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classrooms acknowledges that younger students require _
more favorable listening conditions because they are still -_.:_,y._»_ W‘ - -o
developing their language skills. f“';&‘-es’ "  5" '_
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Cnnaidaring Conditions in   I ‘It’.  l
. . - *  i 3 T . 
Dccuplad Active Glaser-coma ;,._g r . ‘ . . . :: ,_.:,::‘
A great deal of work has gone into the development of  ‘ fl} ‘ ‘ .
ANSI/ASA S12.60, LEED certification requirements, BB93, . I 1 f g ‘ k
and other classroom acoustics standards around the globe. 
They have filled an important void and provided a much
needed basis of acoustic design, but their recommendations E V  ‘
do not tell the whole story; they do not encompass the entire  i T‘
range of acoustic experiences found within occupied active *
classrooms. Figure 4. Many classrooms still use video pmjecm technalagles. This
MW 5‘“d*=s m‘“““"% the "-“ms °f backwnd n°‘S*~‘ §..§}Z.§§f"iZlZ§C,7.§{fI§Z' Zlifliitif.-e;,L"fZ'§Zb.‘i.Z’”l§ztv}';'§'
on speech levels refer to the Lombard effect. The Lombard must compete “gm-"Sp
effect is the involuntary increase in vocal level to compensate  
for higher background noise levels, originally observed by 
French otolaryngologist Etienne Lombard (1911; Brumm I
and Zollinger, 2011). The Lombard effect is often cited as the
reason occupied noise levels in classrooms should be strongly '—a  A 1   ‘
correlated to the unoccupied noise levels. An assumption ' ‘
is made that the background noise level in a classroom is ' "' ' 7 "-3
consistent, regardless of occupancy and primarily the result __ ‘  ,‘
of HVAC systems. Therefore, unoccupied background noise _ ,  — "rt ' ‘ l
levels should significantly relate to the signal-to-noise ratios  ‘ V 1 " ’
experienced by students in occupied conditions due to the ' . '
Lombard effect. That is, higher unoccupied background noise ;/__\5;__/ ,4 I c
conditions should result in proportionally higher talker levels 
in the occupied classroom. However, students in modern ' \
K-12 occupied active classrooms experience background “-.‘
noises that stem from more than the HVAC systems. I ['1' | I
Our observations from visiting classrooms for our study ('ll|,l;’,l,:li)[';,P,v 
confinn that assorted instructional equipment is in common,
though not constant, use. Such equipment should not be Figures. The integration ufmmputers into the curriculum necessi—
djscounmd in guidgfines fecgxnfngndgd in standards, Videg tlltes charging stlltiorlsfur laptops and tllbletspmvided lly the Schuol.
Pm,-mm 3” ml, smples in most classrooms in the United T-hese churgingstutiorls, like tllaaaeshowa here, hagefaas t}lutdis—
Smes‘ some classroom use imemmve whimbomds) like slpate heat thraxfh vent; l'h:s Isl; Isumlre of aperammal muse that
SMART Boards, but many of these interactive whiteboards can mmf/M W” H mm as Spam EVE 5'
still use projector technology (Figure 4). These projectors have
fans to dissipate heat, but the fans radiate noise that contributes The sound levels created by the occupants themselves
to the background noise level in the classroom. We have also should also not be disregarded. Picard and Bradley (2001)
observed numerous laptop/tablet charging carts in classrooms summarized levels of noise in occupied classrooms for
with  fans that ultimately interfere with speech levels students in assorted grades and found the highest levels in
in the room (Figure 5). Instructional equipment can and the classrooms of the youngest children. K-12 classrooms
does contribute to the background noise levels teachers must are complex learning environments in which a number of
compete with to communicate with their students. teaching modalities are used, ranging from single instructor
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