I. Classroom Location and Room Number

Bulacan State University – Natividad Hall, 4th floor, Room 408

II. Classroom Dimensioning

Pictures while measuring the room

III.Room Layout

3D VIEW

DIMENSIONS

DETAILED INTERIOR DIMENSIONING

CEILING

Area of the CeilingA = (25.5)(24.79)-[(0.85)(0.64)+ (2.28)(0.85)+(0.88)(0.85)]

A = 628.91 ft 2

FLOOR

Area of the Floor

A = (25.5)(24.79)-[(0.85)(0.64)+ (2.28)(0.85)+(0.88)(0.85)]

A = 628.91 ft 2

FRONT WALL

BACK WALL

Area of the Back Wall/Front WallA = (24.79)(8.21)A = 203.53 ft 2

Area of the Chalkboard

A = (16)(4.04) = 64.64 ft 2

Area of the Back Wall/Front WallA = (25.5)(8.21)A = 209.36 ft 2

Area of the DoorA = (3.5)(6.85) = 23.98 ft 2

Summary

Parts No. Area (ft2) Total Area (ft2)

Ceiling 1 628.91 628.91Floor 1 628.91 628.91

LEFT WALLWall 1 209.36 209.36Door 2 23.98 47.96Window 2 21.93 43.86Glass (upper part of door) 2 3.89 7.78

RIGHT WALLWall 1 209.36 209.36Window 4 19.80 79.20

BACK WALLWall 1 203.53 203.53

FRONT WALLWall 1 203.53 203.53Chalkboard 1 64.64 64.64

IV. List of Absorption Coefficients

Floor Materials 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz

Carpet 0.01 0.02 0.06 0.15 0.25 0.45Concrete (unpainted, rough finish) 0.01 0.02 0.04 0.06 0.08 0.1Concrete (sealed or painted) 0.01 0.01 0.02 0.02 0.02 0.02Marble or lazed tile 0.01 0.01 0.01 0.01 0.02 0.02Vinyl tile or linoleum on concrete 0.02 0.03 0.03 0.03 0.03 0.02Wood parquet on concrete 0.04 0.04 0.07 0.06 0.06 0.07Wood flooring on joists 0.15 0.11 0.1 0.07 0.06 0.07

Seating Materials 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz

Benches (wooden, empty) 0.1 0.09 0.08 0.08 0.08 0.08Benches (wooden, 2/3 occupied) 0.37 0.04 0.47 0.53 0.56 0.53Benches (wooden, fully occupied) 0.5 0.56 0.66 0.76 0.8 0.76

Benches (cushioned seats and backs, empty) 0.32 0.4 0.42 0.44 0.43 0.48

Benches (cushioned seats and backs, 2/3 occupied) 0.44 0.56 0.65 0.72 0.72 0.67

Benches(cushioned seats and backs, fully occupied) 0.5 0.64 0.76 0.86 0.86 0.76

Theater seats (wood, empty) 0.03 0.04 0.05 0.07 0.08 0.08Theater seats (wood, 2/3 occupied) 0.34 0.21 0.28 0.53 0.56 0.53Theater seats (wood, fully occupied) 0.5 0.3 0.4 0.76 0.8 0.76

Seats (fabric-upholstered, empty) 0.49 0.66 0.8 0.88 0.82 0.7Seats (fabric-upholstered, fully occupied) 0.6 0.74 0.88 0.96 0.93 0.85

Reflecting wall materials 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHzBrick (natural) 0.03 0.03 0.03 0.04 0.05 0.07Brick (painted) 0.01 0.01 0.02 0.02 0.02 0.03Concrete block (coarse) 0.36 0.44 0.31 0.29 0.39 0.25Concrete block (painted) 0.1 0.05 0.06 0.07 0.09 0.08Concrete (poured, rough finish, unpainted) 0.01 0.02 0.04 0.06 0.08 0.01

Doors (solid wood panels) 0.1 0.07 0.05 0.04 0.04 0.04Glass (1/4 plate, large pane) 0.18 0.06 0.04 0.03 0.02 0.02Glass (small pane) 0.04 0.04 0.03 0.03 0.02 0.02Plaster board (12mm (1/2") paneling on studs) 0.29 0.1 0.06 0.05 0.04 0.04

Plaster (gypsum or lime, on masonry) 0.01 0.02 0.02 0.03 0.04 0.05

Plaster (gypsum or lime, on wood lath) 0.14 0.1 0.06 0.05 0.04 0.04

Plywood (3mm(1/8") paneling over 31.7mm(2-1/4") airspace) 0.15 0.25 0.12 0.08 0.08 0.08

Plywood (3mm(1/8")paneling over 57.1mm(2")airspace) 0.28 0.2 0.1 0.1 0.08 0.08

Plywood (5mm(3/16")paneling over 50mm(2") airspace) 0.38 0.24 0.17 0.1 0.08 0.05

Plywood (5mm(3/16")paneling, 25mm(1") fiber glass in 50 mm(2") airspace)

0.42 0.36 0.19 0.1 0.08 0.05

Plywood 6mm (1/4")paneling, airspace, light bracing) 0.3 0.25 0.15 0.1 0.1 0.1

Plywood (10mm(3/8")paneling, airspace, light bracing) 0.28 0.22 0.17 0.09 0.1 0.11

Plywood (19mm(3/4")paneling, airspace, light bracing) 0.2 0.18 0.15 0.12 0.1 0.1

Ordinary window glass 0.35 0.25 0.12 0.08 0.08 0.08

Absorptive wall materials 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHzDrapery (10 oz/yd2, 340 g/m2, flat against wall) 0.04 0.05 0.11 0.18 0.3 0.35

Drapery (14 oz/yd2, 476 g/m2, flat against wall) 0.05 0.07 0.13 0.22 0.32 0.35

Drapery (18 oz/yd2,612 g/m2, flat against wall) 0.05 0.12 0.35 0.48 0.38 0.36

Drapery (14 oz/yd2,476 g/m2, pleated 50%) 0.07 0.31 0.49 0.75 0.7 0.6

Drapery (18 oz/yd2,612 g/m2,pleated 50%) 0.14 0.35 0.53 0.75 0.7 0.6

Fiberglass board (25mm(1")thick) 0.06 0.2 0.65 0.9 0.95 0.98Fiberglass board (50mm(2")thick) 0.18 0.76 0.99 0.99 0.99 0.99Fiberglass board (53.975mm(2-1/8")thick) 0.77 0.50 0.94 1.17 1.22 1.19

Fiberglass board (75mm(3")thick) 0.53 0.99 0.99 0.99 0.99 0.99Fiberglass board (100mm(4")thick) 0.99 0.99 0.99 0.99 0.99 0.97Open brick pattern 75mm (3") fiberglass 0.4 0.65 0.8.5 0.75 0.65 0.6

Page board over 25mm (1") fiberglass board 0.08 0.32 0.99 0.76 0.34 0.12

Page board over 50mm (2") fiberglass board 0.26 0.97 0.99 0.66 0.34 0.14

Page board over 75mm (3") fiberglass board 0.49 0.99 0.99 0.69 0.37 0.15

Preformatted metal(13% open, over 50mm (2") fiberglass) 0.25 0.64 0.99 0.97 0.88 0.92

Chalkboard 0.15 0.25 0.12 0.08 0.08 0.08

Ceiling Material 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHzPlasterboard(12mm(1/2") in suspended ceiling grid) 0.15 0.11 0.04 0.04 0.07 0.08

Underlay in perforated metal panels (25mm(1") batts) 0.51 0.78 0.57 0.77 0.9 0.79

Metal deck (perforated channels,25mm(1") batts) 0.19 0.69 0.99 0.88 0.52 0.27

Metal deck (perforated channels,75mm(3") batts) 0.73 0.99 0.99 0.89 0.52 0.31

Plaster (gypsum or lime, on masonary) 0.01 0.02 0.02 0.03 0.04 0.05

Plaster (gypsum or lime, rough finish or timber lath) 0.14 0.1 0.06 0.05 0.04 0.04

Sprayed cellulose fiber (16mm(5/8") on solid backing) 0.05 0.16 0.44 0.79 0.9 0.91

Sprayed cellulose fiber (25mm(1") on solid backing) 0.08 0.29 0.75 0.98 0.93 0.76

Sprayed cellulose fiber (25mm(1") on timber lath) 0.47 0.9 1.1 1.03 1.05 1.03

Sprayed cellulose fiber (32mm(1-1/4") on solid backing) 0.1 0.3 0.73 0.92 0.98 0.98

Sprayed cellulose fiber (75mm(3") on solid backing) 0.7 0.95 1 0.85 0.85 0.9

Wood tongue-and-groove roof decking 0.24 0.19 0.14 0.08 0.13 0.1

Miscellaneous surface material 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHzPeople-adults (per 1/10 person) 0.25 0.35 0.42 0.46 0.5 0.5People-high school students (per 1/10 person) 0.22 0.3 0.38 0.42 0.45 0.45

People-elementary students (per 1/10 person) 0.18 0.23 0.28 0.32 0.35 0.35

Ventilating grilles 0.3 0.4 0.5 0.5 0.5 0.4Water or ice surface 0.008 0.008 0.013 0.015 0.02 0.025

V.Computation of Noise Reduction Coefficient (NRC)

The NRC is the arithmetic average of the sound absorption coefficients “α” at 250 Hz,

500 Hz, 1000 Hz and 2000 Hz frequencies for acoustical materials.

NRC=α 250+α500+α1000+α2000

4

These are the lists of materials and its NRC that can be seen from the classroom assigned.

MATERIALS 250 Hz 500 Hz 1 kHz 2 kHz NRCFLOOR MATERIALS

Marble or lazed tile 0.01 0.01 0.01 0.02 0.0125WALL MATERIALS

Concrete block(painted) 0.05 0.06 0.07 0.09 0.0675Ordinary window glass 0.25 0.12 0.08 0.08 0.1325Doors (solid wood panels) 0.07 0.05 0.04 0.04 0.05Glass (small pane) 0.04 0.03 0.03 0.02 0.03Chalkboard 0.25 0.12 0.08 0.08 0.1325Fiberglass board (53.975mm (2-1/8") thick) 0.50 0.94 1.17 1.22 0.9575

CEILING MATERIALPlywood 6mm (1/4")paneling, airspace, light bracing) 0.25 0.15 0.1 0.1 0.15

VI. Total Sound Absorption

The sum of all room surface areas times their respective noise reduction coefficients.

aT=∑ Sα

Items NRC Number Total Area (ft2) a (Sabins)

Ceiling 0.15 1 628.91 94.34Floor 0.0125 1 628.91 7.86

LEFT WALLWall (minus the door and window) 0.0675 1 109.4 7.38

Door 0.05 2 47.96 2.40Window 0.1325 2 43.86 5.81Glass (upper part of door) 0.03 2 7.78 0.23

RIGHT WALLWall (minus the window) 0.0675 1 130.16 8.79

Window 0.1325 4 79.20 10.49

BACK WALLWall 0.0675 1 203.53 13.74

FRONT WALLWall (minus the chalkboard) 0.0675 1 138.89 9.38

Chalkboard 0.1325 1 64.64 8.56aT= 168.98

VII. Reverberation Time ( RT(60) or T )

Reverberation is the lingering (perpetuation) of reflected sound within a room after the

sound source has ceased. It is what contributes to the aural “depth” of the sound.

The reverberation period is defined as the time for the sound to decay 60dB after the

sound source has stopped.

T=0.05 VaT

V = [(25.5)(24.79)(8.21)] – {(8.21)[(0.64)(0.85)+(2.28)(0.85)+(0.88)(0.85)]}

V = 5189.91 – 26.52V = 5163.39 ft3

aT = 168.98 sabins

¿0.05 5163.39168.98

T = 1.53 Seconds

VIII. Comparison with the Standard Reverberation Time for a Classroom

Standard Reverberation Time for a Classroom:

0.5 second ≤ RT(60dB) ≤ 0.7 second

The computed reverberation time (T) is greater than 0.5 sec but not less than 0.7 sec.

therefore, it did not satisfy the standard condition given. To reduce the reverberation time,

replacements or adding of new materials is necessary.

Acoustic panels are probably the most common products used to address sound

absorption today. Panels are effective at mitigating sound absorption issues and for the price

(whether DIY or purchased), they contribute nicely to a cost effective strategy.

They are typically made out of a fairly simple set of materials: fiberglass and fabric. They

can be had for relatively inexpensive prices (as cheap as $40-$50 each), but you may want to

consider making these on your own.

Fiberglass board panels 2” thick is being recommended to be added to the back wall for

the treatment of the classroom.

AFTER TREATMENT

Items NRC Number Total Area (ft2) a (Sabins)

Ceiling 0.15 1 628.91 94.34Floor 0.0125 1 628.91 7.86

LEFT WALLWall (minus the door and window)(treated)

0.9575 1 109.4 104.75

Door 0.05 2 47.96 2.40Window 0.1325 2 43.86 5.81Glass (upper part of door) 0.03 2 7.78 0.23

RIGHT WALLWall (minus the window) 0.0675 1 130.16 8.79

Window 0.1325 4 79.20 10.49BACK WALL

Wall (Treated) 0.9575 1 203.53 194.88FRONT WALL

Wall (minus the chalkboard) 0.0675 1 138.89 9.38

Chalkboard 0.1325 1 64.64 8.56

aT= 447.49

T=0.05 VaT

¿0.05 5163.39447.49

T = 0.58 Seconds

After treatment, the standard reverberation time for a classroom has been satisfied.

Therefore, the room is now desirable for learning and lecture purposes.

IX. Noise Reduction (NR) after Treatment

We apply a treatment for the classroom to satisfy the standard reverberation time. Noise

reduction is the reduction of reverberant noise level.

NR=10 loga2

a1

where: a2 = total room absorption after treatment a2 = total room absorption before treatment

NR=10 log 447.49168.98

NR = 4.23 dBNoise is reduced by 4.23dB after treatment.

X. Composite Transmission Losses / Transmission Loss of Common Wall

Room boundaries must be adequate barriers to intruding noise from outdoors and from

adjacent spaces.

CTL= ∑ S

∑ τ STL=10 log 1

τ

Wood (TL = 43 db)

43=10 log 1τ

τ = 5.0119x10-5

Concrete (TL = 46 db)

46=10 log 1τ

τ = 2.5119x10-5

Glass (TL = 31 db)

31=10 log 1τ

τ = 7.9433x10-4

Fiberglass Panel (TL = 25 dB)

25=10 log 1τ

τ = 3.1623x10-3

CTL of Left WallCTL=10 log 109.4+47.96+43.86+7.78

(109.4 x (3.1623 x10−3) )+(109.4 x (2.5119 x10−5 ))+(47.96 x (5.0119 x10−5))

+(43.86 x (7.9433 x10−4))+(7.78 x (7.9433 x10−4))CTL=27.27dB

CTL of Right WallCTL=10 log 130.16+79.20

(130.16 x(2.5119 x10−5))+(79.20 x(7.9433 x 10−4))CTL=35.00dB

CTL of Front WallCTL=10 log 138.89+64.64

¿¿¿

CTL=43.87 dB

CTL of Back WallCTL=10 log 203.53

¿¿CTL=24.97dB

XI. Noise Reduction of Composite Wall

NR=CTL+10 log (a2

s)

NR of Left WallNR=27.27+10 log( 113.19

209.36)

NR=24.60dB

NR of Right WallNR=35.00+10 log( 19.28

209.36)

NR=24.64 dB

NR of Front Wall

NR=43.87+10 log( 17.94203.53

)

NR=33.32dB NR of Back Wall

NR=24.97+10 log(194.88203.53

)

NR=24.78dB

XII. Sound Intensity Level within the room if SIL1 is 75 dB

NR=SIL1−SIL2

SIL of Left Wall24.60=75−SIL2

SIL2=50.40dB

SIL of Right Wall24.64=75−SIL2

SIL2=50.36dB

SIL of Front Wall33.32=75−SIL2

SIL2=41.68dB

SIL of Back Wall24.97=75−SIL2

SIL2=50.03dB

Total SIL2

SIL2 of Left Wall = 1.0964781 x 10−7 W/m²SIL2 of Right Wall = 1.0864256 x10−7 W/m²SIL2 of Front Wall = 1.4723125 x10−8 W/m²

SIL2 of Back Wall = 1.0715193 x10−7 W/m² Total SIL = 3.40165425 x10−7 W/m²

SILT=10 log( II o

)

SILT=55.32dB