In growing metro cities, there are many instances in our day-to-day life where we come across noise intrusion from outdoors, from the next room or from conversations in meeting rooms. Imagine if movie theatres were not adequately isolated, especially in closely packed multiplexes, the movie experience can be completely spoilt by noise transmission between the theaters. All of these can be avoided when the space under consideration is tested and treated appropriately with the right materials. The effectiveness of these treatments is generally rated by Sound Transmission Loss (STL) properties, meaning STL quantifies the amount of sound energy that is prevented from traveling through the acoustic treatment.


Examples of some acoustically treated spaces

There are 2 popular methods for determining STL of a material:


  • Impedance tube method – This method helps to research acoustical materials that could be implemented for developing noise control products, verifying material compliance with standard regulations, etc.
Impedance tube setup


  • 2 room method - while the impedance tube method helps in researching acoustic material properties, the 2-room method is done for determining the overall STL by large surface partitions like panels, doors, windows, vehicle dashboards etc.,
2-room measurement setup

An acoustic treated partition wall, for example, is a major object/structure, standing between the source and receiver space, that contributes to absorbing, reflecting and transmitting the incoming noise, therefore, treatment is primarily done to the partition wall. While most of the focus is on the material used for treating the partition wall, importance is also given to the source and receiver space characteristics like its shape, volume, false ceiling, functional importance of the room, etc.

Components of sound through acoustic barrier

Theoretically, the sound transmission loss of an acoustical barrier depends on mass and stiffness of the material which in-turn determines the natural frequency of the material. This is a crucial factor to consider because the noise generated by the sound source may contain frequencies that excite the natural frequency of the barrier causing the noise to easily pass through, thereby defeating its entire purpose.


Engineers generally want to consider using a material that has a higher mass per unit area i.e., density. The idea behind it being that the heavier the material, less likely it will vibrate in response to the sound generated by the source. However, practical boundary considerations sometimes limit the usefulness of this method.


Some examples of the materials used for treatment are Autoclaved Aerated Concrete (AAC), Laminated glass, Expanded polystyrene, rockwool etc...


Rockwool and acoustic foam

With years of applied experience and real-life task exposures, NV Dynamics has developed credible knowledge in both using these materials based on their merits of the situation and as well as considering the typical outputs to be derived. These are well complemented by the latest software and hardware tools that make noticeable differences to the quality of results and their interpretations. Get in touch with us to know the variety of cases we have handled and how our expertise can help you solve your case.