Acoustics in the Real World
Acoustics can be found in many different places in our world. Listed below are some of the practical uses of acoustics that people have used.
SONAR
The earliest sonar imaging used sound reflected off of the surface of the ocean. By measuring the time between the transmission of the pulse and the receipt of the reflection and a few calculations, an image of the ocean bottom was created. The technology has since then improved and currently there are better methods of transmitting and receiving sonar as well as producing cleaner pictures.
ULTRASOUND
What most people think of when they hear the word ultrasound are actually obstetric ultrasound scans. This is when obstetricians use sound waves to "paint" a picture of the fetus. Currently, real-time scanners are used which create a moving picture of the fetus that can be displayed on a monitor screen. These machines use high frequency sound waves that are between 3.5 and 7.0 megahertz.
SOUND CANCELING SOUND
Wyle Laboratories in California developed the WAS 300, a loudspeaker capable of producing up to 165 dB of sound. This would be used to cancel the noise created by jets taking off of runways at airports. This giant loudspeaker is a larger version of the noise cancellation headsets handed out on the airplanes themselves. Microphones are set up where the "offending" noise is created. The signal is sent back to the loudspeakers which creates an out of phase sound which helps to cancel the sound created by the jets.
ARCHITECTURE
The way a room is built and shaped can greatly effect how sound is reflected and therefore effecting how it sounds. Different materials also effects the quality of sound. Some materials reflect sound too well while others hardly reflect at all. A combination of different angles, materials and surfaces will produce an almost perfect, echoless listening experience.