Category Archive: Uncategorized

Micro Perf Myths

Controlling how and when sounds are absorbed is pivotal for equipment and machinery. Acoustic designers use a combination of tactics and materials to control sound absorption and direction. One method manufacturers use is adding layers of composite materials, foams, and films to create panels with different rates of absorption.

Micro perf, or micro perforation, is a film with tiny holes. Manufacturers apply this perforated film to acoustic foams to help absorb noise. Ideally, this addition should make the acoustic foams and composites absorb sounds at lower Hertz levels without adding mass or weight to the foam. However, an internal study found this was not the case, as micro perforated materials that were tested alongside unperforated materials provided minimal distinctions in sound absorption.

What Is the Proposed Advantage?

Acoustic designers routinely look for ways to smooth out sounds without bulking up acoustic foams. Micro perf’s intended job is to help tune lower frequencies without impacting high-end frequency absorption. At Technicon we sought to determine if the perforated films were able to tune, or if they simply reduced the structural integrity of the film.

What Is the Result?

Tests of normal incidence absorption comparing unperforated films with micro perf materials indicated little to no signs of effectiveness. Perforated material did not change absorption across the frequency spectrum. While the tests indicated some marginal changes, the changes would not alter the sound experience. Listeners would not be able to perceive audible differences.

During tests with random incidence absorption compared to micro perfs, testers found some material effects. Microperf created smoother sound absorption effects. But the cost of this modification was an overall higher frequency of sound. Unperforated material in the same random incidence environment led to similar results.

Another limitation of micro perf is its porosity. Covering acoustic foam with nonporous films — with no perforations —has several benefits, such as preventing oils and moisture from contaminating the foam. But the holes make micro perf porous.

In fact, the tests seem to indicate, micro perf just creates an additional expense with no added value, since micro perf is more expensive than non-perforated alternatives. The holes also allow substances like water, oil, and grease to damage the material. Perforations can also shorten the lifespan of acoustic foams by allowing UV radiation to degrade the material.

Contact Technicon Acoustics for More Sound Science Help

There’s no short cut to fixing absorption peaks and smoothing out sound. Instead, professionals need to be able to tune acoustic absorbers and find the right ratios between the foam’s composite layers.

Technicon Acoustics specializes in creating acoustic solutions that improve sound quality. Our products are designed to absorb, block, or isolate high- or low-frequency sounds. We have a team of expert sound engineers and scientists that research, design, and test high-quality sound shielding equipment.

You can order standard shielding and damping equipment or talk to our team about a customized solution just for your facility’s needs. We work hard to create the perfect order experience. This includes shipping the correct quantities and types of material on time for every order so our customers can confidently move forward with complex or time-sensitive projects.

Contact our team today or request a quote to start creating the optimal sound environment.

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.