The Science of Sound

What Is Sound?
How do you hear sound?

What sounds do you hear right now?
What responses do you have to sounds? Why?
What Is Sound?
Sound is energy
caused by vibration
that creates waves.
Energy
• Energy is the ability to do work or move an object with force.
• Sound moves the air (or matter) around us.
• Sound occurs when an object is vibrated by force.
• Sound is a type of energy.
Vibration
For sound to be produced, an object (or matter) needs to be vibrated or
moved by a force.
Sound Waves
The initial force used to make a sound vibrates the matter, surrounding it
in a chain reaction and creating waves.
How Are Sounds Different from
Each Other?
Sounds can have different pitches,

frequencies, wavelengths, and amplitudes,
so they sound different to our ears.
Properties of Sound
peak
wavelength
amplitude
amplitude
trough
The Relationship Between Pitch,
Frequency, and Wavelength
Pitch is the highness or lowness of a sound.
Although the waves
Frequency is the number of peaks of waves in a specific time period. The
have different
more peaks in this time, the higher the pitch.
Wavelength is the distance between two peaks or two troughs of waves. A
amplitudes, their
--------
--------
higher-pitched sound has a shorter wavelength.
wavelength
High-pitched soundsishave
thehigh frequencies (more waves occurring in a
same.
given Therefore,
amount of time).
High-pitched sounds have shorter wavelengths.
they have
Low-pitched thehave
sounds same
low frequencies (a smaller number of waves
occurring in a given amount of time).
pitch.
Low-pitched sounds have longer wavelengths.
Volume
amplitude
------------------------------
• Volume is proportional to the amplitude of the sound wave. It is how
loud or soft a sound is.
• Amplitude is the measurement of wave displacement from its resting
position. It can be measured from rest to peak or from rest to trough.
• Lower amplitude, like the wave on the left, means lower volume.
• Higher amplitude, like the wave on the right, means higher volume.
Measurement of Sound: Volume
Sound volume is measured in bels.

We commonly measure sounds audible to
humans in decibels, dB (one-tenth of a bel).
Bels are named in honor of Alexander
Graham Bell, who is credited with the
invention of the telephone.
Measurement of Sound: Volume
Human ears can be damaged by

A whisper
Loud musicis is
about 20110
about decibels.
decibels.
sounds louder than 85 decibels.
Insulators and Amplifiers
Sometimes, it is helpful to insulate sounds or make them quieter.

In what situations would a sound insulator be helpful?
It is also sometimes helpful to amplify sounds or make them louder.
In what situations would an amplifier be helpful?
Measurement of Sound: Frequency
Sound frequency is measured in a unit called Hertz (Hz).

10 Hz means that 10 sound waves pass a given point in one second.
Humans can generally hear sounds between 20 and 20,000 Hz.
How We Hear Sound
The vibrations caused by the initial object being vibrated reach our
eardrums.
In conjunction with our nerves and brain, our eardrums let us know that
we hear a sound.
Animals’ Hearing
Elephants
Human
Some can
earsdetect
canand
dolphins detect
even lower
batsa can
range
frequencies
of frequencies
hear than humans
of
up20
to – 20,000
(from Hz.
120,000 14
Hz.Hz).
Ultrasound and Infrasound Waves
Ultrasound waves have frequencies too high for humans to hear and
shorter wavelengths than other sound waves.
Infrasound waves have frequencies too low for humans to hear.

Uses for Ultrasound and Infrasound Waves
Ultrasound waves can reflect more easily than other sound waves. They
are useful in:
non-destructive
medical testing of medical
imaging uses sonar
mechanical
equipment
Infrasound waves can record earthquakes that humans may not feel.
Sound Scientist
Leonardo Da Vinci is credited with discovering that sound travels in

waves.
Sound Scientist
Galileo Galilei discovered the relationship between frequency and pitch.

Turn and Talk
• Why is sound considered to be a type

of energy?
(Remember that energy is the ability to do work or use a force to move an object.)
• Model the movement of sound from a

source to a human’s eardrum.
Think About It
What is the relationship between pitch, frequency, and wavelength?
Compare the sounds of a jet

plane’s engines and a parakeet
chirping.
Use the words pitch, frequency,
wavelength, and volume in your
comparison.

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What Is Sound?

How do you hear sound?

Sounds can have different pitches,

Sound volume is measured in bels.

Human ears can be damaged by

Sometimes, it is helpful to insulate sounds or make them quieter.

Sound frequency is measured in a unit called Hertz (Hz).

Infrasound waves have frequencies too low for humans to hear.

Leonardo Da Vinci is credited with discovering that sound travels in

Galileo Galilei discovered the relationship between frequency and pitch.

• Why is sound considered to be a type

• Model the movement of sound from a

Compare the sounds of a jet

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