Sound

In 1970 Congress passed the Occupational Safety and Health Act. The act created The Occupational Safety and Health Administration (OSHA). It granted OSHA the authority to adopt existing federal standards or national consensus standards. In 1968 the American Conference of Government Industrial Hygienists published employee threshold limit values (TLVs) for hazardous substances. In 1971, per the act, OSHA adopted these standards calling them Employee Permissible Exposure Limits (PELs)… More

Katy Payne, while working at the Washington Park Zoo in Portland Oregon, discovered that elephants communicated with one another via infrasound – sound below 20 hertz (Hz). The human hearing range lies somewhere between 20 Hz and 20,000 Hz. The elephants were communicating at frequency levels outside the range of human hearing… More

It has been written that sound bends due to differences in air temperature and acoustic shadows can form. Not much empirical data seems to exist to support this. Perhaps the experiment described above can provide data to support this. I hope that we will be able to do this experiment and share that data… More

In 864 A.D., the Mayans finished constructing an ancient basketball court in the city of Chichen Itza located in the Yucatan jungle. The game played in this court differed slightly from the basketball we are used to today. There were two teams of two to four players competing against each other. The objective was for one team to get the ball through the stone hoop attached to the wall. One basket or shot through won the whole game. The ball, the size of small soccer ball, just barely fit through the openings… More

Close your eyes for a moment and pretend you are picnicking, during the mid-afternoon, with family and friends in Central Park. About a two football fields away you can see a softball game. You can see the men and women cheering as ballplayers smack the ball and race around the bases. You see a player slide into home plate and you watch the umpire signal him out. You can see all this action, but you cannot hear it. Later that night as the temperature cools and other softball teams are playing under the lights you can see and hear everything clearly. Why is this so? More

What is a sound wave? Not being able to see a sound wave makes this a difficult question. Close your eyes and picture dropping a hammer onto a table. As the hammer hits the table, you hear a loud noise. What happened? The hammer hitting the table created a disturbance in the medium causing a wave to propagate through the medium. What does that exactly mean? Here we are dealing with two independent events: first, the hammer hitting the table causing a disturbance; second, the wave propagating or moving away from the disturbance… More

Pretend for moment that you are riding a sound wave just emitted from oil refinery compressor. You are traveling on a wave in the air at atmospheric pressure and you slam into an acoustic wall consisting of fiberglass, recycled tires, and mass loaded vinyl. Picture what it would be like…More