How to design and plan for Acoustics
Leave a CommentBenefits during the initial design
There are new methods and processes that are constantly changing the game for designers. Partially the reasoning for this problem is the ever-growing challenges designers face every day.
Development Speed: Constant Revision and parts not being efficient or poor quality
Complexity Management: If the project is overly complex, usability and budget can be difficult. This increases risk and chances of error.
Customer Involvement: Keeping potential customers involved is tricky. Questions are needed to get the appropriate feedback that will help move the project forward.
Sustainability: You can have a killer design idea, but either the products aren’t sustainable on either an economic or environmental level. Costs are too high for large quantity production not to mention recyclable or minimizing the use of materials ensures good global citizenship.
So first, keeping all the challenges in mind how do you not only address key product design issues, but design to reduce noise and more importantly manage cost? Well, let’s look at the benefits of providing a Sound Solutioned Environment.
An environment that provides reduced noise levels increases efficiency and improves output and can minimize hearing loss claims. In a classroom, It can increase learning capabilities and clear speech. According to the United States General Accounting Office “21,900 schools exhibit poor acoustics or noise control, affecting over 11 million students. 28.1% of all schools reported unsatisfactory or very unsatisfactory environmental noise conditions. This was higher than ventilation (27.1%), physical security (24.2%), indoor air quality (19.2%), heating (18.9%), or lighting (15.6%)” Reducing noise in the workplace can have health benefits by reducing Cardiovascular Disease and Workplace distractions.Global Analytics writes ” Businesses lose about $600 Billion Dollars a year in workplace distractions” You get the picture. Basically, NOT designing for noise can be expensive. So let’s look at the different types of noise, how to discover acoustical mistakes BEFORE they are made, and important key design elements to consider.
Air Borne or Structure Borne
What is Airborne Noise? Airborne Noise is a condition when sound waves are being carried by the atmosphere. Examples are Engine Noise, Turbo Whine, and Fan Noise…Structure-borne Noise is Mechanical Vibration in a structure which can become an audible sound. Example: Mounted Devices, Sheet Metal Structures, and Body Panels.
Airborne noise can be reduced through proper design elements and acoustical treatments. The primary consideration in design to reduce airborne noise is to make sure that all air paths, in or out of the enclosure are tortuous. This eliminates the line of sight noise transmission. Another design consideration is to ensure that all doors and access panels are properly fitted and gasketed to provide a complete seal. As little as 10% untreated surface areas will reduce the effectiveness of acoustical treatments by up to 50%. All interior surfaces of the enclosure should be treated using the proper acoustical absorber or absorber/barrier composite.
Structure-borne noise can be reduced by considering the nature of the structure-borne sound which can vary significantly depending on the source of the vibration, the composition of the structure through which it will transmit. The radiating surface and the character of the receiving space.
Key Design Issues
When looking at using the right products you should know that there is no such thing as one right material for all applications. For example, Barrier composites only need to be used between noise sources and OCCUPIED areas. Absorber products are less expensive, lighter and will make a major impact that will fill gaps and voids. More is not always better. If there is more than 5% untreated area, don’t waste money by adding mass. Something that happens quite often is the absorber is often covered. Covering the Absorber negates its purpose. There are other ways to get the look you want like with different facing combinations so it’s important to consider the environment and know the frequency. All acoustic products have a signature. We can help you pick the right one for your application
Key Take Away’s
- Treat as close to the source as possible
- Block the Noise Paths
- Leave room for treatment
- Use the right products
Treat at the source, Block the path, and Plan for materials
Treat at the source
- When you treat close to the source of the noise; if can you treat smaller areas and you eliminate secondary effects. For example, soft engine mounts to isolation engine vibration and stop structure-borne noise. Soft mount gensets, inverters, and other equipment. Use sound shields/enclosures around equipment where possible.
Block the noise paths.
- Structure Borne noise will travel along all rigid hard connections until it finds a sympathetic surface to radiate sound. To solve this problem, you can introduce isolation barriers where practical. Airborne noise will follow all air paths and reflect off all hard surfaces. Here, you can make sure all air paths are either sealed or “tortuous”. You can line as much surface area as possible with sound absorbers or absorber/barrier composites.
Plan for Acoustic Materials
- Be sure to leave space for treatment. Minimize equipment attached directly to bulkhead adjacent to occupied areas by either stand-off the attachments or attempt to make attachments on the outboard or other non-occupied bulkheads. Be sure to leave room between hulls, bulkheads and other structures for the application of sound absorbers and composites. We would typically recommend a 3″ recommended clearance.
Common myths
There’s is no such thing as 1 material for all applications.
– Barrier composites only need to be used between noise sources and OCCUPIED areas. You can also use absorber product because it’s cheaper and lighter and will make a major impact in reducing noise if you fill all the gaps and voids.
More is not always better.
-Too much over-engineering has been done in the past. If there is more than 5% untreated area, don’t waste money adding mass.
Keep these rules in mind:
1.) Don’t cover the absorber
- Covering the absorber negates its purpose. There are other ways to get the look you want.
2.) Find the right mounts
- Many equipment manufacturers do not do the work required to provide the best vibration isolation mounts.
3.) Consider the environment
- If the product will be exposed to heat, water, diesel, gas, etc make sure it’s going to stand up.
4.) Know the frequency
All acoustic products have a signature. Pick the right
