

• 10sec

• 5sec

• 11,250,000sec

• 0.2sec

Multiple Choice

The speed of sound varies when the medium it passes through changes. For example, the speed of sound through air is 343 m/s. A boat mapping the seafloor near Greenland determines after a 12-second ping, the depth is 8100 meters. What is the speed of sound in this cold, icy water?

Distance (Depth) = Velocity x (Total time/2)

• 1875m/s

• 48,600m/s

• 675m/s

• 1350m/s

Multiple Choice

People often use the reflection of ultrasound to determine the depth of the sea. Assume the ship emits a sonar and picks up its reflection from the seabed after 1 second. Calculate the approximate depth of the seabed, knowing the speed of ultrasonic propagation in water is 1500 m/s.

Distance (Depth) = Velocity x (Total time/2)

• 1500m

• 750m

• 500m

• 1000m