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Evaluation of acoustical conditions for speech communication in working elementary school classrooms
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10.1121/1.2839283
/content/asa/journal/jasa/123/4/10.1121/1.2839283
http://aip.metastore.ingenta.com/content/asa/journal/jasa/123/4/10.1121/1.2839283

Figures

Image of FIG. 1.
FIG. 1.

The relationship between the sound absorption of the occupied classrooms and that of the unoccupied rooms in the and double-octave band.

Image of FIG. 2.
FIG. 2.

The relationship between predicted values for free field conditions with and measured values in the classrooms. The least-squares best fit regression line was given by .

Image of FIG. 3.
FIG. 3.

(open circles) and (closed triangles) as a function of source–receiver distance. Solid lines represent the least-squares regression lines ( for and for ). The dashed lines are the predictions of Barron’s revised theory.

Image of FIG. 4.
FIG. 4.

Comparison of measured and predicted sound strength components, , , , and using a modified version of Barron’s revised theory. The correlation coefficients and rms errors of the estimates are included in each panel. The total number of points for each figure is 120.

Image of FIG. 5.
FIG. 5.

Predictions of various components of sound strength, , , , and using the modified version of Barron’s revised theory presented as a function of source–receiver distance . , were used as the mean values for the measured classrooms.

Image of FIG. 6.
FIG. 6.

Relationship between reverberation time and for , 4, and .

Image of FIG. 7.
FIG. 7.

Relationship between reverberation time and ERB for , and .

Image of FIG. 8.
FIG. 8.

The relationship between reverberation time and values.

Image of FIG. 9.
FIG. 9.

The relationship between reverberation time and values.

Image of FIG. 10.
FIG. 10.

Example frequency distribution of rms sound pressure levels of the recorded segments and the fitting of two normal distributions to the data. The left part of the distribution includes the predominantly noise segments (mean , s.d. 2.8) and the right part the predominantly speech segments (mean , s.d. 6.7). Summation of both normal distributions is shown by the solid line and is seen to approximate the measured data.

Image of FIG. 11.
FIG. 11.

Frequency distributions of the speech and noise levels of 108 points in 27 active classrooms.

Image of FIG. 12.
FIG. 12.

Frequency distribution of mean speech-to-noise ratios for the 108 points in the 27 active classrooms.

Image of FIG. 13.
FIG. 13.

Relationship between room average teachers’ voice levels and noise levels during an active class. Each point is from the average of the measurements at the four microphone positions in each classroom.

Image of FIG. 14.
FIG. 14.

The relationship between noise levels in active classrooms and those in quiet but occupied conditions.

Image of FIG. 15.
FIG. 15.

Frequency distribution of values from the 108 measurement points in 27 active classrooms.

Image of FIG. 16.
FIG. 16.

Open circles are measured points with less than . Closed-triangles are for conditions with .

Image of FIG. 17.
FIG. 17.

Relationship between reverberation time and direct+early speech level, late speech level, background noise level, detrimental sound energy level, and . Detrimental sound energy is the summation of the late speech level and the background noise level.

Image of FIG. 18.
FIG. 18.

Initial part of measured impulse response and the time window used to obtain the energy of direct sound.

Tables

Generic image for table
TABLE I.

Mean dimensions of the 30 classrooms and the number of children present.

Generic image for table
TABLE II.

Reverberation times , early decay time (EDT), and early-to-late energy ratios for both occupied and unoccupied classrooms.

Generic image for table
TABLE III.

Mean measured sound absorption for occupied and unoccupied classrooms and the mean absorption per student from these measured values in the 30 classrooms.

Generic image for table
TABLE IV.

Mean background noise levels in occupied classrooms without student activity and in unoccupied classrooms in each octave band along with the overall -weighted noise levels for each condition.

Generic image for table
TABLE V.

Average speech levels, noise levels, and speech-to-noise ratios for each grade measured in an active class.

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/content/asa/journal/jasa/123/4/10.1121/1.2839283
2008-04-01
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Evaluation of acoustical conditions for speech communication in working elementary school classrooms
http://aip.metastore.ingenta.com/content/asa/journal/jasa/123/4/10.1121/1.2839283
10.1121/1.2839283
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