Transcript Chapter 24 –Sound

Chapter 24 –Sound
24.3 –Sound , Perception and
Music
pp. 590-597
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.
NOISE POLLUTION
• When noise reaches a level that causes
pain or damages the body it is called noise
pollution.
• Noise pollution can damage the inner ear,
causing permanent hearing loss.
• Noise pollution can contribute to
sleeplessness, high blood pressure and
stress.
WHITE NOISE
• This is an equal mixture of all frequencies
(like white light is a mixture of all colors).
• White noise machines are used to calm
people and help make them sleep.
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 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 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 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.
3 MAIN FAMILIES OF
INSTRUMENTS
• String instruments
• Wind instruments
• Percussion instruments
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.
WIND INSTRUMENTS
• 2 types of wind instruments:
–Woodwind
–Brass
WIND INSTRUMENTS
• How wind instruments produce
sound: a vibration is created at
one end of its air column, and
then the vibration creates
standing waves in the air column.
PERCUSSION
• How they make sounds: They
produce sound when they are struck
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.