HUMAN HEARING AND
NATURE’S APPLICATIONS
Section 10.1 and 10.7
Key Terms

Echolocation
The Human Ear

Consists of the outer ear, the middle ear and the
inner ear.
How You Hear

Sound waves are longitudinal waves
 These
waves enter the auditory canal and cause the
tympanic membrane to vibrate
 Compressions
and rarefactions of the air
Bones in the Ear

The function of these bones is to magnify the
vibrations of the tympanic membrane and transfer
them to the inner ear.
 Malleus
 “Hammer”
 Incus
 “Anvil”
 Stapes
 “Stirrup”
The Cochlea

A snail-shaped organ ~ 3cm long.
 Vibrations
in the oval window cause pressure waves in
the fluid that fills the cochlea.
 Waves
pass over cilia
 Cilia convert pressure waves into electrochemical nervous
impulses that are sent to the brain

This is “Hearing”
10.1 Summary





The characteristics and properties of waves help explain natural
phenomena, such as how we hear.
The audible human hearing range is from 20 Hz to 20 kHz, but we
perceive sound in the frequency range of 1000 Hz to 5500 Hz more
than other frequencies.
The outer ear consists of the pinna and auditory canal. The pinna
gathers sound and channels it into the auditory canal toward the
middle ear.
The middle ear consists of the eardrum and three small bones: the
hammer, the anvil, and the stirrup. The eardrum vibrates when it
encounters sound waves, and the bones transmit and magnify the
vibrations.
The inner ear contains the cochlea and the auditory nerve. The
vibrations are transformed into electrical impulses in the cochlea. The
cochlea sends the impulses through the auditory nerve to the brain.
Echolocation

Using echoes to locate an object


Use a variety of frequencies (40 kHz – 130 kHz)
Dolphins


Nasal sacs to make high-frequency sounds.
Sounds pass through the “melon”




Oval-shaped sac that is filled with acoustical lipids that focus the
sound waves
Echo is received by a
fat-filled cavity in lower jaw
Only good for ~ 5m - 200m
(High frequency sound)
Vibrations are conducted to
an auditory nerve and are
perceived by dolphin much the
same as sound in humans.
Elephants



Extremely intelligent
Large portion of their brain devoted to hearing.
Large pinnae
 Used
mostly for cooling and
threat display


Have hearing receptors
in trunks and feet
Produce sound from
15Hz – 35Hz up to 117dB
 Long
distances
House Cats


Excellent hearing (from 55 Hz – 79 kHz)
Large, moveable pinnae
 Amplification

and directionality of sound.
Make up for poor
vision with their
excellent hearing.
 Seeing
well in the
dark sacrifices
some colour
vision
10.7 Summary





Natural phenomena can be explained with reference to the
characteristics and properties of sound waves.
Dolphins, sperm whales, and orca whales use echolocation to
navigate and detect prey in dark, murky waters.
Bats also use echolocation to detect prey.
Elephants produce infrasound waves, which travel partially
through the ground. They can detect these sounds with their
feet and trunks pressed against the ground.
Cats use their large movable pinnae to amplify sound and
to detect the direction from which sounds are coming.
Homework

Page 453
 Questions

1, 3, 4
Page 474
 Questions
2, 3