Question: Decibel and Jet, are what type of item?

Context articles: Sports memorabilia
Airbreathing jet engine
DBZ (meteorology)
Free response
Stock keeping unit
Jet (magazine)
Ladder match
High–low pricing
Turbofan
Decibel (magazine)

The term sports memorabilia usually refers to a souvenir, memento, keepsake or token of remembrance that is directly connected to a famous athlete, sporting event or personality.
 These items are generally collected by fans that find sentimental and/ or monetary value of the item(s).
 There is no set parameter regarding the amount of items, type of sport, or even the era that an item may reflect.
 A piece of certain kind may be considered a collectable item.
An airbreathing jet engine (or "ducted jet engine") is a jet engine propelled by a jet of hot exhaust gases formed from heated and expanded air that is drawn into the engine via a compressor, typically a centrifugal or axial type.
 They are typically gas turbine engines.
 The opposite of airbreathing jet engines are non-airbreathing jet engines, such as rocket engines, for example, which are propelled by a jet of hot gases created by the chemical reaction of two or more compounds internally.
 While the majority of the mass flow of an airbreathing jet engine is provided by air taken from outside of the engine and heated internally, using energy stored in the form of fuel, a rocket engine's fuel provides both the energy and the mass flow to create thrust.
dBZ stands for "decibel relative to Z".
 It is a logarithmic dimensionless technical unit used in radar, mostly in weather radar, to compare the equivalent reflectivity factor (Z) of a radar signal reflected off a remote object (in mm per m) to the return of a droplet of rain with a diameter of 1 mm (1 mm per m).
 It is proportional to the number of drops per unit volume and the sixth power of drops' diameter and is thus used to estimate the rain or snow intensity.
 With other variables analyzed from the radar returns it helps to determine the type of precipitation.
 Both the radar reflectivity factor and its logarithmic version are commonly referred to as "reflectivity" when the context is clear.
Free response, usually referred to as essay, is a type of question used in tests in education, workplace, and government.
 Most free response questions ask or require the test-taker to state a belief, opinion, or write a short essay and support it with facts, examples, or other evidence.
 However, few tests solely rely on these types of problems, and tend to work in conjunction with other types, such as multiple choice.
 Free response questions generally test more than straight knowledge and ask for a "big picture" type of response "(see example)".
 Also, they usually allow the taker to choose an area in which they are familiar.
 According to National Council on Measurement in Education, a free-response item is a test item in which the responders must create a response or product rather than choose a response from a set supplied with the item.
 A short-answer item, mathematics problem, and writing sample are examples.
In the field of inventory management, a stock keeping unit (SKU) ( , or ) is a distinct type of item for sale, such as a product or service, and all attributes associated with the item type that distinguish it from other item types.
 For a product, these attributes could include, but are not limited to, manufacturer, description, material, size, color, packaging, and warranty terms.
 When a business takes an inventory, it counts the quantity it has of each SKU.
Jet is a digital magazine.
 As an American weekly marketed toward African-American readers, it was founded in 1951 by John H. Johnson of the Johnson Publishing Company in Chicago, Illinois.
 Initially billed as "The Weekly Negro News Magazine", "Jet" is notable for its role in chronicling the Civil Rights Movement from its earliest years, including coverage of the Emmett Till murder, the Montgomery bus boycott, and Martin Luther King Jr.
A ladder match is a type of match in professional wrestling, most commonly one where an item (usually a title belt) is hung above the ring, and the winner is the contestant who climbs a ladder and retrieves the item.
 The ladder itself becomes a key feature of the match, as wrestlers will use the ladder as a weapon to strike the opponent(s), as a launching pad for acrobatic attacks, and frequently these matches include impressive falls from the top of the ladder.
 However, there were very few matches in which the hung item must be used in a special manner in order to win the match, such as striking the opponent with the item (see Bam Bam Bigelow Vs. Scott Hall taser match, where one must strike the opponent with the taser, regardless of who retrieved the taser first).
High–low pricing (or hi–low pricing) is a type of pricing strategy adopted by companies, usually small and medium-sized retail firms, where a firm charges a high price for an item and later when the item's popularity has passed, sell it to customers by giving discounts or through clearance sales.
 The basic type of customers for the firms adopting high–low price will not have a clear idea about what a product's price would typically be or must have a strong belief that "discount sales = low price" or they must have strong preference in purchasing the products sold in this type or by this certain firm.
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion.
 The word "turbofan" is a portmanteau of "turbine" and "fan": the "turbo" portion refers to a gas turbine engine which achieves mechanical energy from combustion, and the "fan", a ducted fan that uses the mechanical energy from the gas turbine to accelerate air rearwards.
 Thus, whereas all the air taken in by a turbojet passes through the turbine (through the combustion chamber), in a turbofan some of that air bypasses the turbine.
 A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of those contributing to the thrust.
 The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio.
 The engine produces thrust through a combination of these two portions working together; engines that use more jet thrust relative to fan thrust are known as "low-bypass turbofans", conversely those that have considerably more fan thrust than jet thrust are known as "high-bypass".
 Most commercial aviation jet engines in use today are of the high-bypass type, and most modern military fighter engines are low-bypass.
 Afterburners are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or turbojet engines.
Decibel is a monthly heavy metal magazine published by the Philadelphia-based Red Flag Media since October 2004.
 Its sections include Upfront, Features, Reviews, Guest Columns and the Decibel Hall of Fame.
 The magazine's tag-line is currently "Extremely Extreme" (previously "The New Noise"); the editor-in-chief is Albert Mudrian.