How We Hear 1958

Sound represents vibrational energy. It is created when a medium such as air, wood, metal, or a persons vocal cords vibrate. Sounds carried as energy are transferred from one molecule to the next in the vibrating medium. To understand sound, consider the analogy in which a stone is dropped into a body of water. This action produces ripples that will spread out in all directions from the point where the stone contacted the water. The ripples become weaker (decrease in intensity) as they get farther away from the origin. So it is with sound. The vibration through a medium proceeds in waves. However, unlike ripples on water, sound waves move away from their point of origin in three dimensions, not just two. Sound waves possess specific characteristics. Frequency represents the number of complete wave cycles per unit of time, usually one second. Frequency is expressed in hertz (Hz), which means cycles per second. Low-frequency sounds are those that vibrate only a few times per second, while high-frequency sounds vibrate many more times per second. The term used to distinguish your perception of higher-frequency sounds from lower-frequency sounds is pitch. The human ear responds to frequencies in the range of 20 Hz to 20,000 Hz (20 kHz), although most speech frequencies lie between 100 and 4,000 Hz. In the work environment, employers are obligated to protect their workers from hazardous noise. Hearing-conservation programs, when implemented effectively, are associated with increased worker productivity and decreased absenteeism. They also lead to fewer workplace injuries and workmans compensation claims. For more information on hearing, go to
http://science.education.nih.gov/supplements/nih3/hearing/guide/info-hearing.htm . This is clipped from the 1958 film, Gateways to the Mind, made for AT&T by the Warner Brothers Studio. The entire film is available at the Internet Archives.

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Education

Tags:

• Noise
• hearing
• sound
• loss
• decibels
• level
• NIOSH
• OSHA
• dB
• industrial
• hygiene
• ear
• conservation