Headphones let a single user listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air for anyone nearby to hear. Headphones are also known as earspeakers, earphones or, colloquially, cans. Circumaural and supra-aural headphones use a band over the top of the head to hold the speakers in place. The other type, known as earbuds or earpieces consist of individual units that plug into the user's ear canal. In the context of telecommunication, a headset is a combination of headphone and microphone.
Osmium is usually sold as a minimum 99.9% pure powder. Like other precious metals, it is measured by troy weight and by grams. Its price in 2012 was about $400 per troy ounce (or about $13,000 per kilogram), depending on the quantity and its supplier.
This page lists silver prices (live) showing prices per troy ounce, per sterling ounce, and 90% Coin Silver (also known as Junk Silver). Silver Troy Oz Price ($17.18) The troy ounce is the standard silver price that you see on the t.v. 1 troy ounce = 31.1034768 grams or 1.09714 U.S. Ounces.