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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

how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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Sanket Reply
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Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
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I'm interested in nanotube
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Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
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I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
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Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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bamidele Reply
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Smarajit Reply
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