2. identifying the need
The teacher has just asked a question If you’ve ever taken a foreign language
about last night’s homework. Wanting class or tried to converse at a loud
to encourage participation from those party, you know how exhausting it can
who rarely raise a hand, she decides be. Trying to understand someone
to call on Sally. under adverse conditions such as
distance, noise, reverberation and poor
“Sally, where is the
acoustics — all of which are a part
Rio Grande River?”
of everyday life in our schools—make
Sally looks at the teacher, it extremely difficult for kids to focus
perplexed. Did she just on the teacher
ask where the real train
Good speech intelligibility is crucial for
was driven?
the development of auditory and lan-
This scenario is typical in the average guage skills in all children. Many remain
classroom. According to the Acoustical silent about the difficulty they are having
Society of America, “Students with discerning speech in the classroom. Like
normal hearing in the average Sally, they may become confused, or
American classroom miss 25% worse— give up. Unfortunately, until the
of what the teacher is saying.” teacher or a family member begins to
1
3. take notice of the real problem, students they are seated in the middle to back
like Sally may be perceived as apathetic of the classroom.
or incapable of learning the material.
Fundamental to the problem is child-
hood itself. Children’s auditory process-
the communication es are not fully developed until their
connection mid-teens, and they don’t have the life
experience to be able to “fill in the
Studies have proven that in noisy
gaps” when they do miss information.
environments the more than 2 million
school children learning English as a As we’ll see in the next section,
second language (ESOL) have more noise, distance, and reverberation
difficulty with speech perception than all exacerbate these fundamental
native English speakers, especially if problems.
2
4. distance
Distance is a significant obstacle to speech signal, and can achieve
speech understanding. Audibility 95% word recognition.
decreases as the distance from the
Students in the middle row, however,
speaker increases (about a 6dB drop
hear the teacher at 59dB — already
for every doubling of distance). At a
below typical classroom noise levels —
certain distance, the background noise
receive 66% of the speech signal, and
can effectively mask the speaker’s voice.
achieve 71% word recognition.
A typical teacher’s voice measures 60 The situation is worse for back-row
to 65dB at a distance of 1m/3ft. This students, who hear the teacher at 53dB,
means that front-row students hear the receive 55% of the speech signal, and
teacher at 65dB, receive 83% of achieve just 60% word recognition.
2
3
5. noise
Noise can cause a general breakdown Playground squeals, desk and chair
of communication and missed infor- movement, chatting students, fans, and
mation. For ESOL students this heaters all result in a typical noise level
becomes especially true as they try — of 60dB — almost as loud as busy street
and often give up — discriminating traffic. And since a teacher’s comfortable
between competing background speaking volume is only 60dB at 3ft/1m,
noise and the teacher’s voice. she has a difficult time simply being
heard by her pupils.
4
6. reverberation
Noise and reverberation (also Vowels — the low-frequency
referred to as echo) are synergis- sounds representing 60% of
tic. Hard walls, high ceilings, glass speech energy, but only 5%
windows, and uncarpeted floors of speech meaning — often mask
reflect many sounds, often with the weaker consonant sounds,
a negative impact on speech which contain far more speech
understanding. meaning (compare cat, bat,
sat, pat). As a person
Reverberation time
speaks louder, the vowels
should be less than
are emphasized, further
0.4 seconds to avoid
obscuring meaning.
decreasing intelligibil-
ity, yet the typical
classroom averages
0.8 seconds rever-
beration time.
Effects of Reverberation & Signal-to-Noise Ratio on Word Discrimination
Word discrimination
scores of Signal-to-Noise Ratio
students with Quiet Noisy
normal hearing
Reverb 20 +12 +6 0
Classroom with
carpet, curtains, 0.0 95% 89% 80% 60%
some acoustic
treatment 0.4 93% 83% 71% 48%
Typical classroom
(no carpet, etc.) 1.2 77% 69% 54%2 30%
Figures in boldface indicate acceptable WDS scores. Without a sound field
system, these scores are achievable only in quiet or acoustically treated rooms.
Also note that this chart does not consider distance; even in quiet, acoustical-
ly treated rooms, children at the back will have compromised understanding.
5
7. signal-to-noise
signal-to-noise noise level of an 18-wheel truck —
simplified to provide the +6dB S/N required
at the back of the room.
As we’ve seen, intelligibility is not the
same as mere audibility (i.e., simply We could reduce the noise and rever-
having the teacher speak louder is beration in the classroom by adding
not the answer). In fact, intelligibility acoustic treatments and
is directly related to signal-to-noise demanding that
ratio (S/N) — the difference between
ambient room noise and the speak-
er’s voice (the signal). The greater
the S/N, the greater the intelligibility.
Let’s look at an example. Average
classroom noise is 60dB. The average
teacher speaks at 60 - 65dB measured
at 3ft/1m. Thus, you would have +5dB
S/N at a distance of 3ft/1m from the
speaker — and we know from the pre-
vious sections that this will only decline
the farther away from the teacher a
child sits. Indeed, typical classroom sig- the children be quiet, but this is an
nal-to-noise values are -7 to +5 dB expensive or futile effort. Nor does
overall (see chart for the effect signal- it address issues of distance.
to-noise has on speech recognition).
A more effective method is to move
Yet normal-hearing children require at-risk students closer to the teacher.
at least +6dB S/N — how can we This is only practical for a few stu-
achieve this by altering the variables dents, however, and doesn’t allow
of distance, noise, and reverberation? for much movement by either the
teacher or the student.
We could increase the signal by
having the teacher raise her voice — Overall, these situations are not very
the common solution. Yet this only encouraging. Is it worth the effort,
increases teacher vocal fatigue and then, to improve signal-to-noise ratio?
sick leave, and would require the Numerous studies show the answer
teacher to speak at 94dB — the to be an emphatic YES.
6
8. the importance of acoustics
There’s no getting around the impor- Finally, there’s overwhelming empiri-
tance of good speech intelligibility in cal evidence showing that improved
schools. Classrooms are clearly auditory- S/N results in better student atten-
verbal environments — children spend tion, comprehension, test scores, and
as much as 45% of the school day in on-task behavior.
a listening situation. Language develop-
Log on to www.phonicear.com
ment occurs early in life, and what’s
to order reprints of these studies
more, literacy is directly related to audi-
or go to the links where provided
tory development. Kids who have good
and download.
listening experiences tend to become
better readers. With the help of wireless technology,
it’s actually possible to improve signal-
In addition, much of the material and
to-noise ratio without seating restric-
vocabulary is new to students — they are,
tions or costly modifications to
after all, just learning.
classroom construction.
From an academic perspective,
difficulty hearing and understanding
leads to disruptive behavior.
2
7
9. the sound field solution
It’s called sound field, and it
consistently provides:
• Compensation for the variables that • 8 to 10 dB S/N ratio and up to
adversely affect signal-to-noise ratio 30% improved speech recognition
• The ability for any child anywhere • Better test scores —
in the room to hear the teacher as if often dramatically better
he or she were only a few feet away
• Improved attention and behavior
• A focus on the teacher —
• Reinforcement of language develop-
not background noise or echo
ment and literacy in all students
8
10. how does it work?
In the same way that sitting close Did you catch that? Sound field uses
to the teacher results in a the advantages of close proximity to
positive signal-to-noise the sound source twice — first by
ratio and strong speech placing the microphone close to
discrimination, a wireless the teacher’s mouth where it picks up
sound field system a strong signal nearly free from back-
delivers a clear, intelli- ground noise, and second by placing
gible speech speakers closer to the students. In
signal by effect, the teacher is never more than
reduc- a few feet from students, and a gentle
ing key amplification brings the signal-to-noise
distances. ratio above the 6dB requirement.
First, the teacher wears a small wire- Amplification allows teachers to speak
less transmitter with a microphone in a normal voice and since it’s wireless,
placed within 6in/11cm of his or her they can move freely around the room
mouth (or connected from a receiver or turn to face the chalkboard while
directly to a VCR, CD player, etc. for a effortlessly maintaining the level of his
surround sound kids love). or her voice.
His or Her voice signal is transmit-
ted across the room through radio
wave or infrared light, bypassing
the effects of distance, noise,
and reverberation.
The teacher’s voice signal is then
brought close to students’ ears
through speakers placed around
the room.
9
11. does it really work?
Since the 1970s over 50 studies What do audiologists and teach-
have been conducted to find out just ers have to say about sound field?
how much difference sound field
“Students in the classrooms with an FM
systems make.
sound field system achieved greater liter-
In Florida from 1993-95, an extensive acy gains than control students. Twice as
study on “Improving Classroom many students achieved up to seven
Acoustics” was conducted among 2,054 reading levels of literacy growth com-
students in 94 kindergarten, first and pared to the control students.”
second grade classrooms. Sound field Beata Darai, Aud, FAAA
was installed in 64 classrooms, while 30 “Using Sound Field FM Systems
to Improve Literacy Scores”
classrooms acted as the control group.
Advance for Speech-Language
Some of the findings include: Pathologists and Audiologists
• 96% of teacher agreed that
attentiveness, listening, and “Numerous investigations have shown
comprehension improved that when sound field amplification
systems are used, psychoeducational
• 100% of school administrators agreed
and psycho-social improvements
that teachers enjoyed the systems
occur, academic gains were obtained
• 92% of administrators thought that at a faster rate, to a higher level, and
sound field enhanced class instruction with reduced cost.”
and management Carl Crandell and Joseph Smaldino
“Room Acoustics for Listeners
Other studies have found: with Normal Hearing and Hearing
Impairment” Audiology: Treatment
• Vocabulary test scores improved
by 12% with sound field.
“Before sound field only 44-48% of
• Spelling test scores of 3rd, 4th, and
1st grade pupils tested at the ‘basic’
5th graders have been shown to
level and above. After seven months of
improve by 14.5%, 9%, and 22.4%
sound field 74% of children tested at
respectively when using amplification.
the ‘basic’ and above level. Students
• Comparative results from project also showed significant improvement
MARRS (Mainstream Amplification in vocabulary, word-usage skills, and
Resource Room Study) indicated were much more likely to answer
that students in an amplified class- questions appropriately.”
room showed significant improve- Linda Crozier, MA, CCC-SLP
ments in Scholastic Reading W. Russell Todd Elementary School,
Achievement scores. Roosevelt, Utah
For many more references visit www.phonicear.com 10
12. which system?
There are several sound field system sound quality, speech clarity, and
options, each with its own special simplicity, this system lives up to its
advantages and applications. name — EASYLISTENER 2. Easy to use —
easy to hear the difference! A team-
teaching option with a handheld mic
is also available.
Our popular, portable, RADIUM
system let’s you choose from 16
channels on both the receiver
and transmitter — no preselection
of channels required. It sets up
in minutes and is very afford-
able, making it a great
choice for first time sound
field users. With two speak-
ers housed in one unit,
RADIUM can easily improve Unlike RADIUM and EASYLISTENER 2,
the listening environment which transmit sound using radio
in almost any classroom. And frequencies, VOCALIGHT uses infrared
because it’s battery powered and com- light. The advantage is the ability to
pletely portable, you can even use it use an unlimited number of systems
for outdoor events, physical education, in the same building. Since infrared
assemblies and more! RADIUM also light can’t penetrate walls, every class-
features two built-in channels for room can use a VOCALIGHT. Our
easy team teaching and a student infrared technology is also immune
pass around mic. to interference from ballast lighting or
indirect sunlight. VOCALIGHT offers two
built-in channels for team teaching
and a pass around mic.
The new EASYLISTENER 2 transmits
the teacher’s voice through four high-
performance compact speakers
positioned around the class-
room. While this requires more
installation than the RADIUM, the
advantage is OptiVoice, our exclu-
sive speech clarity control. Designed
from transmitter to speakers for
11 Try any system for 45 days!
13. which features?
features RADIUM EASYLISTENER 2 VOCALIGHT
technology FM FM infrared
frequencies 216MHz 216MHz 2.3/2.8 MHz
built-in channels 2 1 2
approximate installation time 5 minutes 60 minutes 90 minutes
relative cost $ • $$ $ • $$ $ • $$
number of systems per install 8 -16 19+ no limit
aux input (CD, TV, computer etc.) 1 (4 with aux box) 1 (4 with aux box) 1 (4 with aux box)
aux output
1 1 1
(interfacing/rebroadcasting)
3-band equalizer no yes no
OptiVoice™ speech clarity control no yes no
4 wall or ceiling, 4 wall or ceiling,
speakers 2 in 1 column or 1 ceiling or 1 ceiling
yes – with yes – with yes – with
team-teaching option additional receiver/
handheld mic handheld mic
handheld mic
66x14x10 cm 21.9x5.4x16.2 cm 22x21x5 cm
receiver size 25.9x5.7x3.9 in 8.6x2.1x6.4 in 8.5x8.3x1.8 in
These charts are provided as an
which speakers? overall guide for system selection.
Recommendations may vary
according to room configurations.
features RADIUM 4 compact spkrs 4 distributed* ceiling cluster*
portability yes no no no
quick installation yes no no no
cost $ • $$ $ • $$ $ • $$ $ • $$
sound dispersion very good best best good
*ceilings must be at least three meters or higher than ten feet for distributed ceiling speakers;
higher than 12 feet for cluster speakers. Four speakers are usually best for rooms approximately 12
30x30 ft or 9.1x9.1 m or more.
14. which mic?
features boom earhook IR lapel FM lapel collar
comfort good good excellent excellent good
feedback excellent very good fair fair fair
resistance
sound quality excellent good fair fair fair
boom mic earhook mic
head-worn
mics
infrared lapel mic FM lapel mic
(wear as shown or clip on)
lapel mics
infrared collar mic collar mic available in
FM or infrared. FM ver-
sion has mute switch
collar mics
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15. funding
Even after they recognize the benefits If you don’t have access to a computer,
of sound field, some schools and call us at 800-227-0735 then press 5,
school districts don’t feel they have and ask to receive our Funding and
money available — that’s where grants, Grant Writing Packet, which lists many
funds, benevolent groups, and creative ways to obtain funding, the differences
fund-raising can help. between funding sources, and places
you can call for more information.
There are numerous grants available
from government education programs,
corporations, and nonprofit groups
totaling billions of dollars. In addition,
some schools have been able to
access funds through their technology
budget, while others have benefited
from fund raisers held by the local
Parent/Teacher Association, Rotary
Club, or other benevolent groups.
The easiest way to begin is to
visit www.phonicear.com
and go to our funding guide where Phonic Ear also offers a free 45-
we have links to many grant and day evaluation so that you can expe-
fund-raising sources. rience firsthand how sound field can
benefit both students and teachers.
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