Acoustic Modifications for the Classroom

1. Acoustic Modifications for the Classroom Angelea Kronlage, Au.D. Kristyn Tramel, Au.D.

2. Learning Objectives • Participants will be able to identify measures to improve the listening environment of students with hearing impairment. • Participants will gain an understanding of classroom design and how it impacts classroom acoustics and educational outcomes. • Participants will gain an understanding of what background noise is, how it is measured and what the ANSI standards are for signal-to-noise ratio in a classroom. • Participants will be able to identify specific physical and behavioral changes which may be applied to improve the listening environment and how these changes can be measured objectively.

3. Acoustic Accessibility Access to spoken information in a manner which minimizes acoustical barriers such as noise and reverberation. Why is this important? • The foundation of educational instruction is verbal communication • Noise causes students to miss 1/3 of spoken communication in class • Noise interferes with speech perception • Speech perception is necessary for auditory learning Source: Coalition for Classroom Acoustics

4. Impact of Poor Classroom Acoustics on Students • Academic difficulties • Communicative challenges • Negative impact on psychosocial development • Compromised psychoeducational performance Source: Deconde Johnson, C. and Seaton, J. (2012)

5. Student Populations at Risk for Learning & Listening Challenges in Classrooms with Poor Acoustics • Younger than age 13 • Conductive Hearing Loss • History of recurrent otitis media • Language or articulation disorder • Learning disability or dyslexia • English as a second language (ESL) • Auditory processing disorder • Minimal bilateral sensorineural hearing loss • Unilateral sensorineural hearing loss • Developmental delays • Attentional deficits • Cochlear Implants • Auditory neuropathy spectrum disorder (ANSD) Source: Deconde Johnson, C. and Seaton, J. (2012).

6. Minimal Hearing Loss in Children • unilateral sensorineural hearing loss – average air-conduction thresholds (.5, 1.0, 2.0 kHz) > 20 dB HL in the impaired ear and average air-conduction thresholds in the normal hearing ear < 15 dB HL; • bilateral sensorineural hearing loss – average pure tone thresholds between 20 and 40 dB HL bilaterally • high-frequency sensorineural hearing loss – air-conduction thresholds greater than 25 dB HL at two or more frequencies above 2 kHz (i.e., 3.0, 4.0, 6.0, or 8.0 kHz) in one or both ears • Prevalence of minimal hearing loss in children is between 4.5% - 12.5% Source: Tharpe, A. (2007)

7. Effects of Minimal Hearing Loss • When compared to normal hearing peers, children with minimal hearing loss exhibit the following difficulties on speech perception tasks in the presence of competing noise: • Overall poorer performance on speech perception tasks • Missing more high-frequency consonant information • Greater degree of degradation in performance as a function of less favorable signal-to-noise ratios • Higher degree of psychosocial or physical health problems • Lower performance on achievement tests • Retrospective studies have shown that 37% of students with minimal hearing loss repeated a grade compared with a 3% incidence for students with normal hearing. • Students with minimal hearing loss have an even greater risk in classrooms with poor acoustics Source: Tharpe, A. (2007)

8. Non-acoustic factors that affect speech recognition in the classroom: • Linguistic elements • Word/vocabulary familiarity • Context • Number of syllables in words • Linguistic competency of listener • Articulatory factors • Speaker gender • Speaker dialect • Speaker articulatory abilities Source: Deconde Johnson, C. and Seaton, J. (2012).

9. Acoustic factors that affect speech perception and learning in the classroom: • Background noise • Signal-to-noise ratio (SNR) • Reverberation time (RT) • Talker-Listener Distance • Interaction among acoustic variables can affect which information-carrying components of the speech signal are preserved. Source: Deconde Johnson, C. and Seaton, J. (2012).

10. Barrier: Background Noise Any auditory disturbance that interferes with what a listener wants or needs to hear. • Masks acoustic and linguistic cues • Weaker phonemes of speech such as transient consonant phonemes are particularly vulnerable and they carry 90% of acoustic information in speech. • Negative effects on attention, concentration, participation, behavior, academic performance

11. How is noise measured? • When we are measuring sound, we are measuing the amplitude of the soundwave, or how forceful the sound wave is. • Sound is measured in decibles or dB(A). 0 decibles is not the absence of sound, it is the average hearing threshold of the human ear. • Sound measurment tools: Noise dosimeter, sound level meter, integrating sound level meter

12. 120 dBA

13. When should you suspect that noise is a problem? • When the heating, venting, and air conditioning (HVAC) noise is clearly noticeable • When the teacher needs to turn off mechanical equipment when delivering important information or giving tests • When exterior noise (e.g., playground, traffic, construction) is constant • When sounds from adjacent rooms are clearly audible with the HVAC system turned off

14. Signal-to-Noise Ratio • Also known as SNR or S/N • It is the relationship or difference between the intensity level of the auditory signal (teacher’s voice) and the intensity level of the background noise • Ex: Speech signal of 70 dB SPL in a room with 55 dB SPL of noise = +15 dB SNR

15. Understanding SNR • Higher Signal-to-Noise Ratio = Better speech perception • If the teachers voice is above the background noise, then the SNR is a positive (+) number and it is a good listening situation. • If the teacher’s voice is quitter than the background noise, the SNR is a negative (-) number and it is a poor listening situation. Source: Smaldino, J. & Flexer, C. (2012)

16. SNR and Speech Perception • Adults with normal hearing do not see significant speech perception declines until SNR reaches zero (level of signal and noise equal). • Listeners with sensorineural hearing loss need SNRs of +4 to +12 for speech perception equal to that of listeners with normal hearing. • SNR of +15 or better is recommended for listeners with hearing loss and children.

17. Barrier: Reverberation • Persistence or prolongation of sound within an enclosed space (such as a room) as a result of sound waves reflecting from hard surfaces. • Degrades speech perception by masking directly transmitted sound. Signal energy that is reverberated in a room reaches a listener sometime after the direct sound energy. Spectral energy of vowels is prolonged and masks succeeding consonant phonemes, particularly world final consonant phonemes. Source: Deconde Johnson, C. and Seaton, J. (2012) John, A.

18. Reverberation Time • Reverberation time (RT): the amount of time it takes for a sound to decay in an enclosed space. • Rooms that are larger, have higher ceilings, are more oblong, and which have hard surfaces tend to have longer RT. • The most common acoustical measure of reverberation time is RT60, or the time it takes for an impulse sound to decay by 60 dB.

19. Typical Reverberation Times • Adults who have normal hearing, typically do not see compromises in speech perception until reverberation time of room exceeds about one second • Listeners that have sensorineural hearing loss need shorter reverberation times on the order of .4 to .5 of a second to achieve maximum performance. • Reverberation times that are considered to be optimal for children are the same as those for persons with hearing loss, about .4 to .5 seconds. • Audiometric test booths: 0.2 sec • Offices, living rooms: 0.4 - 0.8 sec • Classrooms: 0.4 – 1.3 sec • Auditoriums, gymnasiums, assembly halls: 3.0 – 4.0 sec

20. Barrier: Distance The distance from the sound source has a significant effect on the signal-to-noise ratio. • Direct sound level decreases in linear proportion to the distance between the talker and the listener. • There is a 6 dB decrease in sound pressure level with each successive doubling of distance from the sound source. • There is also an interaction between reverberation and distance. • As the talker-to-listener distance increases, reverberation dominates the listening environment. Source: Deconde Johnson, C. and Seaton, J. (2012). Smaldino, J. & Flexer, C. (2012)

21. Critical Distance The distance from a sound source at which the direct sound and reverberant sound are at equal levels (Smurzynski, 2007). • Listeners within the critical distance hear a signal that is clearer than those who are beyond the critical distance. • When a listener is at 1/3 of the critical distance, direct sound is at least 10 dB louder than the reverberant sound. • When listener is at a distance that is three times the critical distance, direct sound is reduced to a level at least 10 dB lower than reverberant. • Critical Distance is related to size and shape of a space as well as the absorbent characteristics of materials in that space. • In most rooms, the critical distance is somewhere between 2 and 6 meters (6.5 ft. – 20 ft.) from the speaker. Source: Deconde Johnson, C. and Seaton, J. (2012). Smaldino, J. & Flexer, C. (2012)

22. Impact of Poor Classroom Acoustics on Teachers • Vocal stress and fatigue • Stress related to additional effort to promote effective learning environment Sources: Deconde Johnson, C. and Seaton, J. (2012) Roy, N., Merrill, R., Thiebeault, S., Parsa, R, Gray, S., & Smith, E. (2004).

23. Impact of Poor Classroom Acoustics on Teachers • In a study conducted by Roy, et al. (2004), 43% of teachers reported the need to reduce classroom and communication activities because of vocal problems and 18% reported missing work each year because of voice related problems. Sources: Roy, N., Merrill, R., Thiebeault, S., Parsa, R, Gray, S., & Smith, E. (2004).

24. Classroom Acoustical Standards • In 1998, the United States Access Board determined that the acoustical environment is a key factor contributing to student learning, and acoustical barriers should be addressed in the classroom design phase. • On June 26, 2002, the ANSI/ASA S12.60-2002, Acoustical Performance Criteria, Design Requirements and Guidelines for Schools was approved and the Acoustical Society of America recently approved a revision to current standards which are referred to as ANSI/ASA (2010) or ANSI S12.60‐2010.

25. Classroom Acoustical Standards • The purpose of the classroom acoustics standard is to assist school planning and design professionals in providing learning environments that allow for good speech communication between teachers and students in the classroom and learning spaces without the use of electronic amplification devices. • The standard is voluntary unless referenced by a state code, ordinance, or regulation. • Many advocates hold the view that the standard is a civil rights issue and strive to include the standard in the Americans with Disabilities Act Accessibility Guidelines (ADAAG).

26. American National Standards Institute • The Institute oversees the creation and use of thousands of norms and guidelines that directly impact businesses in nearly every sector • The following classroom acoustic ANSI standards were established in collaboration with the Acoustical Society of America and a panel of experts

27. ANSI Standards: Background Noise Unoccupied classroom background noise levels must not exceed 35 dBA 35dBA

29. ANSI Standards: Background Noise The signal-to-noise ratio (the difference between the teacher's voice and the background noise) should be at least +15 dB

30. ANSI Standards: Reverberation Reflected sound is called reverberation. The time it takes for reflected sound to become inaudible is the reverberation time. The shorter the reverberation time, the better the speech intelligibility ANSI Standard: Reverberation time should be .6-.7 seconds, depending on the size of the clasroom

31. Barrier: Background Noise Solution: Reduction - • Windows • Install storm window • Replace old windows with more insulated units or sound reducing windows • Doors • Doors should be tight fighting with seals and gaskets • Special sound-control doors are available • Heating Ventalation and Air Conditioning • Custom built sound enclosure around the units • Appropriate ductwork

32. Barrier: Background Noise Solution: Reduction - Install chair footies made of felt and rubber bands. Tennis balls contain latex which may cause an alergic reaction. Tennis balls are also prone to mold. • Other sports balls and latex free materials

33. Barrier: Background Noise Solution: Reduction - Avoid open classrooms including temporary or sliding walls that separate instructional areas - Diminish the sound from computer keyboards by using rubber pads or carpets under the keyboards • Whenever possible, locate all computer equipment in a separate “computer/technology” room in the school. - Consider sound produced by motors, fans, air moving through the HVAC system, projectors, aquariums and hamster wheels

34. Barrier: ReverberationSolution: Increase Abosorption • Window coverings • Soft materials such as corkboard or felt on the walls • Hang children’s artwork or flags from the ceiling • Place rugs and carpets on the floor • Plants, paintings and soft furniture

36. Barrier: ReverberationSolution: Increase Abosorption Custom built sound absorbing classroom modifications

37. Barrier: ReverberationSolution: Increase Abosorption Traditional sound absorbing acoustic panels

38. Barrier: ReverberationSolution: Increase Abosorption Drop ceiling with added fabric

39. Barrier: ReverberationSolution: Increase Abosorption DIY acoustic panels made from foam. Old towels are also great for sound absorption

41. Barrier: Distance Solution: Seating Modifications • Preferential or flexible seating arrangements • Sitting in a horseshoe or circle during group activities. • Keep in mind children hear best on implanted side • Seated away from the window, heating/air unit  or noisy peers

42. Limitations of Hearing Aids and Cochlear Implants in the Classroom • Improves signal to noise ratio in noisy/reverberant environments • Noise suppression technology benefit is limited when background noise is actually other children in the class talking • Benefit of directional mics limited in reverberant environment

43. Cochlear Implant Simulation: • https://www.youtube.com/watch?v=SpKKYBkJ9Hw

44. Hearing Assistive Technology

45. Personal FM Systems • Frequency-modulated (FM) system uses radio waves to deliver the speech signals directly from the speaker to the listener • Two basic components: • FM transmitter: Picks up the speakers voice from the microphone and sends the signal via radio waves the the FM receiver • Receiver: Recieves the signal from the transmitter when both devices are one the same channel. Can connect to a hearing aid, cochlear implant or by itself. Personal FM systems increase the S/N ratio 20-30dB

46. Personal FM Systems Personal FM systems increase the S/N ratio 20-30dB

48. Soundfield Amplification/ Sound Distribution • The teacher’s voice is transmitted from a wireless microphone (worn as a headset, on the lapel, or passed around the class) to speakers mounted around the classroom Soundfield systems increase the speakers conversational voice to 60-65dBA

49. Soundfield and FM Systems for children without hearing loss • Children with normal hearing can also benefit from an improved signal to noise ratio • Especially helpful for children already at risk of academic challenges

50. Induction Loops • An induction loop system transmits an audio signal directly into a hearing aid via a magnetic field. • An induction loop wire is permanently installed in the floor or ceiling and connects to a microphone used by a speaker. • The person talking into the microphone generates a current in the wire, which creates an electromagnetic field in the room. • This is the ‘T-coil’ setting on a hearing aid