Their choices in flooring can make any area more conducive to learning and information retention. Therefore, careful consideration should be taken when considering flooring choices in an educational setting.
In today's academic environment, students are confronted with a variety of unwanted or unpleasant sounds, which is essentially noise. Both loud disruptive noises, such as intercom systems and alarms, as well as background or low-level noises such as the hum of an air conditioner or doors closing, can affect attention, understanding, overall academic performance and even student health. According to the National Institute for Occupational Safety and Health, ambient noise can even increase general stress levels and aggravate stress-related health conditions, including high blood pressure and migraine headaches. Additionally, teachers and professors needing to raise their voices in loud or reverberant classrooms may experience greater stress and fatigue.
Various commercial floor coverings such as rubber, resilient/vinyl, carpet and textile composite flooring control sound differently. Harder materials such as rubber and resilient/vinyl absorb little or no sound and have greater potential to transmit sound, contributing to a noisier learning environment. Softer materials such as carpet and textile composite flooring-a high-performance product constructed of knitted polyester fabric and cushioned polyester felt backing that is an effective alternative to hard-surface flooring-absorb significantly more sound and transmit less sound, contributing to a quieter academic setting. In fact, the study "Evidence-Based Design in Schools: Classroom Design and Academic Achievement" found that students in classrooms with carpet scored higher on tests in math, language and other subjects than students in classrooms with hard floor coverings.
NOISE AND SPEECH INTELLIGIBILITY IN THE CLASSROOM
The traditional American university teaching style primarily involves speech-related activity, such as an instructor lecturing the class. However, high noise and reverberation levels, which are common in many university classrooms, tend to hinder speech intelligibility, causing reduced understanding and ultimately reduced learning.
In fact, according to researchers at the University of Minnesota, many U.S. classrooms have a speech intelligibility rating of 75 percent or less. Speech intelligibility, or speech recognition, is the degree to which speech can be understood. The Acoustical Society of America recommends 95 percent speech recognition for effective learning in schools. This means listeners with normal hearing can understand 95 percent of the words read from a list.
As speaking volume approaches that of background noise, speech recognition declines dramatically. When speaking volume equals the background noise, a person achieves just 40 percent speech recognition. A person must speak 12 decibels (dB) louder than the ambient noise to achieve 95 percent speech recognition.
Excessive reverberation, the continuing effects of a sound, also interferes with speech intelligibility. Like echoes, they occur when sound waves strike a surface and are reflected back into the space. Shorter reverberation times aid speech recognition. For example, the recommended reverberation times for classrooms are 0.4-0.6 seconds. To reduce reverberation time, sound absorption must be increased or noise volume decreased.
Flooring choices can help speech recognition in the classroom. Test results show that soft surfaces mute noise by absorbing reverberation. In one study, reverberation times of a handclap and human speech in an empty room with a hard, concrete floor were measured at 3.3 seconds. Measurements were taken again after carpet was installed in the space and the reverberation time was shortened to 1.6 seconds, a significant difference.
ACOUSTIC PROPERTIES TO CONSIDER WHEN SPECIFYING FLOORING
Independent laboratory tests show carpet and textile flooring control noise more effectively than any other floor covering. The two most important acoustical factors to consider when specifying flooring are the product's sound absorption and noise reduction capabilities. Laboratories typically use two tests to measure the acoustic properties of interior surfaces and finishes: airborne noise reduction and structure-borne noise reduction.
AIRBORNE NOISE REDUCTION
The typical frequency range for normal human hearing is 100-10,000 Hz. The human voice falls within the low-frequency end of the spectrum, at around 100 Hz. Building noises such as those emanating from elevators, HVAC systems and mechanical systems fall near the 1,000 Hz range. Loud noises such as alarms and bells are in the high-frequency end, up to 10,000 Hz.
The airborne noise reduction test, ASTM C423-02a, measures a surface's ability to absorb these and other airborne sounds which contribute to ambient (background) noise. The test measures the product's absorption of sound at 15 different frequencies that fall within the range of what a normal human ear can hear.
A floor covering's measure of effectiveness in absorbing airborne sound is expressed as a Noise Reduction Coefficient (NRC). The greater the absorption, the higher the NRC number. A surface that completely eliminates sound has an NRC of 1.0. Hard surfaces such as rubber and vinyl typically have NRCs of about 0.0-0.015. In other words, they absorb little to no airborne sound. Commercial carpets used in schools have NRCs typically ranging between .15 and .2, meaning they absorb about 15-20 percent of airborne sound. A textile composite flooring's NRC is about .30, signifying 30 percent sound absorption.
STRUCTURE-BORNE NOISE REDUCTION
Structure-borne noise reduction tests study the material's ability to reduce impact sound transmission into the space below. Footsteps and objects dropping on the floor are examples of impact noises. This test is important to perform on flooring materials selected for multi-level school buildings.
The structure-borne noise reduction test most used for flooring, ASTM E492-09, is performed using a tapping machine in which five hammers strike the floor 10 times per second. Sound pressure in 16 frequency bands is measured in a reverberation room below the floor being tested. The measure is expressed as a whole number, Impact Insulation Class (IIC). The higher the numerical rating, the greater the sound insulation.
ICC ratings vary, depending on materials and construction. IICs for vinyl typically range from 15 to 20. The results for rubber range from 15 to 30. Carpet IICs range from 35 to 50. The IIC for textile composite flooring is 64.
Clearly, all types of flooring, hard and soft, have merit and should be considered based on the requirements of the space. By realizing the role a flooring product can play in acoustical control and noise reduction, university facility managers can create effective and healthier learning environments, which translates into positive results for their school, students and teachers.
Photography provided by J+J Flooring Group
is the director of business development for education and healthcare with J+J Flooring Group. With more than 30 years experience in the commercial flooring industry, he provides leadership and market direction for new product development and marketing strategies for the company's education and healthcare segments.