Transcript Standard EPS Shell Presentation

SOUND 24.3
Chapter Twenty-Four: Sound
24.1 Properties of Sound
24.2 Sound Waves
24.3 Sound Perception and
Music
Chapter 24.3 Learning Goals
Explore how the brain makes
meaning of sounds.
 Describe how humans hear
sounds.
Explain the sound is used to
create music.
24.3 Sound perception and music
When you hear a
sound, the nerves in
your ear respond to
more than 15,000
different frequencies
at once.
The brain makes sense
of complex sound
because the ear
separates the sound
into different
frequencies.
24.3 Sound perception and music
A frequency spectrum shows the
amplitudes of different frequencies
present in a sound.
24.3 Sonograms
 More information is
found in a
sonogram which
combines three
sound variables:
1. frequency,
2. time, and
3. amplitude (loudness).
24.3 Sonograms
Which letter
represents a soft
sound lasting 5
seconds?
What is it’s
frequency?
24.3 How we hear sound
 The parts of the ear work together:
1.
2.
3.
When the eardrum
vibrates, three small
bones transmit the
vibrations to the cochlea.
The vibrations make
waves inside the cochlea,
which vibrates nerves in
the spiral.
Each part of the spiral is
sensitive to a different
frequency.
24.3 Sound protection
Listening to loud sounds
for a long time causes the
hairs on the nerves in the
cochlea to weaken or
break off resulting in
permanent damage.
24.3 Music
The pitch of a sound is how high or
low we hear its frequency.
Rhythm is a regular time pattern in a
series of sounds.
Music is a combination of sound and
rhythm that we find pleasant.
24.3 The musical scale
Most of the music you listen to is
created from a pattern of frequencies
called a musical scale.
24.3 Superposition
The superposition principle states that
when sound waves occur at the same time
they combine to make a complex wave.
When two frequencies of sound are not
exactly equal in value, the loudness of the
total sound seems to oscillate or beat.
24.3 Music and notes
Each frequency in the scale is called a note.
The C major musical scale that starts on the
note C (262 Hz).
24.3 Music and harmony
Harmony is the study of how sounds work
together to create effects desired by the
composer.
The tense, dramatic sound track of a horror
movie is a vital part of the audience’s
experience.
Harmony is based on the frequency
relationships of the musical scale.
24.3 Music and harmony
When we hear more than one
frequency of sound and the
combination sounds pleasant, we call
it consonance.
When the combination sounds
unsettling, we call it dissonance.
24.3 Making sounds
The human voice is complex
sound that starts in the
larynx, at the top of your
windpipe.
The sound is changed by
passing over by expandable
folds (vocal cords) and
through openings in the
throat and mouth.
24.3 Making sounds
For a guitar in standard
tuning, the heaviest string
has a natural frequency of
82 Hz and the lightest a
frequency of 330 Hz.
Tightening a string raises
its natural frequency and
loosening lowers it.
24.3 Harmonics and music
The same note sounds different when
played on different instruments.
Suppose you compare the note C (262 Hz)
played on a guitar and the same note
played on a piano.
The variation comes from the harmonics
in complex sound.
A single C note from a grand piano might
include 20 or more different harmonics.
24.3 Harmonics and music
A tuning fork is a
useful tool for tuning
an instrument
because it produces a
single frequency
Investigation 24C
Perceiving Sound
Key Question:
 What is sound and how do we hear it??
Hearing
Deafness is poorly
understood in general.
For instance, there is a
common
misconception that
deaf people live in a
world of silence. To
understand the nature
of deafness, first one
has to understand the
nature of hearing.