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Sensing vibration

If you are standing somewhere between the car and the point at which the vibrations are no longer significant, the air molecules in your ear canals willbegin to vibrate. This will stimulate nerves that lead from your ear to your brain. Your brain will interpret the stimulation as something that we refer to sound .

Therefore, when the tree falls, it causes the air molecules to vibrate. However, if there are no ear canals around, no nerves to be stimulated, and no brain to interpretthat stimulation, there is no sound.

Creating sound with a hammer

All we need to do to cause a person to experience sound is to cause the air molecules in that person's ear canals to vibrate at afrequency somewhere between 20 Hz (cycles per second) and 20,000 Hz, depending on the person's age. Usually as a person ages, the range defined bythose upper and lower limits decreases. Thus, a young person may "hear" the high-pitched whine of a power saw while an older person may not experience soundin that situation.

There are many ways that we can cause most humans to experience sound. One way for example, is to strike a bell with a hammer. Another way is to write aprogram to cause the diaphragm of a computer speaker to vibrate. That will be the topic of the next few modules in this course.

Creating sound with a computer

One way to create sound with a computer would be to hold it out and drop it on the floor. However, that is not what we intend to do. Instead, we intend towrite computer program that will cause the computer to create sound.

An object of a class

As you will learn in a future module, we can define a class and instantiate an object of that class for use in producing sound with a computer. When usedproperly in a program, that object will cause signed numeric values stored in an array to be converted to electrical current in the speakers attached to the computer.Positive values will cause the current to flow in one direction and negative values will cause the current to flow in the opposite direction.

Alternating positive and negative values

If we populate that array with alternating groups of positive and negative values, that will cause the current being delivered to the speakers toalternate, switching from one direction to the other. The level of the alternating currents will be roughly proportional to the magnitudes of thealternating positive and negative values. Given sufficient magnitude within a frequency range supported by the speakers, the alternating currents will causethe diaphragms of the speakers to vibrate or move back and forth. This, in turn, will cause the adjacent air molecules to vibrate, which may be sensed as soundby a person within hearing distance of the speakers.

Sine and cosine functions

Populating the array

There are many ways that we can write a program to populate the array with alternating groups of positive and negative numbers. One of the simplest ways is topopulate the array with scaled versions of the values produced by the static sin function or the static cos function of the Math class. The Math class is contained in the Java Standard Edition class library. A common name for a series of such values is sinusoid .

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?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
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
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
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
Krampah Reply
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.
Sahid Reply
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
Samuel Reply
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?
Joseph Reply
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
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
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?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, Accessible objected-oriented programming concepts for blind students using java. OpenStax CNX. Sep 01, 2014 Download for free at https://legacy.cnx.org/content/col11349/1.17
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