muffler

1. A heavy scarf worn around the neck for warmth.
2. A device that absorbs noise, especially one used with an internal-combustion engine.

A device used to attenuate sound while also allowing fluid (usually gas) to flow through it; also known as silencer in British usage. Mufflers are extensively used to reduce the intake and exhaust noise from pumps, fans, compressors, and internal combustion engines. Although active noise control techniques are emerging, most mufflers continue to use passive silencing methods. Passive mufflers are categorized as reactive or dissipative based on their primary method of attenuation. Reactive mufflers reflect sound back toward the noise source, and dissipative mufflers use porous materials to absorb the sound.

Reactive mufflers reflect acoustic waves at locations where a duct expands, contracts, or branches. Often a combination of reactive elements such as expansion chambers, resonators, and flow reversals is used. Reactive mufflers can be designed to provide better low-frequency attenuation than a dissipative muffler of similar size. Also, reactive mufflers can be used in harsh environments that dissipative or active mufflers might not withstand. In most cases, reactive mufflers are best suited for low-to-moderate frequencies, where acoustic wavelengths are larger than any cross dimension of the muffler. At these frequencies, mufflers can exhibit resonance or broadband attenuation behavior. See also Resonance (acoustics and mechanics).

Dissipative mufflers use absorptive materials that dissipate the acoustic energy into heat. A variety of porous media can be used for absorption, with fibrous materials such as fiberglass being common. The linings and baffles can be flat, contoured, constructed from layers of different materials, or mixed and matched for a particular application. Absorptive materials may face challenges due to harsh conditions such as high temperatures and potential clogging from particulate-laden flows. Dissipative mufflers are best suited for moderate-to-high frequencies, since absorption is less effective at low frequencies. At frequencies where the absorptive materials are effective, the attenuation is broadband, and the passbands exhibited by reactive mufflers are reduced or eliminated. Compared to reactive mufflers of similar size, dissipative mufflers can have higher attenuation (except at resonances for the reactive muffler) and lower pressure drop. At higher frequencies, where the acoustic wavelength is smaller than the duct width, the attenuation of a dissipative muffler may decrease considerably. See also Sound absorption.

Active mufflers attenuate unwanted noise by adding sound to counteract it. The disturbances add algebraically, resulting in a cancellation of the unwanted sound. An active muffler consists of sensors (such as microphones), a controller, and actuators (such as loudspeakers). The controller unit processes the signals from the sensor, and computes an appropriate signal for the actuator. Numerous control systems and strategies exist, and are under continuous development. Active mufflers are best suited for low frequencies where the sound field is relatively simple. The effectiveness of active mufflers has been demonstrated for a number of situations, but several challenges are the topic of ongoing research. There is a need for ruggedsensors and actuators that can withstand high temperatures and harshenvironments. Also, high-intensity disturbances at low frequencies requirelarge-displacement, high-power actuators.

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This article is about the exhaust system component. For other uses, see Muffler (disambiguation).

Muffler(silver) and (connecting pipe) exhaust pipe on a Ducati 695

A muffler (or silencer in British English) is a device for reducing the amount of noise emitted by a machine. On internal combustion engines, the engine exhaust blows out through the muffler. The internal combustion engine muffler or silencer was developed in parallel with the firearm suppressor by Hiram Percy Maxim. ^[1]

Contents 1 Description 2 Advantages 3 Mini-mufflers 4 Types and positions of mufflers 5 References 6 External links

Description

Dual exhaust pipes attached to a car's muffler

Mufflers are typically installed along the exhaust pipe as part of the exhaust system of an internal combustion engine (of a vehicle, or stationary) to reduce its exhaust noise. The muffler accomplishes this with a resonating chamber, which is specifically tuned to cause destructive interference, where opposite sound waves cancel each other out. Catalytic converters also often have a muffling effect. The effect is mainly generated largely by restriction, rather than by cancellation.

Advantages

Mufflers that reduced backpressure relative to earlier models became increasingly available in the late 20th century, and resulted in increased engine efficiency, performance, power output, and simultaneously decreased overall wear and tear on the engines' components, as well as sound to levels in compliance with the law.

Mini-mufflers

A mini-muffler (also known as a "hotdog" in the auto industry) can be put in place of a normal muffler in a car exhaust system to "enhance" the sound of the exhaust for a car enthusiast. These are smaller, cost usually about half the price of a normal muffler and work in a similar way, but allowing more sound through. Changing the muffler / mini-muffler / catalytic converter combination can change the sound of a car's exhaust system considerably. Deliberately removing a muffler from a "factory" setup or using a muffler that is defective due to rusting risks the resulting noise being over government approved noise levels, and possible action by law enforcers. Nevertheless some motorcycle owners remove their mufflers just to make them louder.

Types and positions of mufflers

A muffler of a large diesel-powered truck

• With cars, lengthwise underneath, blowing backwards at the rear
• to the sides before the rear wheels.
• With large diesel-powered trucks:-
  • Mounted vertically behind the cab
  • Crosswise under the front of the cab, blowing sideways.
• With motorcycles:
  • Usually, beside the engine and rear wheel blowing backwards.
  • In more modern motorcycles, under the seat blowing backwards from under the back of the seat. (Under-slung)
  • Under-engine exhausts first reached popularity with Buell motorcycles, though by 2008 most manufacturers began using the under-engine design as well.

Motorcycle enthusiasts sometimes use the term "raygun," "drag pipes" or "pea-shooter" for the old shape of motorcycle exhaust silencer/muffler with a long straight cylindrical barrel that merged roundedly at each end into the pipe, as in this image and this image.

Schematic view of gas flow in a piston engine. 1 Ram air, 2 Air filter, 3 mass flow sensor, 4 butterfly valve, 5 air box, 6 intake runners, 7 intake valve, 8 piston, 9 exhaust valve, 10 extractor pipe, 11 collector, 12 catalytic converter, 13 muffler

References

1. ^ "Hiram Percy Maxim". Encyclopædia Britannica. http://www.britannica.com/ebc/article-9051539. 

External links

• Howstuffworks: "How Mufflers Work"

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Dansk (Danish)
n. - halstørklæde

Nederlands (Dutch)
knalpot, geluiddemper, sjaal, want

Français (French)
n. - cache-nez, (US, Aut) silencieux

Deutsch (German)
n. - Schal, Auspufftopf, (Schall)dämpfer

Ελληνική (Greek)
n. - κασκόλ, (μηχαν.) (ΗΠΑ) σιγαστήρας (κν. σιλανσιέ), (μουσ.) σουρντίνα

Italiano (Italian)
marmitta, silenziatore, sciarpa pesante

Português (Portuguese)
n. - cachecol (m), silenciador (m) (Mec.)

Русский (Russian)
кашне, глушитель

Español (Spanish)
n. - silenciador, sordina, bufanda

Svenska (Swedish)
n. - (ylle)halsduk, dämmare

中文（简体）(Chinese (Simplified))
围巾, 厚手套, 头巾

中文（繁體）(Chinese (Traditional))
n. - 圍巾, 厚手套, 頭巾

한국어 (Korean)
n. - 목도리, 소음기

日本語 (Japanese)
n. - マフラー, ずきん, 消音器, 響き止め

العربيه (Arabic)
‏(الاسم) لفاح, كمامه‏

עברית (Hebrew)
n. - ‮עמם-פליטה, צעיף, סודר‬

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