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.
The cost of a forever stamp is the current cost of a first class stamp. In January of 2013 that is 46 cents. It is valid for the first ounce of mail regardless of the actual price.hat is the current price of a US Postal Service stamp for a first-class letter? The current (Aug 2014) price of postage for a standard first-class letter is 49 cents. Check out the website of the United States Postal Service for a full rundown, including additional-ounce costs (see Related Links).