Ch - 12 (Sound) Flashcards
How are sound waves produced?
vibrating sources
What type of wave do sound waves travel in?
Longitudinal ( back and forth )
Can sound travel in vacuum?
No, it needs a medium and particles to pass through.
What are 2 things a longitudinal wave consists of?
Compression
Rarefaction
What is a compression?
A region of higher density (ex - molecules are bunched together)
What is a rarefaction?
A region of lower density (ex - molecules are spread further apart)
What other type of wave is sound considered due to the changes in pressure?
Pressure wave
How is sound transferred?
Sound particles are produced, energy is passes on through vibrations, and sound reaches our ears.
How is the pressure in compression and rarefaction?
- Compression (High pressure)
- Rarefaction (Low pressure)
What is the speed of sound in air?
330 - 350 m/s
What is the speed of sound in liquid?
1500 m/s
What is the speed of sound in solid?
5000 m/s
What are the different methods to measure speed of sound?
Method 1: Measuring sounds between 2 points
Method 2: Using echoes
Method 3: Using an oscilloscope
What is the apparatus required for (Method 1: Measuring sounds between 2 points)?
- Trundle wheel
- two wooden blocks
- stopwatch
Speed = d/t
What is the apparatus required for (Method 2: Using echoes)?
- Trundle wheel
- 2 wooden blocks
- stopwatch
Speed = 2 x d / t
What is the apparatus required for (Method 3: Using an oscilloscope)?
- Microphone
- oscilloscope
- tape measure
Speed = d between microphones / time between peaks
Which of the three methods are most accurate?
Method 1: Measuring sounds between 2 points
Method 2: Using echoes
Method 3: Using an oscilloscope
Method 3 because timing is done automatically.
which of the three methods is the least accurate?
Method 1: Measuring sounds between 2 points
Method 2: Using echoes
Method 3: Using an oscilloscope
Method 1 because the time intervals are very short
What is the method to measure wave speed in water?
By creating ripples in water
Apparatus:
- Tape measure
- stopwatch
Procedure:
- disturb the water
- time how long it takes for the First ripple to reach the other person
Speed = distance travelled / time taken
What part of the wave determines the pitch?
Frequency
What part of the wave determines loudness?
Amplitude
What happens in High pitch and low pitch?
High pitch : High frequency
Low pitch : Low frequency
What happens in a loud and soft sound?
Loud : High amplitude
Soft : Low amplitude
What is an echo?
The reflection of a sound wave off a surface is called an echo
what can echoes be used to measure?
- Depth
- To detect objects underwater
What can echoes do to measure the depth?
- A sound wave can be transmitted from the surface of the water
- sound wave is reflected from the bottom
What measurements are used to measure the depth of the water?
the time it takes for sound waves to return
What measurement is used to measure the depth of the ocean?
The distance the wave travels is twice the depth of the ocean
What is the range that humans can hear up to?
20 - 20,000 Hz
Define ultrasound.
it is the name given to the sound wave with a frequency greater than 20,000 Hz
What happens when ultrasound reaches a boundary between 2 media?
Some of the waves are partially reflected.
The remainder of the wave is transmitted.
What are ultrasound transducers able to do?
- Emit ultrasound
- Recieve ultrasound
How can ultrasound be used to determine how far a boundary is?
because ultrasound travels at different speeds through different media.
What is the equation to use?
v = s / t
v = speed in metres per sec
s = distance in metres (m)
t = time taken in sec (s)
How is ultrasound used in medicine?
- construct images of the foetus
- to generate 2D images of organs and internal structures (that are not surrounded by a bone)
- medical treatment to remove kidney stones
What is an ultrasound detector made out of?
Transducer that produces a beam of ultrasound waves into the body.
What does the ultrasound detector do?
- Ultrasound waves are reflected back to the transducer by boundaries between tissues in the path of beam
- The echoes hit the transducer, they generate electrical signals, are sent to ultrasound scanners.
- the speed of sound and eco od each is measured and shown
What happens when you take a series of ultrasound?
The time measurements are used to build up an image.
What is different about ultrasound scanners?
It is non - invasive and harmless
How is ultrasoud used in the industry?
- Check for cracks inside metal objects
- generate images beneath the surface
How can the ultrasound be sued for a crack inside a metal ibject?,
- cause some waves to reflect earlier than rest, it will show up as pulses, on oscilloscope
- each pulse represents the time the wave crosses the boundary.
