Slim loudspeakers in the window frame reduce noise from outside

Slim loudspeakers in the window frame reduce noise from outside

Technology News |
By Christoph Hammerschmidt

The core of the Fraunhofer development is a very slim loudspeaker that owes its slimness to the fact that it is not using an extensive voice coil. Instead, the tiny rectangular loudspeaker is designed as a layered stack of electro-active polymers (EAP). This has the double benefit of allowing very compact loudspeakers and in addition it is very cost-effective, said researcher Oliver Heuss.

Besides the application in sound-insulating windows even in very noise-sensitive environments such as recording studios, the device can also be used to make conference rooms bug-proof, at least in part: Because the integrated loudspeakers prevent the sound of the conversation within the room from escaping, or at least it suppresses it to some extent.

The EAP stacked actuator is composed of multiple alternating layers of elastomers and electrodes. A high-voltage static field that can be modulated with a “sound payload” is applied to the stack. The Design from the Fraunhofer researchers calls for metallic electrodes that a have multiple microscopic holes. Thus, the elastomers – a material that is not compressible – to develop local deformations during operation. Electrodes as well as elastomers can assume any shape which ensures great design flexibility.

In the past there have been several attempts to attack the noise problem with piezo actuators. However, they needed to be attached to the window more or less in the middle of the glass surface which produced an undesired esthetic appearance. In contrast, the new EAP loudspeakers from Fraunhofer LBF can be integrated into the window frame. In addition, these loudspeakers can actively control the acoustic pressure between the window panes and thus reduce the acoustic transfer characteristics.

Even with a loudspeaker of just 20 cm length (equaling 7% of the window frame length), it was possible to reduce the noise by 3.3 decibels at frequencies down to 500 Hz.A stronger effect can likely be achieved if the loudspeaker area is further increased. It also can be expected that the effect can be increased if multiple microphones are installed in the space between the windowpanes.

Further information:

If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :    eeNews on Google News


Linked Articles