Notice that there are sounds which exceed the threshold
of pain. Exposure to these sounds can cause immediate damage to hearing.In fact, exposure to sounds from
80 dB and above can damage hearing over time. Measurescan be taken to avoid damage, such as wearing earplugs
or ear muffs.Limiting exposure time and
increasing distance between you and the source are alsoimportant steps for protecting your hearing.
Discussion : importance of safety equipment
Working in groups of 5, discuss the importance of safety equipment such as ear protectors for workers in loud environments, e.g. those who use jack hammers or direct aeroplanes to their parking bays. Write up your conclusions in a one page report. Some prior research into the importance of safety equipment might be necessary to complete this group discussion.
Summary
Sound waves are longitudinal waves
The
frequency of a sound is an indication of how high or low the
pitch of the sound is.
The human ear can hear frequencies from 20 to 20 000 Hz.
Infrasound waves have frequencies lower than 20 Hz.
Ultrasound waves have frequencies higher than 20 000 Hz.
The
amplitude of a sound determines its
loudness or volume.
The
tone is a measure of the
quality of a sound wave.
The speed of sound in air is around
. It is dependent on the temperature, height above sea level and the phase of the medium through which it is travelling.
Sound travels faster when the medium is hot.
Sound travels faster in a solid than a liquid and faster in a liquid than in a gas.
Sound travels faster at sea level where the air pressure is higher.
The intensity of a sound is the energy transmitted over a certain area. Intensity is a measure of frequency.
Ultrasound can be used to form pictures of things we cannot see, like unborn babies or tumors.
Echolocation is used by animals such as dolphins and bats to “see” their surroundings by using ultrasound.
Ships use sonar to determine how deep the ocean is or to locate shoals of fish.
Exercises
Choose a word from column B that best describes the concept in column A.
Column A
Column B
pitch of sound
amplitude
loudness of sound
frequency
quality of sound
speed
waveform
A tuning fork, a violin string and a loudspeaker are producing sounds. This is because they are all in a state of:
compression
rarefaction
rotation
tension
vibration
What would a drummer do to make the sound of a drum give a note of lower pitch?
hit the drum harder
hit the drum less hard
hit the drum near the edge
loosen the drum skin
tighten the drum skin
What is the approximate range of audible frequencies for a healthy human?
0.2 Hz
200 Hz
2 Hz
2 000 Hz
20 Hz
20 000 Hz
200 Hz
200 000 Hz
2 000 Hz
2 000 000 Hz
X and Y are different wave motions. In air, X travels much faster than Y but has a much shorter wavelength. Which types of wave motion could X and Y be?
X
Y
A
microwaves
red light
B
radio
infra red
C
red light
sound
D
sound
ultraviolet
E
ultraviolet
radio
Astronauts are in a spaceship orbiting the moon. They see an explosion on the surface of the moon. Why can they not hear the explosion?
explosions do not occur in space
sound cannot travel through a vacuum
sound is reflected away from the spaceship
sound travels too quickly in space to affect the ear drum
the spaceship would be moving at a supersonic speed
A man stands between two cliffs as shown in the diagram and claps his hands once.
Assuming that the velocity of sound is
, what will be the time interval between the two loudest echoes?
1 s
A dolphin emits an ultrasonic wave with frequency of 0,15 MHz. The speed of the ultrasonic wave in water is
. What is the wavelength of this wave in water?
0,1 mm
1 cm
10 cm
10 m
100 m
The amplitude and frequency of a sound wave are both increased. How are the loudness and pitch of the sound affected?
loudness
pitch
A
increased
raised
B
increased
unchanged
C
increased
lowered
D
decreased
raised
E
decreased
lowered
A jet fighter travels slower than the speed of sound. Its speed is said to be:
Mach 1
supersonic
subsonic
hypersonic
infrasonic
A sound wave is different from a light wave in that a sound wave is:
produced by a vibrating object and a light wave is not.
not capable of traveling through a vacuum.
not capable of diffracting and a light wave is.
capable of existing with a variety of frequencies and a light wave has a single frequency.
At the same temperature, sound waves have the fastest speed in:
rock
milk
oxygen
sand
Two sound waves are traveling through a container of nitrogen gas. The first wave has a wavelength of 1,5 m, while the second wave has a wavelength of 4,5 m. The velocity of the second wave must be:
the velocity of the first wave.
the velocity of the first wave.
the same as the velocity of the first wave.
three times larger than the velocity of the first wave.
nine times larger than the velocity of the first wave.
Sound travels at a speed of 340 m
s
. A straw is 0,25 m long. The standing wave set up in such a straw with one end closed has a wavelength of 1,0 m. The standing wave set up in such a straw with both ends open has a wavelength of 0,50 m.
calculate the frequency of the sound created when you blow across the straw with the bottom end closed.
calculate the frequency of the sound created when you blow across the straw with the bottom end open.
A lightning storm creates both lightning and thunder. You see the lightning almost immediately since light travels at
. After seeing the lightning, you count 5 s and then you hear the thunder. Calculate the distance to the location of the storm.
A person is yelling from a second story window to another person standing at the garden gate, 50 m away. If the speed of sound is 344 m
s
, how long does it take the sound to reach the person standing at the gate?
A piece of equipment has a warning label on it that says, "Caution! This instrument produces 140 decibels." What safety precaution should you take before you turn on the instrument?
What property of sound is a measure of the amount of energy carried by a sound wave?
Person 1 speaks to person 2. Explain how the sound is created by person 1 and how it is possible for person 2 to hear the conversation.
Sound cannot travel in space. Discuss what other modes of communication astronauts can use when they are outside the space shuttle?
An automatic focus camera uses an ultrasonic sound wave to focus on objects. The camera sends out sound waves which are reflected off distant objects and return to the camera. A sensor detects the time it takes for the waves to return and then determines the distance an object is from the camera. If a sound wave (speed = 344 m
s
) returns to the camera 0,150 s after leaving the camera, how far away is the object?
Calculate the frequency (in Hz) and wavelength of the annoying sound made by a mosquito when it beats its wings at the average rate of 600 wing beats per second. Assume the speed of the sound waves is 344 m
s
.
How does halving the frequency of a wave source affect the speed of the waves?
Humans can detect frequencies as high as 20 000 Hz. Assuming the speed of sound in air is 344 m
s
, calculate the wavelength of the sound corresponding to the upper range of audible hearing.
An elephant trumpets at 10 Hz. Assuming the speed of sound in air is 344 m
s
, calculate the wavelength of this infrasonic sound wave made by the elephant.
A ship sends a signal out to determine the depth of the ocean. The signal returns 2,5 seconds later. If sound travels at
1450 m.s
in sea water, how deep is the ocean at that point?
Questions & Answers
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?