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Ultrasonic Waves Are Waves Above 20000Hz Infrasonic Waves Most Bat and Dog Communication Is Ultrasonic While Elephants and Whales Are Infrasonic

Sound is a wave that propagates through air and other materials. The document discusses the basics of sound waves including wavelength, period, amplitude, frequency and pitch. It also explains the Doppler effect which is a change in frequency or pitch heard by an observer due to relative motion between the source of sound and the observer.

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Syamira Zakaria
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96 views4 pages

Ultrasonic Waves Are Waves Above 20000Hz Infrasonic Waves Most Bat and Dog Communication Is Ultrasonic While Elephants and Whales Are Infrasonic

Sound is a wave that propagates through air and other materials. The document discusses the basics of sound waves including wavelength, period, amplitude, frequency and pitch. It also explains the Doppler effect which is a change in frequency or pitch heard by an observer due to relative motion between the source of sound and the observer.

Uploaded by

Syamira Zakaria
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
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THE BASICS OF SOUND

SOUND IS A WAVE PROPAGATING


THROUGH THE AIR

WAVELENGTH: The distance between any two successive


equivalent points on the wave.

PERIOD: The amount of time it takes for a wave to travel a


distance of one wavelength.

AMPLITUDE: The height of the wave


FREQUENCY: The number of cycles per second that pass a given
location.
Humans can hear sounds between 20Hz- 20000Hz

Ultrasonic waves are waves above 20000Hz; Infrasonic waves


are waves below 20Hz
Most bat and dog communication is ultrasonic while
elephants and whales are infrasonic

Frequency determines the pitch of a sound

PITCH: How the brain interprets the frequency of an emitted


sound.
The higher the frequency, the higher the pitch.

The lower the frequency, the lower the pitch


THE DOPPLER EFFECT

FIRST OF ALL...WHO IS DOPPLER?!?

Christian Doppler
(1805-1853): An Austrian
physicist who conducted
experiments with
musicians on railway
trains playing
instruments as the train
approached them and
receded from them.

WHAT IS THE DOPPLER EFFECT?

A change in pitch, due to the relative motion between a source of


sound and the receiver.

One of the most common examples of is the change in


pitch that we hear as a car horn or siren on a vehicle
moves past us.
SOME USEFUL EQUATIONS

f = 1/T T= 1/ f; where f is measured in Hertz


T is measured in seconds

The speed of a wave is given by:


V=distance/time= /T = f

CASE #1: A MOVING SOURCE


f' = f

+ is used when the source is moving AWAY


from the observer

- is used when the source is moving TOWARDS the


observer

CASE #2: A MOVING OBSERVER

f ' = f {1vo/v}
- is used when the observer is moving TOWARDS
the source

+ is used when the observer is moving AWAY from


the source

APPLICATIONS
Radar Gun

Measure the speed at which a pitcher throws


Catch speeder
Track the motion of precipitation caused by storm clouds
Ultrasound

Measure the rate of blood flow in the arteries or the


heart.
Light

Red-shift-calculate galaxy speeds


As other galaxies move away from us, the light has a
lower frequency than if it were at rest.

PRACTICE PROBLEM

A train sounds as it approaches a tunnel in a cliff. The whistle


produces a tone of 650.0Hz, and the train travels with a speed of
21.2m/s.

a) Find the frequency heard by an observer standing near the


tunnel entrance.

b) The sound from the whistle reflects from the cliff back to the
engineer in the train. What frequency does the engineer hear?

Extra practice:
If the stationary observer hears a frequency of 700.0Hz what is the
speed of the train?

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