To get the best out of an acoustic material, like gypsum ceilings or tiles, you need to consider three critical factors:
- Absorption profile: How much sound does the material absorb at different sound frequencies? This is measured in a lab and expressed as an alpha value or NRC value. The goal is to have an even absorption profile – because you want all sound frequencies to lose energy at the same time.
- Reverberation time: How much of the material is needed to achieve a given reverberation time in a room? Reverberation time is the time needed for the sound to lose energy by 60dB. It’s often calculated and expressed in seconds.
- Placement: Knowing that sound moves in all directions, where is the best place to put the acoustic material? Our studies show that in a classroom you can achieve the same reverberation time and use 10% less acoustic material, if you place acoustic material equal to 15% of the ceiling surface on the walls, rather than just covering the ceiling.