Thermal conductivity and sound absorption

A building ought to be warmer than the outside air in cold climates and cooler than the outside air in hot climates. Heat flows to a cooler area like water flows to a lower level. The flow continues until outside and inside temperatures are equal. Heat movement takes place by conduction through any solid object that separates areas of different tempera­tures. The rate at which the movement of heat takes place varies with the material through which the heat passes. The rate is measured as thermal conductivity (U) of heat (in British thermal units (Btu)) that is transmitted per square foot of cross section per hour per °F difference in temperature between the two sides of the material. Insulation, which is material with a very low U, is used in order to make the rate of heat flow as low as possible. The U of a material varies directly with its density. The best insulation, expanded plastic foam, consists of bubbles with the proportion of solid material less than 1 percent of the volume and the rest consists of air or gas. Insulation is also made of other porous material. However, some structural materials also have a low U factor and therefore serve as insulation. Wood and certain types of lightweight concrete are two such materials.

Sound Absorption Loud sound should be avoided in most buildings and has to be reduced by the use of acoustic material which is to absorb it, whether it is produced in the building or outside. Sound is absorbed by air spaces in the material. Porous material is used, or material is fabricated with a pattern of openings so as to be able to absorb sound. Wood and porous concrete are the most effective in sound absorption.

Notes:

bubble n. пузырь, пузырёк

cool adj. прохладный

expanded plastic foam пенопласт

loud adj. громкий

porous adj. пористый

sound absorption звукопоглощение

warm adj. теплый

Ответьте на вопросы к тексту.

1. What ought a building to be in cold climates and in hot climates?

2. What is the reason for that?

3. What is the cause of heat movement?

4. What does the rate of heat movement depend on?

5. How is the rate of thermal conductivity measured?

6. What is insulation?

7. Why is expanded plastic foam the best insulation?

8. What other materials have good insulation?

9. How should loud sound be reduced?

10. What is sound absorbed by?

11. What materials are the most effective in sound absorption?

Date: 2016-02-19; view: 792; Нарушение авторских прав