Page 18 - Fall_DTF

Building a Suund Future fur Scudenx '1
H em

Figure 1. The spatial decay ofthe saund pmsare level in the reve1— I as

lrerant field afa classraarn. ihe sound pressure level at 3 feet (1 me— § ' g -W

te1)f1om a talker is 55 dB(A). Blue urea, region within +15 de sig— Lg’ 2 W
rlal—to—rll2ise ratio (SNR); red urea, levels lower than the lrackgraand .1 ll

naise level (BNL). where the lrlue and red areas intersect, listeners g - “‘ V__

at that distance from the talker will expefierlce lower than +15 dB 3 ,,,,..

SNR. Top: when the BNL is 45 i1B(A), only students sitting within 9 .§ '

feet of the teacher will hear the lesson with a suyjficient SNR. Middle: '5

A 40 dB(A) background noise level can meet the desired +15 dB SNR M

in classraams where the lurgmt dirnensian is less than 30 feet. Bot-

mm: Designing classroom lrackground naise levels ta he at mast 35

i1B(A) ensures that students sitting anywhere within a classraarn will u -- at
experience a mi: ofut least +15 dB, even with talkers that pradace We” '2" W MW

slightly lower voice levels.

teachers and their students, and doing so can be particularly '" f ‘W ,_,

important for children as they are still developing their i >~- 5 arm-

language skills (Klatte et al,, 2010). E W 3 ‘
Classroom speech levels are an important factor in E .. Ir x

determining the maximum recommended background ‘_ ""

noise levels, The American Speech-Language-Hearing E I
Association (1995) recommends a signa.l-to-noise ratio of at ‘'''W”4 .

least +15 dB to ensure high speech intelligibility for children ~ -

with language and hearing impairments. Bradley and Sato

(2008) found that an even higher signal-to-noise ratio of +20 1 :_ " W 3"

dB was preferable for the youngest students in their study D441!-D-Milli-U-W-tmstoovv

(grade 1) to attain near-ideal speech communication. Astudy “l

by Pearsons et al, (1977) showed that the A-weighted sound "“

level of teacher’s speech is typically 67 dB(A) at a distance .,j. ‘ 5*“

of 1 meter in a quiet classroom. Because sound levels are _ “T V Y"

expected to decrease approximately 3 dB per doubling E M‘ “A

of distance in a classroom, the levels of the talker could E "’ 5

diminish to be as low as 55 dB(A) in the rear of a typical E w * '”‘

classroom in the United States (Figure 1). To conservatively u ,_, l _

ensure a minimum + 15 dB signal-to-noise ratio everywhere 3 ‘ .

in the classroom, the ANSI standard set the recommended M,’

background noise level to not exceed 35 dB(A), Meeting "“"""

this recommended maximum noise level achieves a suitable a
signal-to-noise ratio for high speech intelligibility, thereby ,. .. '1'! N.
positively influencing student learning. ”"“"°' "°"“"""“""°"“'°°"‘

An assumpfiml has been ‘hm impmviljg speech For example, in situ studies focusing on aircraft noise in the
intelligibility results in improved student achievement. _
However, only a few studies before the introduction of -classroom have shown that greater exposure to such noise
ANSPS smndard in 2002 showed 3 direct linkbetween noise is related to lower reading scores for elementary students
levels and actual student learning outcomes (Bronzaft, (smnsfeld 8‘ al" 2005; Klaus at Eli’ 2017)’

1981). Investigations completed after the introduction of the Moreover, Shield and Dockrell (2008) surveyed classrooms
standard have provided more evidence that poor classroom with noise sources more commonly found at elementary
acoustic conditions correlate to worse student performance. schools (e.g., traflic, ventilation systems) in both occupied
15 1 Acuulclcl Tbdny 1 5.11 2013