Image of a Photocell. In size comparison, it is about 5x2mm. When the reflected laser beam meets the photocell, the beam can be transferred into an audio signal (37).
Within the video is an interview and demonstration of the laser microphone by Martin Simon, a laser specialist working at UCLA (39).
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A laser microphone is the last microphone that we will study in this series. This microphone functions through capturing vibrations off of a plane of some sort, like a window, for example. When a sound hits the window, such as someone talking from inside the room that the window is apart of, the window actually bends a little (34). By pointing the laser of a laser microphone at the window, the sound vibrations that cause the window to bend, also cause the laser beam to bend. The reflection of the laser beam is converted into an audio signal using a photocell (35); the photocell, a very tiny item, has to be placed in the spot where the laser beams reflection lands to receive the audio signal.
Laser microphones are mainly used for spying with laser microphone surveillance having started during the Cold War between the Soviets and Americans. It has also has been credited as a tools used to find Osama Bin Laden in 2011 (36). Laser microphone technology has increased the abilities of government surveillance, by them now being able to listen into conversations from outside of buildings. This accessibility to spying is something that has seen positive public opinion, such as the capture of Bin Laden, and negative opinions, such as causing American and British citizens to be openly worried about their own privacy. If interested, it appears that it is relatively easy to build a DIY laser microphone. |
Conclusion
As evidenced by the different pages of this section, there are multiple types of microphones - Many, many more than could be described here. This site serves as a general list of the most common variations of microphones. As seen, each microphone has its own processes and societal impacts, distinguishing each from the rest while they all still achieve the common goal of emitting sound.
34. Ralph P. Muscatell, Laser Microphone, U.S. Patent 4479265 A, filed November 26, 1982 and issued October 23, 1984. https://www.google.com/patents/US4479265.
35. Ralph P. Muscatell, Laser Microphone, U.S. Patent 4479265 A, filed November 26, 1982 and issued October 23, 1984. https://www.google.com/patents/US4479265.
36. Charles Arthur, “Laser Spying: is it Really Practical?,” The Guardian, August 22, 2013, http://www.theguardian.com/world/2013/aug/22/gchq-warned-laser-spying-guardian-offices.
37. General Purpose Photocell, Extra Parts, http://extra-parts.com/index.php?main_page=product_info&cPath=16&products_id=930&zenid=5a8f5e2583abeaf9d4018191c041bfbf.
39. CIA Laser Listener from YouTube accessed March 20, 2015.
35. Ralph P. Muscatell, Laser Microphone, U.S. Patent 4479265 A, filed November 26, 1982 and issued October 23, 1984. https://www.google.com/patents/US4479265.
36. Charles Arthur, “Laser Spying: is it Really Practical?,” The Guardian, August 22, 2013, http://www.theguardian.com/world/2013/aug/22/gchq-warned-laser-spying-guardian-offices.
37. General Purpose Photocell, Extra Parts, http://extra-parts.com/index.php?main_page=product_info&cPath=16&products_id=930&zenid=5a8f5e2583abeaf9d4018191c041bfbf.
39. CIA Laser Listener from YouTube accessed March 20, 2015.