Whilst the humble sound attenuator may be a relatively simple product, it carries a degree of complexity in its design.
How do splitter attenuators work?
When addressing noise control problems, we often need to implement a combination of measures for acoustic enclosures and ventilation attenuators. To the layperson, it is quite easy to imagine how an acoustic enclosure or acoustic panel system works, in that this is a physical barrier blocking the line of sight and providing some mass between the source and receiver to reduce noise. However, when considering an acoustic splitter attenuator with open airways, the fact you can see the noise source from one end yet still achieve a high level of noise reduction can be difficult to comprehend.
First of all, let’s consider what an attenuator is.
An attenuator comprises of an outer casing, usually steel, though can be any opening for ventilation, (eg. concrete shaft / tunnel or builders work), with a number of ‘splitters’ or ‘baffles’ arranged symmetrically. These splitters are essentially individual casings filled with an acoustically absorbent media (eg. mineral fibre, fibreglass or acoustic foam), and usually with a perforated steel sheet to provide some resistance to impacts, whilst allowing a good open area to retain the acoustic properties of the retained materials. A typical attenuator will comprise multiple acoustic splitters and airways.
As sound waves pass along the length of the attenuator, they are absorbed into the acoustic insulation with the sound energy converted into tiny amounts of heat energy. The combination of the number and size of acoustic splitters and airways allows the acoustic performance of the attenuator to be varied to meet the required noise reduction.
There are several key rules in selecting the best attenuator for the job:
- Thicker splitters for low-frequency noise reduction, thinner splitters for high-frequency
- The higher the free area (eg. ratio of airway area vs. splitter area), the lower the performance
- The longer the attenuator, the better the performance
Do splitter attenuators affect airflow?
When installing any item, including a splitter attenuator, into a duct or shaft used for airflow it increases the pressure in the system. This is particularly important when considering a retro-fit solution, as any additional pressure will result in a corresponding reduction in airflow. Therefore, when selecting and designing attenuators it is just as important to design correctly for airflow as it is for acoustics.
With the number of factors involved, the design and selection of attenuators for ventilation systems can be a challenge to meet acoustic and aerodynamic parameters, whilst also checking that the physical size can be accommodated.
Should you have a requirement for the design and supply of industrial splitter attenuators or our other range of noise control products, please contact us.
If you have any questions or would like more information on our products and services, please contact Wakefield Acoustics at +44 (0) 1924 418 940 or email via [email protected].