Editor’s Note: In September 1996, educational audiologist Karen Anderson, PhD, published in HR a brief article entitled “Thirteen Facts on the Impact of Hearing Loss on Education.” The article ended up being widely distributed and appeared in several audiology-related journals and newsletters (to obtain the article, click on the link at the end of the Internet version of this article at www.hearingreview.com). Eight years later, HR asked Anderson and Blumsack to write another “13 facts”—this time specifically addressing classroom listening.

Children on the road to learning need more than just a qualified teacher and a willingness to learn. Learning is about communication: ideas, facts, stories, skills, and much more. We learn through our senses, primarily through hearing and vision. Children cannot access classroom instruction unless they can clearly hear and see the teacher.

Every classroom has lights that allow the children to see the teacher, but relatively few classrooms have listening conditions that allow children to hear the teacher’s voice without interference and signal degradation. Listening is a main highway to learning. The facts below address hearing-related issues that are important for this successful journey.

1. Age has its privileges!
Children require quieter classrooms to be able to understand information as precisely as adults. Children under the age of 13 cannot process speech in background noise like adults can.1-7 Young children also do not have the mature language skills to expertly fill in the blanks when an ending, new word, or brief phrase is missed.

2. Loud enough is not Good enough
Almost 30% of classrooms are judged to be too noisy by educators.8 In a noisy classroom, teachers are at 20 times the risk (compared to average workers) of permanently damaging their vocal mechanisms.9,10 The average teacher takes at least 1 sick day a year related to vocal strain (think of the cost of substitute teachers!).11,12 What’s worse, raising your voice doesn’t work! When you raise your voice, the louder and longer vowel sounds are heard more clearly, but the consonants stay weak (you cannot yell an /f/ or /s/ sound successfully).1,13-15 Additionally, we need to hear consonant sounds to tell the difference between words (eg, the difference between “cat,” “cap,” “cast,” or “calf”).

3. “Close enough” is closer than you think
Children in the ideal listening range are at a distinct advantage when it comes to listening in a noisy environment. This range usually means listening within about 6 feet of the teacher’s mouth.16,17 Sound degrades over distance.18,19 Ever try to be understood across a street or in a large group at a busy restaurant? The same sound degradation in the classroom is subtle but very real. Listening takes work in noise and across distances.

It is no surprise that students in the back half of the classroom are usually not as engaged or do not seem to be learning as actively as those in the front. Preferential seating is not practical18 as classrooms are active; most teachers roam between rows and discussions occur between students. Communication across distance is part of everyday learning situations!

4. All noise is not equal
Any noise that has language content will interfere with understanding verbal instruction.3,20 Noise sources, such as a teacher’s voice from an adjacent class, talking from the hall, quiet voices, or a book on tape from the back of the room, are much more difficult for listeners to ignore than a quiet hum.

5. Learning problems are compounded by poor acoustics
Children with learning disabilities, attention deficit disorder, and other types of learning problems are significantly more affected by a poor listening environment than average and above average learners.21 Poor readers are not as able as good readers to extract the relevant bits of speech when listening in a typically noisy classroom environment. Students who need the most individualized assistance also require an appropriate listening environment to be able to learn optimally from instruction.

6. Quiet hum vs whoosh
All classrooms must be ventilated. Air moving about is essential for health and comfort. However, the heating, ventilation, and air conditioning (or HVAC) systems in schools are often the biggest culprits in creating classrooms that are too noisy. Due to value engineering and cost cutting measures needed to build schools for the children of baby boomers, many of our newest schools have louder HVAC systems than schools of the previous generation or before.

Whether the interference is from Mrs. Smith’s history lesson from the next room or the whoosh of the ventilator, background noise can mask the quiet, critical sounds of speech, like the /s/ that signals plurals, possessives, and more. Many teachers struggle with on-again-off-again air whooshing while their students are squirming and teachable moments are being lost. Although air moving is important, the purpose of school is to educate children, and the HVAC system should not act as a barrier to this goal for any student or teacher.18

7. Sound bouncing is not a game
Even in classrooms where there is very little interference from background noise, it is still possible for listeners to have difficulty understanding the teacher.7,22-24 This difficulty is caused by reverberation (or sound bouncing off of hard surfaces in a room). Reverberation is most noticeable in a gymnasium or cafeteria, but it is also very real in many, if not most, classrooms. A kindergarten classroom with vinyl floors, shiny desks, bright window, and a white board can be a reverberation nightmare!

Reverberation causes the longer vowel sounds to bounce back and cover up short consonant sounds, thereby smearing speech and destroying clarity. Reverberation that is slightly challenging for adults will cause major interference to listening and attention for young children. The effects of smeared speech increase with distance, and those who suffer most from this problem are children.25-27

Classroom Size Avg Background Noise (A-Weighted, 1-hour avg.) Maximum   Reverberation Time (avg reverberation at  500 Hz, 1 kHz, 2 kHz)
< 10,000 ft3 (typical classroom with ceilings < 10ft) 35 dB SPL 0.6 seconds
>10,000 ft3 to <20,000ft3 (equivalent to about 2 typical classrooms) 35 dB SPL 0.7 seconds
>20,000 ft3 (cafeteria, corridor, gymnasium) 40dB SPL (45 dB SPL if not a structured learning space) Sound-absorbing materials equivalent to 50-75% of the ceiling area
Table 1. Summary of standards for how noisy a classroom can be before childrens’ hearing will be adversely affected. Adapted from Sutherland & Lubman (2004).44

8. The devastating duo
Excessive background noise and reverberation work together as a one-two-punch to speech understanding. In combination, they are much worse than if either condition occurred alone.22,28-34 These invisible villains can have an insidious effect on student learning and school test scores. As of 2002, there are national standards (Table 1) for just how noisy and reverberant a classroom can be before children’s learning will be affected.

9. One reason Johnny can’t read
Children educated in noisy classroom conditions perceive speech less clearly, have greater difficulties with auditory discrimination, and have lower reading scores. In cases where acoustic treatment was provided and the noise level in the classroom was reduced to appropriate levels, reading test scores significantly improved. Chronic noise exposure is linked to reading deficits, regardless of the level of parent education or family socioeconomic status.35-39

10. When it’s noisy, they tune out…not in
Learning is all about being presented with new and challenging information and having to problem-solve and apply new information appropriately. A child who gives up easily in frustration when presented with new information will not become the successful learner needed in the 21st century. Children educated in noisy classrooms give up trying to solve problems sooner than children educated in acoustically appropriate classrooms.36 When required to listen in noise for long periods of time, children become less motivated to put forth the energy required to listen, and they have less energy to devote to processing the information. Thus, when noise is present, the ability to perform complex tasks can be significantly affected.40 Children don’t get better at listening in noisy classroom conditions: they don’t learn to tune in, they tune out, or they struggle.

11. ESOL also stands for “Excellent Sound Optimizes Learning”
When the teacher speaks a language different from the student’s native language, special listening problems occur.41 In studies that measured how precisely individuals are able to listen in noisy and reverberant conditions, those who were English as a second language (ESOL) learners had speech perception similar to listeners with hearing loss. Listening is much more difficult if the language is not yours and the sounds are smeared and obscured by reverberation and noise.

12. Consider potential hearing loss for any child
Medically, a child is not considered to have abnormal hearing until his/her hearing loss reaches 25 dbHL. A 25 dB hearing loss is only slightly worse than plugging your ears with your fingers!42 Schools are often screened at 20-25 dBHL.

The typical ear infection causes a “plugged ear” hearing loss. Two-in-three pre-schoolers have been shown to have at least 1 episode of ear problems, and 1-in- 6 preschoolers (16%) have 6 or more episodes. Half of these episodes go undetected by parents and teachers. Even with good medical follow-up, 10% of preschoolers continue to have chronic ear problems during critical language development years.42,43

Any hearing loss is too much hearing loss in a noisy room. Listening at a distance, masking of speech due to noise, and smearing of speech due to reverberation all have devastating effects on the speech perception of the child with hearing loss.22,32,33

Hearing aids do not have a magical ability to help a child hear through background noise; hearing aids amplify all classroom sounds (both wanted and unwanted). In other words, the sounds from verbal instruction and background noise are all amplified. Only hearing technology in which the teacher wears a microphone and her amplified voice goes directly to the child’s hearing aids, cochlear implant, or a desktop speaker can help to overcome speech perception problems in background noise.44 This has recently been confirmed by Anderson, Goldstein, Colodzin & Inglehart (unpublished data, 2003).

Are loudspeakers the answer? Not if there is excessive reverberation. Amplification that is delivered through speakers on the walls or in the ceiling typically does not help students with hearing aids or a cochlear implant much beyond the help they get from their personal devices alone. The amplified sound from loudspeakers still is degraded across distance, and so the advantages of having speakers in the classroom are essentially lost to the student with hearing impairment. In some cases where classrooms are highly reverberant, loudspeakers on the walls can actually cause greater smearing of speech and listening problems to all children, especially those using amplification devices.

13. How good is good enough?
Children listen best when the teacher’s voice is 15 dB louder than background noise and when reverberation is low.45 Today’s students need to be able to discuss in small groups and work cooperatively as part of an interactive and dynamic school curriculum. National standards now specify how good is good enough (Acoustical Society of America/ANSI standard [S12.60-2002])46 and should guide the design of new and remodeled schools.47 Sound should not leak through from adjacent classrooms, halls, and playgrounds, and hard surfaces should be softened when possible. Good thick acoustic tile will be the biggest help to reduce reverberation, and carpet can be a big help, too. Background noise sources like the heating and air conditioning systems need to be identified and addressed. Even costly changes are a bargain compared to the price of lost learning.48

Judith T. Blumsack, PhD, is an assistant professor at Auburn University, Auburn, Ala. Karen L. Anderson, PhD, is a coordinator of hearing services at the Florida Department of Health. She helped develop the 2002 ANSI standard for acoustical performance in schools.

Correspondence can be addressed to HR or Karen Anderson, PhD, email: [email protected].

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