Experiencing Sound Insulation
One has certainly experienced sound insulation within a building. For example, one may have been annoyed by the discussions held in the office next door, or one may have been puzzled to hear people talking at night in the flat next door.
When the sound source and the receiver are located in different rooms, we will talk of insulation. The sound level difference will be defined as the sound level in the source room minus the sound pressure level in the receiving room.
One will, however, find that with the same construction technique applied, the resulting sound insulation is not similarly perceived, depending on the dimensions of the room, the nature of its cladding, and the nature of the walls and floors around. This means that a specific quantity must be defined to characterize the wall or the floor independently of its environment: this is known as the sound reduction index that can be measured in the sound insulation test suite of an acoustic laboratory.