2. Using Group Amplification in the Classroom by Pamela Schlitt Ana Paula G. Souza Sabrina Strudwick

3. I. Benefits of Using FM Systems and Sound Field Systems in the Classroom  To Students with Hearing Loss  To Students without Hearing Loss  To Teachers

4. Basic Rationale FM systems and sound field systems are used to improve the signal to noise ratio by increasing the speech input level.

5. A Signal to Noise Ratio  The signal to noise ratio is the difference between the signal level and the noise level in the classroom.  The teacher’s voice is an example of a signal.  An example of a noise would be air conditioners, background voices, traffic, etc.

6.  In a typical classroom, the teacher’s voice is 65 dB SPL, and the noise level is 60 dB SPL.  Therefore, the signal to noise ratio is +5 dB. (65/60=5)  Many hearing impaired students need a 20+ dB signal to noise ration.  FM and sound field systems reduce the effects of noise, making it easier for students to understand the teacher and improve academic performance.

7. Advantages of FM Systems  Individual to the child  Can be used with the child’s hearing aid  Easily transportable  Saves the teacher’s voice  Can be adjusted to maximize the signal in different environments (lecture, group discussion, etc.)

8. Enjoying our FM Systems!

9. Advantages of Sound Field Systems  Cost - One system is less expensive than a special education class for a child.  Benefits all children including normal hearing children with ADD, learning disabilities, and children with mild or fluctuating hearing loss  Removes stigma of “hearing loss” from child

10.  Lower maintenance for children  Teacher acceptance- saves the teacher’s voice  Teaches good communication skills during the class (Use microphone one at a time to speak)

11. Sound Field System

12. II. Speech Acoustics

13. The average conversation level is 40-80 dB HL. To better understand that range, take a look at loudness levels of common sounds.  Whisper30dB  Type writer 70dB  Food Blender90dB  Train 100dB  Chain Saw 110dB  Jet 120dB

14. Just as these different environmental sounds have varying loudness levels, so do individual sounds of our language.  Vowels, nasal consonants (consonants made with the vocal tract-m, n, ng), and most voiced consonants (those consonants that require the vocal folds to vibrate- such as b, d, g, z, v, j) are louder than voiceless consonants (such as f, s, th, k, sh, ch, p).

15. However, not only do sounds of the English language vary by loudness, they also vary according to pitch.  Vowels, nasal consonants, and most voiced consonants are in the low pitch range.  Voiceless consonants are in the high pitch range.

16. These varying levels of loudness and pitch in the English language affect the child with a hearing impairment’s ability to hear and understand all of the speech signal being presented.  The sounds with low loudness levels and high pitch levels may be especially difficult for children with a hearing impairment to hear.

17. Varying Degrees of Hearing Loss and the Effects on Understanding Language and Speech  Children with minimal or borderline hearing losses (16-25 dB HL) can miss up to 10% of the speech signal if the teacher is more than 3 feet away or if the classroom is noisy.  These children may appear inappropriate, awkward, or immature.

18.  Children with mild losses (26-40dB HL) can miss from 25-50% of the speech signal. Without amplification, the child with a high pitched hearing loss may miss consonant sounds.  These children seem as if they are “day dreaming” or “not paying attention” and cannot block out background noise.

19.  Children with moderate loss of 40 dB HL may miss 50-75% of the speech signal. Children with a 50 dB HL loss may miss 80-100% of the speech signal.  These children are likely to have limited vocabulary, delayed or defective syntax, imperfect speech production, and an atonal voice quality.

20.  Children with moderate to severe losses (65-70 dB HL), severe losses (71-90 dB HL), or profound losses (91 dB or more) can miss 100% of the speech signal without amplification.

21.  Children with unilateral hearing losses (one normal ear and one ear with at least a permanent mild loss) may have difficulty hearing faint or distant speech. They will also have difficulty hearing in noisy environments.  These children may be accused of “selective hearing” and may appear inattentive or frustrated and present with behavior problems.

22. One can see from the previous examples, the importance of improving the signal to noise ratio for children with varying degrees of hearing loss to improve their academic performance and social functioning in the classroom.

23. III. FM Auditory Training Systems Individual FM Systems Sound Field FM Systems

24. Standard Parts of FM Systems  Microphone - picks up sound in acoustic environment and converts it to electrical signal  Transmitter - worn by teacher; uses the electrical signal to modulate the frequency of a high frequency carrier signal, which is then broadcast via an antenna  Receiver - worn by child; demodulates the frequency-modulated signal, which is then amplified and delivered to the user  Transducer - modifies the frequency response from the receiver

26. Types of Individual FM Systems  Basic  Button earphone delivers sound to child  Personal  Sound coupled to the personal hearing aid (HA) via direct-input, silhouette, or neckloop  Ear level  FM receiver is in behind-the-ear (BTE) case which also works as a HA  Boot  FM receiver is in boot that snaps onto BTE HA

27. FM Transmitter Options  Microphones  Omnidirectional - picks up sound from all directions  Directional - distinguished by openings around the sides, which allow for a reduction in amplification of sounds impinging on the sides relative to sounds impinging on the top  Boom - worn with a headband or clipped to eyeglasses so that the microphone is approximately two inches from the lips and moves with the head  Pass Around

28. Teacher wearing an FM transmitter with a lapel microphone clipped on the shirt

29. Teacher wearing a Boom Microphone

30.  Transmitter Frequencies  Fixed Frequency - one of 40 narrow frequency bands between 72 and 76 mHz that are number/letter or color-coded  Variable Frequency - dial in channels or removable oscillator

31.  Alternate Signal Inputs  Audio In Jack - used to hook up transmitter to tape recorder or video player  Microphone Jack  Mic + Audio Switch - allows the teacher’s voice to be transmitted along with the auxiliary audio source

32.  Transmitter Controls  No FM Light - indicates that the microphone has not been plugged in correctly or there is a problem with the microphone cord  Low Battery Light - only informative if the light is on because it goes not illuminate when the battery is completely exhausted  Automatic Gain Control Adjustment - used to vary the loudness level of the input signal at which the reduction in gain begins

33. FM Receiver Options  Microphones  Monaural Omnidirectional - one microphone port  Dual Omnidirectional - two microphone ports  Dual Directional - two ports on the front and one on each side so that sounds impinging on the front are amplified to a lesser degree than those impinging on the side  Behind-the-ear - ports by the earhooks; allows for a closer approximation of binaural hearing, environmental microphones on the receiver case must be deactivated  Pass Around- may be plugged into an audio-input jack on the receiver

34.  Receiver Frequencies  Single Channel - number/letter or color-coded  Dual Channel  Internal/External Oscillator - general frequency is internal and class/specific frequency is removable

35.  Input/Output Connections  Audio In Jack  Audio Out Jack - to another audio source such as a tape recorder  Pass Around Microphone

36.  Receiver Controls  FM signal only, FM + Environmental signal together, or Environmental signal only  SSPL90, Tone FM Ratio, Right/Left Ratio, Gain  Environmental Microphone  Volume  No FM Light  Low Battery Light

37.  Coupling Methods  Headphone or Stetoclip - for persons with auditory processing problems but normal hearing  Bone Oscillator - for persons with malformed ear canals or draining ears  Button Earphones - allow for the greatest power  Behind-the-Ear - microphone, amplifier, receiver, battery, and oscillator contained in the BTE case  Personal Hearing Aid via:  direct-input - electrical signal from FM receiver led directly into HA via a boot or audio-shoe connection  silhouette - requires a HA with a T-coil and an electromagnetic field is created in a wafer-shaped piece worn between the head and the HA  neckloop - electrical signal from FM receiver delivered to neckloop that creates an electromagnetic signal which is picked up by the T-coil of the HA and amplified

38. Button receiver Direct input receivers

39. Behind-the-Ear FM Receiver

40. Direct Input- FM Receiver coupled with the hearing aid

41. FM Receiver completely located in the “shoe” which would be attached to the hearing aid

42. Student wearing a neckloop arrangement

43. FM Battery Options  Batteries  Removable Nicad Battery Pack - packs may stay on the transmitter or receiver during charging or can be removed and charged separately; charge lasts 18-25 hours  Removable Nicad Battery (9 or 3-volt) - batteries remain in the units during charging; charge lasts 7-14 hours  Removable Alkaline (9-volt or two 1.5-volt) - charge last 15-20 hours

44.  Charging Units  Case charger - spaces for 12 units, charging time is 8-12 hours  Modular charger - two-pocket charger used for a transmitter and receiver pair; can be expanded by adding on sections to charge up to 12 units  Wall charger - charges a transmitter/receiver pair; plugs are connected to the units and the charging unit is plugged into a standard wall socket

45. Ideal Transmitter  Variable transmitting channels for maximum flexibility in case other signals interfere  Audio input with talkover option so the teacher can provide input during a video, etc.  Boom directional microphone for a consistent signal as the head turns  Low Battery Lights  No FM Lights

46. Ideal Receiver  Dual Channel Oscillator for flexibility in case other signals interfere  Input/Out jacks  Options for FM, FM + ENV, ENV so that the student may receive the best possible S/N ratio relative to the instructional task such as class discussion or lecture  Direct-input coupling because internal noise is lowest, the signal is most consistent, and the child may wear his or her hearing aid all day  Low Battery Lights  No FM Lights

47. Ideal Battery  Operate on Nicad or Alkaline so that the user is not dependent on electrical sources for chargers  Modular charger with auto off

48. Sound Field FM Systems  Components  Microphone - worn by the teacher  Transmitter - worn by the teacher  Base Receiver  Amplifier  Speakers - send the signal throughout the room  Sound field systems vary by how many speakers are in the room, where they are placed, whether a pass around microphone is used for class discussion  Once again, sound field systems are important because they can benefit all children in the classroom

49. Sound Field System

50. IV. Room Acoustics

51. Things that affect room acoustics  Room Noise  Reverberation  Distance

52. Room Noise  is considered any undesirable noise in the classroom that may affect listening.  Even in an unoccupied classroom, there is background noise.  When occupied, background noise in the classroom increases.

53. Factors that cause room noise  Inside the classroom:  projectors  computers  fluorescent lights  fans, air conditioner  fish tanks, animals  chairs sliding on floor  clocks

54.  Outside the classroom:  noisy streets  hallways  music rooms  gymnasiums  auditoriums  lawn services

55. Measuring Noise  Noise can be measured using a sound level meter. This meter has a scale that relates to the same sensitivity curve as the human ear.

56. Studies have been done to measure noise in decibels for activities occurring in representative classrooms in Dallas and Chicago areas.  Noise in a carpeted class for hearing impaired children in a mainstream environment with 15 students and 2 teachers is about 59dB HL.  A normal teacher speaks at about 65 dB HL.  This gives us a signal to noise ratio of +6dB which is not adequate for hearing impaired students.

57. Ways to Reduce Classroom Noise  Cover bottom of chairs, desks, and tables with tennis balls to keep them from sliding on floors.  Choose a classroom away from external noises.  Keep windows and doors closed.  Place rubber strip around door to keep out hallway noise.

58.  Have noise rules in the classroom  use “inside voices”  only sharpen pencils at certain times  don’t slam books down  take “marshmallow” steps

59.  No fans  Avoid fish tanks and animal cages  Turn off computers when not in use  Seat hearing impaired students in front of classroom near the teacher and away from internal and external noises.

60. Reverberation  When sound leaves a source it travels in sound waves.  Sound waves may deliver direct sound before they come into contact with a boundary.  Once sound waves collide with a boundary, they are reflected.  Reverberation is sound reflected in the room after the source has stopped producing sound waves.

61.  Both direct sound and reverberated sound reach the listener.  The reverberated sound interferes with listening to the direct sound.  Reverberation can be measured by how long it takes a sound to stop reflecting.

62. Reverberation time can be measured using a reverberation meter or calculated manually by using measurements of the classroom and absorption coefficients from a table.

63. Important Things to Think About When Choosing a Classroom for Hearing Impaired Children  Ideal reverberation time is 0 seconds.  Recommended reverberation time for a classroom with hearing impaired children is 0.3 seconds.  Recommended reverberation time for a classroom with normal hearing children is 0.5 seconds.

64.  Rooms with high absorption time have low reverberation time.  Rooms with high volume have high reverberation time.  Auditoriums typically have reverberation time of 1.5 seconds.  Classrooms have typical reverberation time that varies between 0.5 and 1.5 seconds.

65. .  A Finitzo-Heiber study was done to measure average speech understanding of normal hearing and hearing impaired students in classrooms of different reverberation times and signal to noise ratios.  Overall, classrooms with lower reverberation times and higher signal to noise ratios provided better listening conditions for both groups of children.

66. Effects of Reverberation on Understanding Speech  Decrease overall understanding of speech  Vowels interrupt the understanding of lower loudness consonants. Vowels tend to be 10-15dB louder than consonants.  Silent intervals between syllables, sounds, and words are filled with reflected energy resulting in a smearing effect of the sound.

67. Ways to Reduce Reverberation Time  In order to reduce reverberation time, you need to increase absorption.  Absorption can be increased by replacing of covering hard surfaces with softer ones to minimize the amount of reflection

68. In a classroom with no absorption or attempt to reduce reverberation, the reverberation time is about 1.65 seconds.  Draperies addedRT=.95 sec  Carpet added RT=.52 sec  Foam padding under carpet RT =.36 sec  Acoustic Tile on Ceiling RT =.22 sec  Padding can also be added to walls:  bulletin boards  tapestries  felt boards  carpet squares on walls

69. Distance  The greater the distance between the teacher and the child, the more difficult it is for the child to receive the speech signal due to decreased loudness.

70. V. Daily Inspections of FM Systems in the Classrooms

71.  Daily visual inspections of the FM equipment is important to ensure that the students are getting a clear signal and that the equipment is functioning properly.  Once a FM is chosen and fit for a child, the teacher should have information about the FM system handy on file.  The file should include items such as: correct settings for FM, troubleshooting equipment, who to contact in case of problems, and how to charge the system.

72.  Each morning, the teacher should inspect each child’s FM system following an auditory trainer check guide:  Physical inspections- check for wax and debris in ear molds, feedback in the ear, visible cracks/cuts in external cords, and movement of on/off switch.  Check receiver in hearing aid only mode- check for no FM light on, low battery light on, static in right/left output jacks, and movement of volume control.  Teacher transmitter- make sure unit is on mic/audio and that the microphone has no static when wiggled.  Check receiver in FM only mode- make sure frequency same as teacher transmitter, check for no Fm light, check for clear and static free signal.

73.  An audiology notebook should remain close-by containing equipment information and a troubleshooting guide.  If a problem is encountered, the teacher can reference the audiology notebook, the child’s individual file, and/or an audiologist.

74. VI. Motivating Students

75.  Establish a program where older students help the younger ones with their daily inspections  Develop a Daily Inspection Log where the children get stickers to “check off” the steps taken to reinforce the procedures that must be taken to receive optimal benefit from the FM system and to promote future independence from the teacher

76.  Give other rewards such as certificates or monthly report cards describing the student’s success with using the FM system to encourage the students to consistently wear their aids/FM systems at home and school, to perform daily inspections on their own and inform the teacher of any malfunctions

77. VII. Resources for Teachers

78.  Web Sites:  www.utdallas.edu/~thib  www.audioenhancement.com  www.members.tripod.com/listenup/assist.htm#13  www.members.tripod.com/listenup/assist.htm#14  www.agbell.org/programs/programs.html#information

79.  Books:  Acoustics and Sound Systems in Schools, Frederick S. Berg  Facilitating Classroom Listening: A Handbook for Teachers of Normal & Hard of Hearing Students, Frederick S. Berg  FM Auditory Training Systems: Characteristics, Selection, & Use, Mark Ross