Room Acoustics


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Room Acoustics

  1. 1. Room Acoustics Importance of hearing/listening <ul><li>Approximately 45% of school time spent listening </li></ul><ul><li>Approximately 30% speaking </li></ul><ul><li>Approximately 16% reading </li></ul><ul><li>Approximately 9% writing </li></ul>
  2. 2. Listening <ul><li>Detection </li></ul><ul><li>Discrimination </li></ul><ul><li>Recognition </li></ul><ul><li>Comprehension </li></ul>
  3. 3. Room Acoustics <ul><li>Room noise </li></ul><ul><li>Room reverberation </li></ul><ul><li>Talker-listener distance </li></ul>
  4. 5. What happens to sound when it hits a barrier? <ul><li>Absorbed </li></ul><ul><li>Reflected </li></ul><ul><li>Transmitted (pass through) </li></ul><ul><li>Diffracted </li></ul>
  5. 6. Hitting a barrier
  6. 7. What is reverberation? <ul><li>Reflected sound off surfaces (repeatedly) </li></ul><ul><li>Causes prolongation of sound </li></ul><ul><li>Longer the reverberation the more “smear” of speech sounds </li></ul>
  7. 8. Reverberating environments
  8. 9. Reverberation <ul><li>Vowels tend to smear consonants because: </li></ul><ul><ul><li>More intense </li></ul></ul><ul><ul><li>Higher frequencies of consonants are absorbed more effectively by room surfaces </li></ul></ul>
  9. 10. Reverberation time <ul><li>Time it takes a sound to stop reflecting </li></ul><ul><li>Reverberation time (RT) is the time in seconds for a sound to reduce 60 dB in intensity once the generation of sound has stopped </li></ul><ul><li>Hard room, long RT time </li></ul><ul><li>RT of room alters the effect of the speaker-listener distance upon sound intensity </li></ul>
  10. 11. 28% 48% 0 52% 71% +6 60% words correct 83% words correct +12 .04 Hard of Hearing Normal S/N RT in sec
  11. 12. 11% 30% 0 28% 54% +6 41% 70% +12 1.2 Hard of hearing Normal hearing S/N RT in sec
  12. 13. Noise <ul><li>Acoustical noise is any unwanted sound </li></ul><ul><li>Noise floor </li></ul><ul><li>Signal </li></ul><ul><li>Signal to noise ratio (S/N) </li></ul><ul><li>Optimal S/N are 30+dB for HOH and 20+dB for normal hearing students </li></ul>
  13. 14. What are sources of sound in classroom? <ul><li>External </li></ul><ul><li>Internal </li></ul>
  14. 16. Acoustic barriers <ul><li>Internal noise </li></ul><ul><li>External classroom noise </li></ul><ul><li>Reverberation </li></ul><ul><li>Speaker-listener distance </li></ul><ul><li>Poor acoustical treatments in classroom </li></ul>
  15. 17. <ul><li>Maximum learning to occur in educational environment- teacher’s voice MUST be highly intelligible to all children </li></ul><ul><li>For pediatric listeners, signal must be approx 10dB louder than background noise </li></ul>
  16. 18. Speech intelligibility ratings <ul><li>One study stated that many classrooms have a rating of 75% or less. </li></ul><ul><li>It is pointed __ that this is ___ to reading a ___ in which every ___ word has been ____. </li></ul><ul><li>Difficult for children with limited vocabularies, leaning disabilities, auditory processing problems, and English is a second language </li></ul>
  17. 19. How to reduce noise
  18. 20. New ANSI/ASA standards <ul><li>1999 two boards partnered on development of new standards for acoustics in classrooms (takes into account children with hearing loss) </li></ul><ul><li>Standard completed in 2002 (Acoustical Performance Criteria, Design Requirements and Guidelines for Schools) </li></ul>
  19. 21. <ul><li>Specific criteria for maximum background noise (35 dB) </li></ul><ul><li>Reverberation (0.6-0.7 for unoccupied classroom) </li></ul><ul><li>Compliance is voluntary </li></ul><ul><li>May need for new schools </li></ul><ul><li>Parents find standard useful for accommodations under IDEA </li></ul>
  20. 22. <ul><li>One study should that unoccupied classroom noise levels (M=47.48 dB) exceeded standard of 35 dB for 96.67% of classrooms in 1994 study </li></ul><ul><li>Unoccupied classroom noise levels and acoustical treatments in elementary classrooms have not changed over the past decade </li></ul>
  21. 23. Benefits of FM systems for students (Classroom) <ul><li>Improvement in academic achievement </li></ul><ul><li>Improvement in speech recognition </li></ul><ul><li>Improvement in attending and learning behaviors </li></ul><ul><li>Increased seating options for students with hearing loss </li></ul><ul><li>Improvement in listening and learning environments for “at task” learners (severely language impaired, DD, ESOL, minimally hearing impaired, etc) </li></ul><ul><li>Increased self esteem </li></ul>
  22. 24. Benefits for teachers <ul><li>Reduced vocal strain and voice fatigue </li></ul><ul><li>Increased ease of teaching </li></ul><ul><li>Increased versatility of instructional techniques </li></ul><ul><li>Increased teacher mobility </li></ul>
  23. 25. 1994 Project report <ul><li>Evaluations were completed by 1221 students </li></ul><ul><li>55 gen ed teachers </li></ul><ul><li>630 parents </li></ul><ul><li>27 school administrators </li></ul>
  24. 26. <ul><li>More than 95% if students agreed that the /fm system made it easier for them to hear their teacher, help them listen better, and helped them hear when teacher was writing on the board </li></ul><ul><li>92% agreed that they wanted to use the FM system in their class again the following year </li></ul>
  25. 27. <ul><li>Classroom teachers unanimously identified a decrease in vocal strain as the foremost benefit from using FM sound-field amplification </li></ul><ul><li>100% agreement that the FM system enabled their voice to reach all students </li></ul><ul><li>96% agreement that students’ behaviors related to attentiveness, listening, and comprehension seemed to improve when using the FM soundfield </li></ul>
  26. 28. <ul><li>Parents were in at least 46% agreement that their child’s grades improved when using the system </li></ul><ul><li>44% agreed that their child’s behavior improved at school when the system was in use </li></ul>
  27. 29. <ul><li>School administrators were in 92% agreement that the FM system enhanced class instruction and management </li></ul><ul><li>53% agreement that there was a decrease in the number of behavior referrals from amplified classes </li></ul>
  28. 30. Resources <ul><li>Pilot Studies of Speech Communication In Elementary School Classrooms, Carl C. Crandell, University of Florida et al. </li></ul><ul><li>Revisiting Speech Interference in Classrooms and Considering Some Possible Solutions, Michel Picard, University of Montreal et al. </li></ul><ul><li>  America's Need for Standards and Guidelines to Ensure Satisfactory Classroom Acoustics, David Lubman, David Lubman and Associates. </li></ul><ul><li>  Impact of Hearing Loss on Children in Typical School Environments, Peggy Nelson, University of Maryland School of Medicine. </li></ul><ul><li>Classroom Amplification: Not Just for the Hearing Impaired Anymore, Lori Hubble Dahlquist, Children's Care Hospital and School, Sioux Falls, SD. </li></ul><ul><li>New Standards Should Help Schools in Noisy Classrooms, Dianne Weaver Dunne, Education World (School Administrators Article) - Online </li></ul><ul><li>  </li></ul><ul><li>  Want more? </li></ul><ul><li>Acoustical Society of America – Publications on Classroom Acoustics:                                         </li></ul><ul><li>Visit the National Clearinghouse for Educational Facilities (NCEF) at: </li></ul><ul><li>Need resources for hearing handicapped students? Try the Deaf Resource Center at: </li></ul><ul><li>  </li></ul>
  29. 31.