Micro perforated plate

Micro perforated plate

A Micro Perforated Plate (MPP) is a device used to absorb sound, reducing its intensity. It consists of a thin flat plate, made from one of several different materials, with small holes punched in it. An MPP offers an alternative to traditional sound absorbers made from porous materials.

Contents

Structure

An MPP is normally 0.5 - 2 mm thick. The holes typically cover 0.5 to 2% of the plate, depending on the application and the environment in which the MPP is to be mounted. Hole diameter is usually less than 1 millimeter, typically 0.05 to 0.5 mm. They are usually made using the microperforation process.

Operating principle

The goal of a sound absorber is to convert acoustical energy into heat. In a traditional absorber, the sound wave propagates into the absorber. Because of the proximity of the porous material, the oscillating air molecules inside the absorber lose their acoustical energy due to friction.

A MPP works in almost the same way. When the oscillating air molecules penetrate the MPP, the friction between the air in motion and the surface of the MPP dissipates the acoustical energy.

Comparison with other materials

Traditional sound absorbers are porous materials such as mineral wool, glass or polyester fibres. It is not possible to use these materials in harsh environments such as engine compartments. Traditional absorbers have many drawbacks, including pollution, the risk of fire, and problems with the useful lifetime of the absorbing material.

The main reason why Micro Perforates have become so popular among acousticians is that they have a good absorption performance but without the disadvantages of a porous material. Furthermore, an MPP is also preferable from an aesthetic point of view.

History

For a while, perforated metal panels with holes in the 1 – 10 mm range have been used as a cage for sound-absorbing glass-fiber bats where large holes let the sound waves reach into the absorbent fiber. Another use has been the creation of narrowband Helmholtz absorbers which can be tuned by hole size and the dimensions of the hole distance and air gap behind the panel. However, when the hole dimensions are in the region of 0.05 - 0.5 mm, the narrow absorption peaks become much wider, making the additional fiber absorber more or less unnecessary, while still maintaining a very high absorption factor. By varying geometrical and material parameters, the acoustical performance can be tailored to meet a multitude of specifications in various applications.

The theory of micro perforated plates as sound absorbers originates from Professor Daa-You Maa.[1][2] Further possibilities aiming to improve the accuracy of Maa’s original model are currently being investigated. One other major phenomenon that currently being investigated is the nonlinear effect i.e. an MPP behaves differently depending on the magnitude of the incident sound wave.[3]

References

  1. ^ Daa-You Maa (1975). "Potentials of micro perforated absorbers". Journal of the Acoustical Society of America 104 (5): 2868–2866. 
  2. ^ Helmut V. Fuchs, Xueqin Zha (2006). "Micro Perforated Structures as Sound Absorbers - A Review and Outlook". Acta Acoustica united with Acoustica 92: 139–146. 
  3. ^ Hans Bodén, Ying Guo, Hüseyin Bora Tözün (8–10 May 2006). "Experimental Investigation of Nonlinear Acoustic Properties for Perforates". 12th AIAA Aero Acoustic Conference. Cambridge, Massachusetts. 

External links


Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • Perforation — For perforations in an oil well, see Perforation (oil well). For perforation in medicine and surgery, see Organ perforation. A perforation is a small hole in a thin material or web. There is usually more than one perforation in an organized… …   Wikipedia

  • MPP — or M.P.P. may refer to:* Marginal physical product * Marijuana Policy Project, organization in the United States * Massively parallel processing, in parallel computing ** Goodyear MPP, an early implementation of massively parallel processing *… …   Wikipedia

  • Absorption (acoustics) — Absorption refers to the absorption of sound waves by a material. The absorption is the missing piece , when comparing the total reflected and transmitted energy with the incident energy. It is the property of a material that changes acoustic… …   Wikipedia

  • Cathode ray tube — Cutaway rendering of a color CRT: 1. Three Electron guns (for red, green, and blue phosphor dots) 2. Electron beams 3. Focusing coils 4. Deflection coils 5. Anode connection 6. Mask for separating beams for red,… …   Wikipedia

  • History of the single-lens reflex camera — The history of the single lens reflex camera predates the invention of photography in 1826/27 by one and a half centuries with the use of a reflex mirror in a camera obscura first described in 1676. Such SLR devices were popular as drawing aids… …   Wikipedia

  • Marsh rice rat — Temporal range: Rancholabrean (300,000 years before present) – present Conservation status …   Wikipedia

  • Heat exchanger — An interchangeable plate heat exchanger Tubular heat exchan …   Wikipedia

  • Glossaire du cinéma — Glossaire de termes relatifs au cinéma. Sommaire : Haut A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 1 à 9 16 mm …   Wikipédia en Français

  • Crucible — For other uses, see Crucible (disambiguation). A modern crucible used in the production of silicon ingots via the Czochralski process A crucible is a container used for metal, glass, and pigment production as well as a number of modern laboratory …   Wikipedia

  • art conservation and restoration — Maintenance and preservation of works of art, their protection from future damage, deterioration, or neglect, and the repair or renovation of works that have deteriorated or been damaged. Research in art history has relied heavily on 20th and… …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”