Question:

• What is a wall / ceiling system with good noise absorption rating ?

   

Answer:

• Sound waves, when striking any surface of walls, ceilings, floors, roofs made of hard, heavy materials such as concrete, bricks, solid timber, gypsum boards, glazing, etc., will reflect many times among these surfaces and gradually decrease their amplitudes, hence, in some particular environment, might create reverberance (echos). Reverberation time is the time required, measured in seconds,  for reflections of a direct sound to decay by 60 dB below the level of direct sound. Reverberation times with higher values will result in stronger echos, and in some cases, will adversely affect the intelligibility of speeches to audience.

   

• Vietnamese language is a monosyllable language, whereas official languages of countries in Europe (UK, France, Germany, Spain, Portugal, Russia, Finland, Sweden, etc.), Americas (USA, Canada, Mexico, Brazil, Argentina, etc.), and Oceania (Australia, New Zealand, etc.) are polysyllable languages. For monosyllable languages, the reverberance seems to have no or very little adverse effects on the intelligibility of students and audience. Therefore, in Vietnam, students of all ages still hear and understand clearly lessons spoken in their mother language, and so do audience when listening to speakers, regardless of the fact that classrooms, meeting rooms, conference halls are not noise absorption treated. However, for polysyllable languages, reverberance is a major concern for all listeners, be them very young pupils or adults. Thus, in developed countries, surfaces of walls and ceilings in areas such as classrooms (from preschools to universities), meeting rooms, conference halls, recording studios, etc. must be treated with special sound absorbing materials to reduce the reverberance to acceptable levels; in other words, to achieve expected reverberation times.