Human Hearing and Nature’s Applications - PowerPoint Presentation

Slide1

Human Hearing and Nature’s Applications

Section 10.1 and 10.7Slide2

For a prize?

What does SONAR stand for?

SOund

NAvigation

and RangingSlide3

Echolocation

Using echoes to locate an object

Use a variety of frequencies (40 kHz – 130 kHz)

Dolphins

Nasal

sacs make high-frequency sounds.Sounds pass through the “melon”Oval-shaped sac that is filled with acoustical lipids that focus the sound wavesEcho is received by a fat-filled cavity in lower jawOnly good for ~ 5m - 200m (High frequency sound)Vibrations are conducted to an auditory nerve and are perceived by dolphin much thesame as sound in humans.videoSlide4

Elephants

Extremely intelligent

Large portion of their brain devoted to hearing.

Large pinnae

Used mostly for cooling and

threat displayHave hearing receptorsin trunks and feetProduce sound from15Hz – 35Hz up to 117dBLong distancesvideoSlide5

Bats

Of the some 900 species of bats, more than half rely on echolocation to detect obstacles in flight, find their way into roosts and forage for food.

Most bats produce echolocation sounds by contracting their larynx (voice box).

A

few species, though, click their tongues. Slide6

sounds are generally emitted through the mouth, but Horseshoe bats

(

Rhinolophidae

)

and Old World leaf-nosed bats

(Hipposideridae) emit their echolocation calls through their nostrils: there they have basal fleshy horseshoe or leaf-like structures that are well-adapted to function as megaphones. Slide7

calls are usually ultrasonic--ranging in frequency from 20 to 200 kilohertz (

kHz)

human hearing

normally tops out at around 20 kHz

.

In general, echolocation calls are characterized by their frequency; their intensity in decibels (dB); and their duration in milliseconds (ms). Video – what does this sound like? Slide8

pitch

bats

produce echolocation calls with both constant frequencies (CF calls) and varying frequencies that are frequently modulated (FM calls).

Most

bats produce a complicated sequence of calls, combining CF and FM components.

Although low frequency sound travels further than high-frequency sound, calls at higher frequencies give the bats more detailed information--such as size, range, position, speed and direction of a prey's flight. Slide9

bats emit calls as low as 50 dB and as high as 120 dB, which is louder than a smoke detector 10 centimeters from your ear.

That's

not just loud, but damaging to human hearing. The Little brown bat

(

Myotis

lucifugus) can emit such an intense sound. The good news is that because this call has an ultrasonic frequency, we are unable to hear it. Slide10

Too cool!

The ears and brain cells in bats are especially tuned to the frequencies of the sounds they emit and the echoes that result. A concentration of receptor cells in their inner ear makes bats extremely sensitive to frequency changes: Some Horseshoe bats can detect differences as slight as .000l

Khz

. For bats to listen to the echoes of their original emissions and not be temporarily deafened by the intensity of their own calls, the middle ear muscle (called the

stapedius

) contracts to separate the three bones there--the malleus, incus and stapes, or hammer, anvil and stirrup--and reduce the hearing sensitivity. This contraction occurs about 6 ms before the larynx muscles (called the crycothyroid) begin to contract. The middle ear muscle relaxes 2 to 8 ms later. At this point, the ear is ready to receive the echo of an insect one meter away, which takes only 6 ms. Slide11

Owls

An Owl's range of audible sounds is not unlike that of humans, but an Owl's hearing is much more acute at certain frequencies enabling it to hear even the slightest movement of their prey in leaves or undergrowth.Slide12

Some

owl

species have asymmetrically set ear openings (i.e. one ear is higher than the other) - in particular the strictly nocturnal species, such as the Barn Owl or the

Tengmalm's

(Boreal) Owl.

These species have a very pronounced facial disc, which acts like a "radar dish", guiding sounds into the ear openings. The shape of the disc can be altered at will, using special facial muscles! Slide13

Barn owlSlide14

Boreal OwlSlide15

Also, an Owl's bill is pointed downward, increasing the surface area over which the

soundwaves

are collected by the facial disc. In 4 species (Ural, Great Gray, Boreal/

Tengmalm's

& Saw-whet), the ear asymmetry is actually in the temporal parts of the skull, giving it a "lop-sided" appearance.Slide16

Northern Saw-whet OwlSlide17

Great gray owl skullSlide18

Owls listen for

prey movements through ground cover such as leaves, foliage, or even snow.

When

a noise is heard, the Owl is able to tell its direction because of the minute time difference in which the sound is perceived in the left and right ear - for example, if the sound was to the left of the Owl, the left ear would hear it before the right ear.

The

Owl then turns its head so the sound arrives at both ears simultaneously - then it knows the prey is right in front of it. Owls can detect a left/right time difference of about 0.00003 seconds (30 millionths of a second!)Slide19

House Cats

Excellent hearing (from 55 Hz – 79 kHz)

Large, moveable pinnae

Amplification and directionality of sound.

Make up for poor

vision with theirexcellent hearing.Seeing well in thedark sacrificessome colourvisionSlide20

On the offense?

hard

to believe that animals can in fact use auditory signals to harm other animals.

The bottlenose dolphin uses echolocation

frequencies

that can be over ten times our upper hearing of 20 kHz. Some high-intensity click sounds (230 dB) by bottlenose dolphins, beaked whales, and sperm whales may serve to debilitate prey by overloading fish lateral lines, ears, or shattering bony ossicles and other tissue. Slide21

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.