Absorption in a Room and Combating Unwanted Sounds Coming from the Outside

Myth: Absorption is not the right solution for sound isolation issues, however, absorption in the room does help.

Most people recognize that absorption is not the right solution when trying to attenuate sounds coming into the room from the outside. For sound blocking, we should use the right construction and treatment materials. There are a wide variety of reasons that unwanted sound can get into the room. Inadequate wall construction, openings above drop ceiling between rooms, HVAC ducting breaches, structure born transmissions . . . the list is long and so is the list of solutions.

Sometimes absorption may help a little, but not often. Because high frequencies can be easily blocked, unwanted sounds that come into the room are almost exclusively low-mid or low frequencies. Most absorptive solutions do not efficiently treat the lower frequency bands. The sounds are going to come into the room.

If the problem is that outside noise is disturbing the voice intelligibility of conversations within the room, then absorption in the room can reduce the reverberation and make voice communication more effective – that does not reduce the level of unwanted sounds coming into the room. However, if the problem is distraction caused by the outside sounds, absorption will not help. We just cannot turn off the brain’s processing when we can make out all or some of the voice content.

On rare occasion, absorptive treatments can make the incoming sound more easily deciphered. So, if privacy of the incoming sound is at issue, we must be careful not to make things worse by enhancing the intelligibility of outside conversations.

Glossary of Terms

Acoustic absorption refers to the process by which a material, structure, or object takes in sound energy when sound waves are encountered.

Sound Isolation refers to the process of attenuating airborne sound between adjacent spaces.

Voice Intelligibility indicates the ability of a listener to understand voice content in a given acoustic environment.

 

Chuck Chiles, Director of Technology, Unika Vaev Acoustics