Category Archive: Acoustics 101

The (not so) Silent Threat to American Classrooms

The (not so) Silent Threat to American Classrooms and ways to address it.

Noise is everywhere. Unless it’s a movie or naptime, you can’t really find a quiet place inside a school. Especially, the place where quiet should matter the most; the classroom.    

Inside the classroom image

The impact that noise has on classrooms can be easily overlooked. You don’t think about the hmm of the air conditioner or the rattle of the pipes, but experts believe that students miss up to 33 percent of learning material because they can’t understand what’s being said. Children who are especially sensitive; socio-emotional or those whom have learning, or behavioral challenges for example are more susceptible to the impacts of noise. Not the mention the teachers who suffer from vocal strain trying to talk over the noise.    

The National Heart Association says chronic noise can cause elevated stress responses in the human brain. This is especially straining for students because unlike adults, children haven’t developed the ability to interpret meaning from words that they don’t fully understand.  

 Noise pollution from outside noise, HVAC units, the humming of lights can have serious health and cause performance impacts on students. For example, an air conditioner found in Decatur, GA aka “the beast” is a staggering 60 decibels. Schools do take the performance of their districts seriously. However, noise inside of the classroom is not a priority. To reduce noise levels and bring awareness to noise issues in schools the American National Standards Institute in 2002 published a set of standards to be used by designers, school planners, and school districts that dictates maximum noise and reverberation levels in classrooms. (ANSI_S2.60) Keep in mind that this, however is not a requirement. It is recommended that decibels levels in schools not exceed 35 decibels. It has been recorded by researchers that noise classroom can reach between 66 to 94 decibels! In a TED Talk by sound expert Julian Treasure, he makes it clear that Architects need to use their ears as well as their eyes. Here are some solutions to show you how. 

Solutions

Keep in mind

Sound is lazy and will always take the easiest path to get from point A to B. The easiest path for sound to travel is a clear unobstructed path. If you can visually see the noisy machine, there is nothing obstructing or reducing the noise from the maximum amount that you can receive. It is important to not only place something in-between and the noisy machine but also to make sure that there is no place for the noise to slip through the holes and cracks.

Structure Borne vs Air Borne Noise

Structure Borne noise is cause by vibration the different components. The vibration can cause structures as well or sheet metal to resonate. Initial design can control a large portion of this problem. The preferred method of controlling residual structure-borne noise is to isolate the cause of the vibration.

Air Borne Noise can be reduced through proper design elements and acoustical treatments. The primary consideration in design to reduce Air Borne Noise is to make sure that all air paths in or out of the enclosure are tortuous and to ensure that all large flat sound reflecting surface are treated with appropriate soft sound absorbing materials.

Know the causes

Heating and cooling systems play a major part in excessive classroom noise because to save dollars, schools often place HVAC units in each classroom instead of a centralized system. Individual units typically are nosier. Another reason for the excess noise is the lack of Acoustic Standard being applied to building codes in the same fashion as lighting and ventilation. Ensuring that equipment used in and around classrooms is manufactured to the quietest possible standards is the easiest way to reduce unwanted noise in the classroom.

Absorbers vs Barriers

When you’re not really sure what solution you’re looking for you usually search for “soundproofing”. We receive calls that sound like “how do you make this oxygen air compressor quiet?” Or Is there a way to soundproof my office?

People are convinced that soundproofing foam, sound absorbing foam or soundproofing panels are the “cure all”. Well, doesn’t foam stop sound?  No. Foam doesn’t “stop” sound. It absorbs echo. This is a common misconception that follows confusion when OEM’s and everyday people are looking for sound solutions for their next project.  Let us help you understand the difference and which one is best for your next project.

What is an Absorber?

Technicon Acoustics Foam for Sound Absorption

 

First, let’s determine what an Absorber does. Sound absorbers are porous materials used to line hard sound-reflective surfaces to reduce airborne noise. Airborne noise is a sound that is transmitted through the air, typically generated by

 

 

  • Speech
  • Television and Radio
  • Animal Sounds
  • Transport

In construction, you typically find structure-borne noise which is transmitted through a solid structure, such as steel, wood, concrete stone etc. Once the sound strikes the material, the sound energy is dissipated as heat. Typical absorbers used are acoustical foams and fibers. At Technicon Acoustics we produce absorbers that are acoustical foams and fibers for both functional and aesthetic purposes with a wide variety of foam or non-woven absorbing materials. Common examples of sound absorbers are open cell foam and polyester fibers. To determine the amount of material necessary to reduce the noise, our engineering team uses our Acoustics Lab to ensure there are no gaps, cracks or leaks to allow sound to escape from the enclosure.

Common Uses of Sound Absorbers

• Machine enclosures

• Generator, air compressor, & water pump enclosures

• Engine compartments

• Truck & heavy equipment cabs

• Home appliances

• Medical equipment

What is a Barrier?

Barrier Composite

Barriers (soundwall, noise wall) are slightly different than absorbers because they are used to block noise transmitting from one location to another. A Sound Barrier is a Mass Loaded Vinyl (MLV) used to reduce the amount of airborne sound transmitting through a wall, 

 

floors, ceilings etc.

While Barriers are heavy as lead, they usually aren’t that thick. This allows the MLV to improve Sound Transmission Loss without taking up space; like at a Construction Site. Barriers can be wrapped or be used with other material like our Thermal Solution Product Tech Shield.

*Keep in mind, that noise can be absorbed by sound absorbers or blocked by a barrier. We can also reduce structure-borne noise that causes vibrations using our Damping Material. *

Common Uses for Sound Barriers

• Machine enclosures

• Engine compartments

• Firewalls

• Bulkheads

• Cab floors

• Pipe Wrap

To view, our case studies and additional applications go to www.techniconacoustics.com or if you just have more questions. Click to request a chat with the Sales Team .

 

The Cost of Noise

On average the CDC reports that in 2007, “82% of the cases involving occupational hearing loss were reported among workers in the manufacturing sector” Hearing Loss is the most commonly recorded occupational illness in Manufacturing accounting for 1 in 9 recordable illnesses. It’s estimated, that there are 16 million people working in the Manufacturing Sector, which accounts for approx 13% if the US workforce.

Hearing loss disability results in an estimated $242 million dollars worth of workers compensation payments each year. According to hear-it.org. As many as 95% of construction workers are exposed to high levels of noise on a daily basis. When left untreated, hearing loss can reduce earnings by as much as $30,000 a year. The top industries that have the most hearing loss claims? Construction, Carpentry, Farmers, and Mining resulting in 30 million work-related injuries each year. The machines that caused the most noise are Jackhammers, Dump trucks, Cement Mixers, Electric Saws. Plant work and Power Stations resulted in 100 DBA ( A-weighted decibels) with Sewer water and Residential Construction sites following behind between 93-99 DBA. *see how to measure noise on a construction site*

Most will argue that the primary cause for the hearing loss injuries in Manufacturing, Construction, Mining etc is that there’s a lack of educational training on how to prevent Occupational Hearing Loss. According to Mr. Neitzel’s report:

“Occupational health regulations governing the construction industry, including those pertaining to hearing conservation, are generally less comprehensive than those for the general industry. As a result, health surveillance and prevention programs for chronic diseases such as NIHL are limited in the industry. The US Occupational Safety and Health Administration (OSHA) has two regulations pertaining to hearing conservation in the construction industry. The first… set forth an eight-hour time-weighted average (TWA) permissible exposure limit of 90 dB, and requires a hearing conservation program (HCP) for workers whose exposures exceed this level. The second, [regulation] requires the use of hearing protection devices (HPDs) when noise exposures cannot be reduced below the Permissible Hearing Levels PEL.”

Source: healthyhearing.com

See the Story on how poor acoustics affects farmers Source: National Geographic

How to solve it

Marine

Whatever kind of boat you build, your customers will appreciate your efforts to make it quieter. Engine noise, prop cavitations, shaft whirl, all generate noise and create a vibration that can be controlled with the right noise control materials. Here’s our recommendation for a 47″ Trawler Yacht.

  • Engine Room – Use Absorber/Barrier composites. The absorber layer reduces reverberant noise. The barrier layer reduces sound transmission from the engine compartment.
  • Bulkheads – Here, you can also use an absorber and barrier. Either separately or in a composite to reduce reverberant noise and block sound.
  • Hull Structure – Treat hull and deck vibration with proper damping materials.

How to measure reverberant noise

Transportation

Operators of Transportation products such as trucks, buses, trains and emergency vehicles spend their entire day in the vehicle. The major noise sources in a vehicle are the engine, accessories, road and wind noise. Noise can enter the operator and passenger compartments by a variety of paths – through the glass, dash, floor doors etc.

  • Flooring Systems – Road Noise is generated by the vehicles passage over the highway surface and resulting tire and air noise. By using a Barrier Composite you can reduce the impact of road noise on the operator and its passengers.
  • Body Panels – Large surfaces such as floor pans and door panels are prone to vibration. Typically, the greater the surface the greater the noise. Vibration damping materials applied to these surfaces reduce vibration – radiated noise.
  • Hood Liners -These can be manufactured to act both sound absorbers and Heat Shields. They can reduce the reverberant engine noise thus improving both the outdoor environment and the cab interior. They can be made with a protective, heat-resistant facing and sound-absorbent material.

Heavy Equipment

Major noise sources in heavy equipment are the engine, drive train and power take-off systems. The sound radiates throughout the environment and affects operators, bystanders, nearby businesses and individuals.

Read the blog: Tuning into Urban Noise

  • Operator’s Cab- Headliners and sidewall trim systems that incorporate sound absorbers and sound barriers can be used to block sound entering the operator’s compartment and absorb sound reflection from within the operator’s cab. (Contact us to see which facings can be used for functional and aesthetic purposes.
  • Firewall and floormat systems- Firewall composites block sound from the engine and drive train and prevent noise from entering the cab. These can be manufactured either with or without a heat shield component. Sound barriers bounded to a durable wear surface create floormats that reduce sound transmission and improve operator comfort.

Technicon Acoustics did a case study on measuring and decreasing noise in the cab of a motor grader. Click here to see the results

Contact Us

See our list of Solutions and Capabilities at www.techniconacoustics.com and request a consultation with our Sound Solution Sales Team.