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 Dolphins 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