Intermediate 1 Physics

1
Intermediate 1 Physics

• Sound and Music

• Sound Waves

• Speed of Sound

• Using Sound

• Amplified Sound

2
Intermediate 1 Physics

• Sound and Music

Sound Waves
3
Sound Waves

• Vibrations
• Musical instruments produce sound when part of
  the instrument v _ _ _ _ _ _ _
• A guitar string vibrates when it is plucked.

vibrates.
4
Vibrations

• A trumpet blasts out sound when the a _ _
  inside it vibrates
• Energy is transferred from the vibrating object
  to the listener by sound w _ _ _ _ which
  travel through the air. These sound waves make
  the air v _ _ _ _ _ _ .

air
waves
vibrate.
5
Frequency

• Each note or sound has a frequency which is
  measured in h _ _ _ _ (Hz).
• A tuning f _ _ _ has the frequency
  engraved on it.
• This vibrating fork will produce 256 vibrations
  every s _ _ _ _ _ .
• This means that 256 sound w _ _ _ _ are
  produced in one second.

hertz
fork
second.
waves
6
Frequency

• F _ _ _ _ _ _ _ _
• number of waves produced in one second.

Frequency
7
Frequency

• A whistle produces a h _ _ _ _ _
  frequency sound than a vibrating drum.
• The whistle has a much higher p _ _ _ _ .

higher
pitch
The higher the pitch means the higher the f _
_ _ _ _ _ _ _
frequency
8
Detecting Sound

• S _ _ _ _ can be taken in by a microphone
  and a trace displayed on an oscilloscope.

Sound
9
Loud and quiet

• A loud sound transfers more e _ _ _ _ _
  so the oscilloscope trace will have a l _ _ _
  _ amplitude. The amplitude of a wave is the
  distance from the m _ _ _ _ _ of the wave
  to the top or bottom of the wave.

energy
large
middle
10
Loud and quiet
11
Loud and quiet

• A soft/quiet sound transfers l _ _ _
  energy so the oscilloscope trace will have a s _
  _ _ _ amplitude

less
small
12
High and Low Frequency

• The effect of changing the frequency of a note
  can be seen on the oscilloscope screen.

Sound _ has a higher frequency than sound _
.
B
A
13
High and Low Frequency

• If the frequency is doubled, we say that sound B
  is an o _ _ _ _ _ higher than sound A.

octave
frequency 256 512 1024 (Hz) one
octave t _ _ octaves
two
14
Changing the Note

• A musician tunes a guitar by making the string
  t _ _ _ _ _ _ or looser.
• While playing the guitar, the note is changed by
  altering the l _ _ _ _ _ of string which
  vibrates.

tighter
length
15
Changing the Note

• S _ _ _ _ strings produce a higher
  frequency than long strings.
• T _ _ _ _ strings produce a higher
  frequency than slack strings.

Short
Tight
16
Changing the Note

• An organ produces a variety of musical notes
  which depend on the l _ _ _ _ _ of the air
  column which vibrates. The shorter pipes have the
  shorter air columns which produce the h _ _ _
  _ _ frequency notes.

length
higher
17
Intermediate 1 Physics

• Sound and Music

Speed of Sound
18
Speed of Sound

• During a thunderstorm, the lightning flash is
  seen a short time b _ _ _ _ _ the roll
  of thunder is heard. This is due to the fact that
  l _ _ _ _ travels much faster than sound
  through the air.
•  

between
light
In air Speed of light 300 000 000 m/s Speed
of sound 340 m/s  
19
Calculating the Speed of Sound

• In a laboratory the speed of sound can be
  calculated using the formula below.

(meaning speed equals distance d _ _ _ _
_ _ by time)
divided
20
Speed of Sound Apparatus
different
21
Speed of Sound

• A loud sound is made. As the sound reaches
  microphone A, the timer s _ _ _ _ _ .
• When the sound waves reach microphone B, the
  timer s _ _ _ _ . The distance between the
  microphones is measured with a m _ _ _ _
  stick.
• The experiment can be r _ _ _ _ _ _ _
  to calculate a more accurate, average result.

starts
stops
metre
repeated
22
Speed of Sound

• Example
• Recorded times 0.0030 s, 0.0029 s, 0.0031 s,
  0.0027 s, 0.0029 s
• Average time 0.0146/5 s

0.0029
Distance travelled 1 metre
Speed distance/time 1.0/0.0029
m/s
344.8
23
Intermediate 1 Physics

• Sound and Music

Using Sound
24
Using Sound

• Sound can travel through s _ _ _ _ _ ,
  liquids and g _ _ _ _ .

solids,
gases.
The only thing that sound cannot pass through is
a v _ _ _ _ _ .
vacuum.
A vacuum is an e _ _ _ _ space, so there
are no particles to pass on the vibrations.
empty
25
Using Sound

• When listening to music, you hear
• s _ _ _ _ _ with a wide range of
  frequencies. We can detect sounds that range from
  about 20 hertz to
• 20 000 hertz. As we get o _ _ _ _ , the
  upper limit gradually falls to about 15 000 hertz.

sounds
older
Some animals can detect higher frequency sounds
than h _ _ _ _ _ .
humans.
26
Using Sound - Ultrasound

• Sound beyond the u _ _ _ _ limit of human
  hearing (20 000 Hz) is called ultrasound.
• Ultrasound can be used in hospitals to scan the
  b _ _ _ in the mother's womb.
• This can be used by a computer to produce an i
  _ _ _ _ of the baby on a screen.

upper
baby
image
27
Using Sound - Ultrasound

• A system called s _ _ _ _ is used by
  fisherman at sea.
• The ultrasound signal is transmitted towards the
  sea bed and an e _ _ _ is detected.
• Shoals of f _ _ _ are located by this
  method.

sonar
echo
fish
28
Sound Levels

• The sound level of a noise means how l_ _ _
  it is.
• The sound level varies depending on the source of
  the sound.

loud
Sound level is measured in d _ _ _ _ _ _
_ (dB).
decibels
29
Sound Levels

• 130 J _ _ engine at 50 metres
• 100 Pneumatic d _ _ _ _
• 70 Rush hour t _ _ _ _ _ _
• 0 S _ _ _ _ _ _

Jet
drill
Sound l _ _ _ _ (dB)
traffic
level
Silence
30
Sound Levels

• When sound levels rise to unacceptable levels,
  the problem is described as n _ _ _ _
  pollution.
• There are many sources of noise pollution, such
  as aircraft noise or pneumatic drills. Exposure
  to high sound levels over a long time can d _
  _ _ _ _
• our hearing. Listening through stereo headphones
  will produce a harmful effect if the v _ _ _
  _ _ is turned to maximum.

noise
damage
volume
31
Intermediate 1 Physics

• Sound and Music

Amplified Sound
32
Amplified Sound

• A stereo system can be used to l _ _ _ _ _
  to a compact disc (CD) or a radio programme. No
  matter what function is selected, the signal
  passes through an amplifier which turns a small
  amplitude electrical s _ _ _ _ _ into a
  higher amplitude one.

listen
signal
33
Amplified Sound

• Only the amplitude of the signal is changed. The
  frequency does n _ _ change.

not
When announcements are made at airports and
stations, the message has to be changed from
sound into e _ _ _ _ _ _ _ _ _
signals and back to sound.
electrical
34
Amplified Sound
When announcements are made at airports and
stations, the message has to be changed from
sound into e _ _ _ _ _ _ _ _ _
signals and back to sound.
electrical

• An electronic system of 3 parts is used to
  amplify the
• s _ _ _ _ given out by the announcer

signal
35
Amplified Sound
microphone
electrical
amplifier
stronger
loudspeaker
sound
36
Voltage Gain

• The performances of different amplifiers can be
  compared by finding the gain of the amplifier.

37
Voltage Gain

• Example
• Find the voltage gain of the following amplifier.

38
Voltage Gain

• 400

N.B. Voltage gain is just a number. It has no
u _ _ _ .
unit
39
Playback

• A recording of your own v _ _ _ _ will
  sound a bit strange when it is played back from a
  cassette.
• This is because we normally hear our own voice
  by
• vibrations of bones in our s _ _ _ _ and
• vibrations in the air being detected by our e _
  _ _
• When we listen to a recording of our own voice we
  hear it by
• vibrations in the a _ _ being detected by
  our ears only.
•  

voice
skull
ears
air
40
Playback

• A CD (compact disc) is a source of h _ _ _
  quality sound. As the CD spins inside the CD
  player, light from a l _ _ _ _ reflects
  off the CD. There is no wear and tear of the disc
  surface and there is very little background n
  _ _ _ _ .

high
laser
noise.
41
Intermediate 1 Physics

• Sound and Music

End of Unit