A public address system (PA system) is a sound amplification system used to allow a person or persons to address an audience at a greater volume than would be possible or practicable without such a system.
 At a minimum, such a system comprises a microphone, an amplifier and a loudspeaker.
 Examples of content include announcements and other audio material at sports stadiums, air and rail terminals, and the sound produced by a singer, musician or musical ensemble, as well as recorded music.
 A PA system may include multiple microphones and/or other sound sources, a mixing console to combine and modify multiple sources, and multiple amplifiers and loudspeakers for louder volume, greater coverage and/or wider distribution, such as that required to provide sound throughout an entertainment venue, an office building or retail space, or an outdoor environment.
A sabot (UK and Int.: , ), (US: ) is a structural device used in firearm or cannon ammunition to keep a sub-caliber flight projectile, such as a relatively small bullet or arrow-type projectile, in the center of the barrel when fired, if the bullet has a significantly smaller diameter than the bore diameter of the weapon used.
 The sabot component in projectile design is more than simply the relatively thin, tough and deformable seal known as a driving band or obturation ring needed to trap propellant gases behind a projectile, and also keep the projectile centered in the barrel, when the outer shell of the projectile is only slightly smaller in diameter than the caliber of the barrel.
 Driving bands and obturators are used to seal these full-bore projectiles in the barrel because of manufacturing tolerances; there always exists some gap between the projectile outer diameter and the barrel inner diameter, usually a few thousandths of an inch; enough of a gap for high pressure gasses to slip by during firing.
 Driving bands and obturator rings are made from material that will deform and seal the barrel as the projectile is forced from the chamber into the barrel.
 Small caliber jacketed bullets do not normally employ driving bands or obturators because the jacket material, for example copper or gilding metal, is deformable enough to serve that function, and the bullet is made slightly larger than the barrel for that purpose, (see Full metal jacket bullet and driving band).
 Sabots certainly use driving bands and obturators, because the same manufacturing tolerance issues exist when sealing the saboted projectile in the barrel, but the sabot itself is a more substantial structural component of the in-bore projectile configuration (Drysdale 1978).
 Refer to the two APFSDS (Armor Piercing Fin Stabilized Discarding Sabot) pictures on the right to see the substantial material nature of a sabot to fill the bore diameter around the sub-caliber arrow-type flight projectile, compared to the very small gap sealed by a driving band or obturator to mitigate what is known classically as windage.
 More detailed cutaways of the internal structural complexity of advanced APFSDS saboted long rod penetrator projectiles can be found at reference 2.
Inflatable habitats or expandable habitats are pressurized structures capable of supporting life in outer space whose internal volume increases after launch.
 They have frequently been proposed for use in space applications to provide a greater volume of living space for a given mass.
A barrel is one of several units of volume applied in various contexts; there are dry barrels, fluid barrels (such as the UK beer barrel and US beer barrel), oil barrels and so on.
 For historical reasons the volumes of some barrel units are roughly double the volumes of others; volumes in common usage range from about 100 to .
 In many connections the term "drum" is used almost interchangeably with "barrel".
The costomediastinal recess is a potential space at the border of the mediastinal pleura and the costal pleura.
 It assists lung expansion during deep inspiration, although its role is not as significant as the costodiaphragmatic recess, which has a greater volume.
 The lung expands into the costomediastinal recess even during shallow inspiration.
 The costomediastinal recess is most obvious in the cardiac notch of the left lung.
The Goodyear Aircraft Company of Akron, Ohio built the M-class blimp for the US Navy as the follow-on to the K-class anti-submarine warfare blimp used during World War II.
 It was a significantly larger airship.
 Four airships, designated M-1 through M-4, were delivered in early 1944.
 Operations of K-ships in tropical regions had shown a need for a blimp with greater volume to offset the loss of lift due to high ambient temperatures.
A cavalier is a fortification which is built within a larger fortification, and which is higher than the rest of the work.
 It usually consists of a raised platform within a fort or bastion, so as to be able to fire over the main parapet without interfering with the fire of the latter.
 Through the use of cavaliers, a greater volume of fire can be obtained, but its great height also makes it an easy target for a besieger's guns.
A barrel, cask, or tun is a hollow cylindrical container, traditionally made of wooden staves bound by wooden or metal hoops.
 Traditionally, the barrel was a standard size of measure referring to a set capacity or weight of a given commodity.
 For example, in the UK a barrel of beer refers to a quantity of 36 impgal .
 Wine was shipped in barrels of 119 L .
The tierce (also "terse") is both an archaic volume unit of measure of goods and the name of the cask of that size.
 The most common definitions are either one-third of a pipe or forty-two gallons.
Vindö was a little boat yard on the Swedish west coast, situated between Orust and the mainland outside Uddevalla.
 The yard was best known for their fantastic small wooden boats in the 1960s, and converted to GRP material in 1965.
 First they updated the present range of Vindö 30, but the newcomer - the 35 ft long Vindö 50 made the little yard famous.
 The combination of GRP hull and fine quality teak and mahogany structures demanded for newer boats, and the 29 ft long Vindö 32 was launched in 1973.
 Shortly after came the 31 ft long Vindö 40 - best known for the reversed topsides of the hull.
 In 1982 came Vindö 45 - a 34 ft long boat with more modern lines - and a greater volume.
 This was shortly followed by the first of many bankruptcies, and the yard stopped production of new boats in 1990.

Question: Which has a greater volume a Tierce or a UK Barrel ?
Answer: The tierce