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Professor Quester Answers
Questions on Geothermal & Ocean Energy



Dear Dr. Q:
My friends and I are doing a report on sound energy, we would like to know if you could send us some information on sound energy, if so please do. Just random facts and neat little findings. We need to get information from an outside source, I thought you would be a good choice.

The Professor Answers:
Let's see. First, sound is a form of energy that travels from the source to our ears by the vibration of air molecules. For instance, the sound of your voice is changed into electrical energy and the electrical energy is changed back into sound. The energy is most sounds is small, for example, the sound energy of 200 pianos is equal to the electrical energy needed to light just one light bulb.

Sound travels in sound waves. They spread through the air like ripples in a pond after you have thrown in a pebble. So, each layer of air bumps into the next layer, carrying the sound to your ears.

Lightwaves can travel through space but sound waves cannot...there is no sound in space. Sounds waves need something to travel through and there is no air in space.

Sounds waves travel about 340 meters (about 1,020 feet) each second and sound travel slightly faster in hot air and slightly slower in cold air. Sound travels about four times faster through water than through air and about 15 times faster through steel than air.

The faster something vibrates, the higher the sound it makes. How high or low a sound is, is called its pitch. The number of vibrations per second is called the frequency of the sound and is measured in hertz (Hz). Now why is this interesting???

Well, some animals use sound to help them "see." Bats are able to find their prey at night and fly in the dark without bumping into things (called echo-location). They send out lots of very high-pitched squeaks, then listen to the echoes bouncing off things. The shorter the time between the squeak and the echo, the closer they are to the object. Bats can hear higher sounds than any other animals...up to 210,000 Hz. The highest sounds people can hear are around 20,000Hz. Sound with a very high frequency is called ultrasound.

The loudest animal in the world is the blue whale. It can make sounds as loud as 188dB ( that's decibels or loudness of a sound) , that can be picked up over 2,000 miles away. Compare this to someone shouting at 70 dB, whispering at 30dB or a jet airplane taking off at 120 dB. Noises louder than 130 dB are painful.

Not all animals hear sounds as you do. Grasshoppers "hear" with their legs, waving them in the air to tell where a sound is coming from. Snakes do not have ears so they cannot hear sounds through the air. They pick up low sounds from the ground. Fish hear through their bodies.

Ultrasound is used to test cracks in metal such as airplanes, or used to look inside a mother at a growing baby. The echoes are changed into electrical signals and built up into a picture.




Dear Dr. Q:
Just wanna ask what are the advantages of tidal energy? And also examples of usage of tidal energy now. Need info urgently.   (Uni, Secondary Level, Singapore)

The Professor Answers:
California has no electricity produced from tidal energy. Tidal energy, like many forms of alternative energy, have high capital costs and need for improved performance before it can become commercially available. There are several forms of this type of energy: tidal energy. ocean thermal energy conversion and wave energy conversion. Right now costs to produce tidal energy range from 11 cent kWh to 20 cents/kWh. California's research looks more at ocean wave energy rather than tidal.

Check these sites for more information on tidal energy. Good luck with your project.

http://bigbro.biophys.cornell. edu/~duesing/work/ba.html
http://wsi-www1.cso.uiuc.edu/courses/GEOL105a/
MODULES/lectures/resources/lect838737014.html

http://tidalelectric.com/projects/index.html
http://www.iesd.dmu.ac.uk/~slb/wctide.html



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