P1.5.3 Sound Mr D Powell. Mr Powell 2012 Index Connection Connect your learning to the content of the lesson Share the process by which the learning will.

P1.5.3 Sound

P1 PHYSICSMr D Powell

Mr Powell 2012Index

Connection

• Connect your learning to the content of the lesson

• Share the process by which the learning will actually take place

• Explore the outcomes of the learning, emphasising why this will be beneficial for the learner

Demonstration

• Use formative feedback – Assessment for Learning

• Vary the groupings within the classroom for the purpose of learning – individual; pair; group/team; friendship; teacher selected; single sex; mixed sex

• Offer different ways for the students to demonstrate their understanding

• Allow the students to “show off” their learning

Activation

• Construct problem-solving challenges for the students

• Use a multi-sensory approach – VAK• Promote a language of learning to

enable the students to talk about their progress or obstacles to it

• Learning as an active process, so the students aren’t passive receptors

Consolidation

• Structure active reflection on the lesson content and the process of learning

• Seek transfer between “subjects”• Review the learning from this lesson and

preview the learning for the next• Promote ways in which the students will

remember• A “news broadcast” approach to learning

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Practical Investigation...

1. Take your ruler and investigate the sound wave it creates by “twanging” it with your fingers. (Take care not to break it)

2. Think about the relationship between pitch (frequency) and length.

3. Then make a verbal prediction for what might happen with a string or tube and draw a diagram.

4. Now test out and write down what you find.

Draw a circle in your book and write inside it to explain How a sound wave moves through the air? (1/3rd page)

P1.5.3 Sound

a) Sound waves are longitudinal waves and cause vibrations in a medium, which are detected as sound.

NB: Sound is limited to human hearing and no details of the structure of the ear are required.

b) The pitch of a sound is determined by its frequency and loudness by its amplitude.

c) Echoes are reflections of sounds.

P1.5.3 Sound

Mr Powell 2012Index

Explaining Soundwaves?Particles move at

90 to the direction of travel

Particles move in direction of the wave

Energy is transferred

The pattern is

regular

Particles move side to sideParticles undergo

rarefaction

Vibration is

perpendicular to

the direction of

travelParticles are

compressed

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How is Sound Produced... (watch the movie) – RECAP Y9

Trachea

The vocal folds, also known commonly as vocal cords, are composed of twin infolding of mucous membrane stretched horizontally across the larynx.

1. They vibrate, modulating the flow of air being expelled from the lungs.

2. Open during inhalation, closed when holding one's breath, and vibrating for speech or singing.

3. They oscillate 440 times per second when singing A (above middle C).

4. The folds are controlled via the vagus nerve.

5. They are white because of scant blood circulation.

TASK: Imagine you are a doctor talking to a patient. They have problems talking as their vagus nerve is damaged. You will need to explain the mechanics of speech so they understand you. Read the text to help you remember from medical school!

Larynx

Vocal cords

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How is Sound heard... (watch the movie) – RECAP Y9The outer ear collects sound (green). The sound is amplified through the middle ear (red) which is hollow, and filled with liquid, containing a sensory epithelium that is studded with hair cells.

The tiny "hairs" from the cells stick out into the fluid. The hair cells release a chemical neurotransmitter when stimulated. In this way sound waves are transformed into nerve impulses. (purple)

The nerve impulses travel to both sides of the brain with the vestibular nerve dealing with sensing balance.

The human ear can generally hear sounds with frequencies between 20 Hz and 20 kHz (the audio range).

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a/b) The Trumpet

Trumpet Chromatic Scale

Period ms Frequency Hz(Calculated)

Frequency Hz

Bb C 4 250 261B C# 277C D 293C# Eb 311D E 329Eb F 349E F# 3 333 370F G 392

F# Ab 415

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a/b) The Real World

However, the frequency of the harmonics in a real instrument may be twice, three times, four times or even more times the fundamental frequency.

All these frequencies together make up the note.

The bottom line here shows the wave pattern formed by the fundamental and harmonic frequencies when the note is played on the instrument.

A tuning fork produces a note with only one frequency. The shape of the wave on the oscilloscope is very smooth.

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a/b Real SoundsWe now know that we can convert our longitudinal sound wave to a transverse wave to show on a screen.

If we look at these three traces of a middle C note (261Hz) we can see they are all different but seem to have similar pattern in terms of frequency as.......

1 up and 1 down takes (1/261)th of a second or the length of an arrow!

You need to try an ignore the funny fluctuations, this is due to the timbre of the notes – or richness that some from the instrument itself due to the nature of the pipes or strings.

saxophone

violin

clarinet

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Sound Refraction

BASIC: Just as a submarine can use refraction to hide its acoustic signature from surface vessels, the same principle of sound refraction can be used to prevent certain observers from hearing the noise.

FURTHER: For example, an outdoor observer close to the ground will have sound waves refracted toward him when the ground is cooler than the ambient air and away from him when the ground is hotter than the air.

IN DEPTH: When the sun warms the Earth’s surface there is a temperature gradient. The speed of sound decreases as temperature decreases.

The sound wave fronts travel faster near the ground. This means that sound is refracted upwards away from listeners on the ground creating an “acoustic shadow” at you move away from the source.

This reverses when the ground is covered with snow or over a lake in the morning.

Underwater this speed depends on pressure (depth), temperature and salinity allowing submarines to hide in certain sections of water!

http://en.wikipedia.org/wiki/Sound_speed_gradient

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Mr Powell 2012Index

Mr Powell 2012Index

M4. • Q is louder• Q is higher (pitch/note but not frequency) [if loudness and pitch both mentioned but direction wrong / absent credit 1 mark]• louder because bigger amplitude/height • higher pitch because higher frequency/shorter wavelength/waves closer together• factor of 2 mentioned w.r.t either for each • for 1 mark

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Data Trends... (Extension)

Discuss this data with a partner. Can you see a trend in the numbers?

Can you comment on...

Gas -> Liquid -> Solid

the mass of the molecules or compounds? (as best you know)

Ethanol C2H5OHChloroform CHCl3

Glass SiO2

The bonding or strength of the structures

You can use the periodic table to help you? Think helium and voice box (fixed )

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Speed of Sound

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Speed of Sound

Now try out the experiment as shown. You will have have to be very accurate to make sure it works.

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Ultrasound Ranges....

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As a radiographer it is your task to make measurements of a foetus while it is in the womb. When you take a prenatal ultrasound scan, the echo of the pulse of ultrasound returns in 300 microseconds.

1. If the sound travels at a speed of 1500 m/s in the fluids of the womb, you can work out the depth of the tissue that is returning the echo.

2. Ultrasound equipment produces ultrasound with a frequency between 2MHz and 18 MHz. What are the wavelengths of ultrasound at these two frequencies?

3. Why does the radiographer not recommend X-rays as a method of viewing the foetus?

4. Why does she use ultrasound instead?

5. When the ultrasound enters the bladder, the wave changes direction, producing an image of the organ on the monitor. What causes this change in the direction of the wave?

Ultrasound – HT Questions

c=f so c/f =

=1540ms-1/2 x 106Hz = 7.7 x 10-4m or =1540ms-1/18 x 106Hz = 8.6 x 10-5m

c = 3 x 108 ms-1

1. 1500ms-1 x 150 x 10-6s = 0.225m

1540 m/s

http://en.wikipedia.org/wiki/Medical_ultrasonography