Beath High School - Int 1 Physics 1

Intermediate 1 Physics

Sound and Music Sound Waves

Speed of Sound

Using Sound

Amplified Sound

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Intermediate 1 Physics

Sound and Music

Sound Waves

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Sound Waves

VibrationsMusical instruments produce sound when

part of the instrument v _ _ _ _ _ _ _

A guitar string vibrates when it is

plucked.

vibrates.

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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.

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FrequencyEach 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

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Frequency

F _ _ _ _ _ _ _ _

= number of waves produced in one second.

Frequency

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Frequency

A whistle produces a h _ _ _ _ _

frequency sound than a vibrating drum.

The whistle has a much higher p _ _ _ _ .

higher

The higher the pitch means the

higher the f _ _ _ _ _ _ _ _

pitch

frequency

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Detecting Sound

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

Sound

microphoneOscilloscope

tuningfork

sound waves travel from fork to microphone

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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

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Loud and quiet

Loud notehas largeamplitude

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A soft/quiet sound transfers l _ _ _

energy so the oscilloscope trace will

have a s _ _ _ _ amplitude

Loud and quiet

less

small

Quiet notehas smallamplitude

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

High and Low Frequency

Sound A has low frequency

Sound B has high frequency

Sound _ has a higher frequency than sound _ .

B

A

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frequency: 256 512 1024(Hz)one octavet _ _ octaves

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

High and Low Frequency

octave

two

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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.

Changing the Note

tighter

length

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S _ _ _ _ strings produce a higher frequency than long strings.

T _ _ _ _ strings produce a higher frequency than slack strings.

Changing the Note

Short

Tight

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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.

Changing the Note

length

higher

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Intermediate 1 Physics Sound and Music

Speed of

Sound

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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.

 

Speed of Sound

between

light

In air: Speed of light = 300 000 000 m/s Speed of sound = 340 m/s  

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(meaning; speed equals distance d _ _ _ _ _ _ by time)

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

Calculating the Speed of Sound

divided

timespeed =

distance

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Speed of Sound : Apparatus

differentmicrophone A

electronic timer

microphone BHammer

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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.

Speed of Sound

stops

starts

metre

repeated

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Speed = distance/time = 1.0/0.0029 = m/s

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

Speed of Sound

0.0029

344.8

Distance travelled = 1 metre

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Intermediate 1 Physics Sound and Music

Using Sound

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A vacuum is an e _ _ _ _ space, so there are no particles to pass on the vibrations.

The only thing that sound cannot pass through is a v _ _ _ _ _ .

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

solids,

Using Sound

gases.

vacuum.

empty

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Some animals can detect higher frequency sounds than h _ _ _ _ _ .

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

Using Sound

older

humans.

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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

Using Sound - Ultrasound

baby

image

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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

Using Sound - Ultrasound

echo

fish

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Sound level is measured in

d _ _ _ _ _ _ _ (dB).

The sound level of a noise means how l_ _ _ it is.

The sound level varies depending on the source of the sound.

loud

Sound Levels

decibels

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Sound l _ _ _ _ (dB)

130 J _ _ engine at 50 metres

100 Pneumatic d _ _ _ _

70 Rush hour t _ _ _ _ _ _

0 S _ _ _ _ _ _

level

Sound Levels

Jet

drill

traffic

Silence

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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

Sound Levels

damage

volume

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Intermediate 1 Physics Sound and Music

Amplified Sound

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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

Amplified Sound

signal

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When announcements are made at airports and

stations, the message has to be changed from sound

into

e _ _ _ _ _ _ _ _ _ signals and back to sound.

Only the amplitude of the signal is changed. The

frequency does n _ _ change.

Amplified Sound

not

electrical

Amplifier

small amplitude input signal large amplitude output signal

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When announcements are made at airports and stations, the message has to be changed from sound into

e _ _ _ _ _ _ _ _ _ signals and back to sound.An electronic system of 3 parts is used to amplify the

s _ _ _ _ given out by the announcer

Amplified Sound

electrical

soundsound withincreasedamplitude

Inputmicrophone

Process amplifier

Outputloudspeaker

signal

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Part of the system Function

m _ _ _ _ _ _ _ _ _converts sound into ane _ _ _ _ _ _ _ _ _ signal

a _ _ _ _ _ _ _ _makes the electrical

signal

s _ _ _ _ _ _ _ (bigger

amplitude)

l _ _ _ _ _ _ _ _ _ _converts the electrical signal back to s _ _ _ _

microphone

Amplified Sound

electrical

amplifier stronger

loudspeaker sound

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The performances of different amplifiers

can be compared by finding the gain of

the amplifier.

Voltage Gain

Voltage gain =0utput voltage

Input voltage

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Example:Find the voltage gain of the following amplifier.

Voltage Gain

input0.01V

output4V

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= 400

Voltage Gain

Voltage gain =0utput voltage

Input voltage

40.01=

N.B. Voltage gain is just a number.

It has no u _ _ _ .unit

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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 _ _ _ _ andvibrations 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.

 

Playback voice

skullears

air

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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

_ _ _ _ .

Playback

high

laser

noise.

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Intermediate 1 Physics Sound and Music

End of Unit