|MadSci Network: Engineering|
Hi Niket, That's a good question. Your resoning is good, sound is a form of energy that can be converted to other forms of energy, including electrical energy. The only problem with this particular application is the available power. This website lists the power available for given sound levels: http://en.wikipedia.org/wiki/Sound_power The table shows that loud speech can deliver about 0.001 Watts or 1 milliWatt of power. Normal speech is much less, on the order of 10 microWatts! This is the total available power. If we assume that you can capture all of it and you are able to efficiently convert all of it to electrical energy, you will be well below the operating power of a typical mobile phone. During operation, a typical mobile phone handset can radiate several watts of power. Most of the battery power goes to driving the transmitter and antenna, but some of it will be taken by analog and digital circuitry in the phone. At the end of the day, the sound power in speech can at best reduce the required operating power by 0.1% or so. It can't really charge the battery as more power is used than produced, but it could increase battery life *slightly*. In the real world where much less than 100% of the available sound power can be converted to electrical power, battery life would not be noticeably increased. If you had sound power levels on the order of a jack hammer or a machine gun, you might see a difference, but it is still a significant engineering challenge. I hope that answers your question. http://madhu.com - http://madhu.com/blog
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