Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure, the corresponding wavelengths of sound waves range from 17 m to 17 mm. Sometimes speed and direction are combined as a velocity vector; wave number and direction are combined as a wave vector.
Price of a Stamp. The current price of a first class stamp is 47 cents. A domestic first class letter (1 oz.) is 47 cents. The price of each additional ounce is 21 cents. It will cost you 34 cents to send a domestic postcard.
Copyright (c) 2015 by David Wincelberg. Stamps 1.1: Android app of this page, Featured shareware product. The postage rate for mailing a regular first-class letter in the United States starting May 31, 2015 is $0.49 for the first ounce and $0.22 for additional ounces up to 3.5 ounces.After that, you must use the rate for large envelopes, called flats, which starts at $0.98 and also adds $0.22 for additional ounces.After 13 ounces, mail with stamps applied must be presented at a post-office counter.) The second table below shows the values when only first-ounce stamps are applied and how many ounces for letters and flats are covered by using only these stamps.