DUMC building science

2. INTRODUCTION
Damansara Utama Methodist Church is one of the prominent
Methodist Church located in the Klang Valley.
It's located at Section 13 within an industrial district.
The building consists of two floors with three mezzanine levels.
DUMC houses an auditorium and three halls.
The auditorium has a capacity of 2301 seats and a volume of
18655m^3 and is used for ochestra, speech, sunday activities &
etc.
BUILDING HISTORICAL BACKGROUND
It was first a shoplot premises in 1988, DUMC moved to Taman
Mayang to accomodarte up to 500 people.
1996 - Chinese church of DUMC was then established resulted in
1000 members.
1997 - DUMC moved to the former Ruby Cinema in SEAPARK.
2001 - DUMC then expanded again with the establishment of Ba-
hasa Malaysia ministry.
2007 - the Dream Centre became the latest premise for DUMC.
Site Location
Exterior of DUMC

3. Shape of Auditorium
The fan-shaped auditorium creates a more intimate space that brings
the audiences closer to the speaker.
Since the distance between the audiences and the speaker is closer, the
sound of the speaker is louder hence improve the listening condition of
the audiences.
The angle of the auditorium is 150 degree which exceeds the maximum
limit of 130 degree for a wide fan arrangement.
A central focus will be formed to create a more intimate relationship be-
tween the speaker and the audiences.
However, the audiences which seated beyond the maximum limit will
have poor listening condition. There should be no seats beyond the max-
imum limit of fan shaped arrangement as the sound level is significantly
lower than the rest of the audience.
Thus to overcome this issue, mechanical audio devices such as three line
arrayed speakers are installed at centre, left and right wings.
The doublestories high auditorium is to accommodate large audiences.
The seating which arranged on level terraces is to provide proper sight-
lines from the audience to the stage.
The staggered ceiling design forms a concave curvature to reflect the
incident sound wave back to the audiences.

4. DISPERSION OF SOUND
INEFFECTIVE SOUND PATH
EFFECTIVE TRANSMISSION AND REINFORCEMENT OF SOUND AIDED BY STAG-
GERED CEILINGS AND RAISED STAGE.
Sound Path

5. Sound shadow area
A sound shadow area is an area which sound wave fail
to propagate.
In this case, a sound shadow area is formed in the audi-
torium under the first floor.
The reflected sound waves fail to reach the people who
stay under the sound shadow area.
Due to the design approach, the sound shadow area is
considered shallow in this auditorium whereby the de-
sign of the second terrace is pushed further outwards
which cast minimal shadow area towards the lower
seating area working together with the staggered ceil-
ing which produces a useful reflection of the sound
wave.
Hence, there are no periphery audio devices required
at the back seating area.

6. Type and location of speaker
The speakers employed to transmit sound for the audi-
ence are all suspended from the ceiling with a height of
approximately 7 meters from ground, to prevent direct re-
flection from the flat ground floor, which might produce
uneven sound concentration.
Line-arrayed speakers are suspended from the ceiling
facing the centre, right and left wings to transmit amplified
sound in tier-arrayed pattern to transmit the sound evenly
to the audiences in every level seat to ensure every audi-
ence receive the same amplitude of the sound.
The subwoofers are suspended in between the line-ar-
rayed speakers to boost the low frequency sound range
by amplifying the base which will resonate in the audito-
rium.
To overcome the shortcoming of suspended subwoofers
which the energy of direct vibration might attenuate in
the air, a parallel hard concrete wall is designed facing
the output source of the subwoofers.
Monitor speakers are positioned in an array manner fac-
ing the stage to ensure the performers receive the sound
simultaneously with the audiences to prevent off-beat of
the performance.
The audiences in the front row are situated in the blind
spot of line-arrayed speakers, thus small speakers are in-
stalled facing them.

7. Seats
The seats are divided into two categories which are fixed
and movable seats to cater different occasion use.
One seat represents the similar sound absorption which a
person posses to ensure the acoustic experience that is
not directly affected by the occupancy of the hall.
The dimension of the cushion seat is 550 with a leg room
of 530 which is comfortable and provide a marginal clear-
ance between a seated person’s knees and the back of
the chair in the next forward row.
Fixed seats arelocated at level terrace on the ground floor
and first floor.
Movable seats are located at the ground floor pit.

8. Delay = (R1 + R2 – D) / 0.34
Ground Floor Fixed Seats Area
R1a + R2a – Da = (11.8 + 17.3 – 18.6) /
0.34
= 30.88msec
First Floor Fixed Seats Area
R1b + R2b – Db = (18.8 + 14.7 – 30) / 0.34
= 10.29msec
Ground Floor Movable Seats Area
R1c + R2c – Dc = (10 + 14.5 – 12) / 0.34
= 36.8msec
Acoustic Defect
Time Delay
According to the calculations, all the time delays are
within 40msec which is acceptable for speech but is
not suitable for music.
A music hall need a relatively long time delay to allow
music to flow and enhance the music quality.
However, the time delay shouldn’t exceed 100msec as
it will cause echo for a music hall.
Echo
Echoes are the distinct repetition of the original sound due
to the reflection of sound waves from an obstructing surface.
There will be an occurrence of echo when R1 + R2 – D >=14m
for lecture hall and when R1 + R2 – D >=34m for music hall.
After the calculation, the result is between 14m and 34m which
are acceptable for a mixed acoustic used hall as it is between
the occurrences of echo for lecture hall and music hall.
R1 + R2 – D = 13.7 + 13.6 - 21.5
= 17.06m

9. However, when we clapped our hands on the longer side of the
first floor seating area, echo can be heard. The time between the
first and second time the sound register in our ear is big enough
for our ear to tell the difference. It is probably due to the reflec-
tion of the sound wave by the Perspex railing. When the sound
wave hit the hard and flat surface, it reflects back. The distance
between the railings is long enough for us to notice the reflected
sound wave.
Flutter Echo
A flutter echo consists of a rapid succession of noticeable small
echoes. The occurrence of flutter echo is due to the sound wave
are trapped between two surfaces and get a series of reflections
in a short time.
Flutter echo is noticeable in this auditorium. A short burst of
sound is produced when we clapped our hand on the first floor
of auditorium. The present of flutter echo probably is due to the
parallel hard sound-reflective surfaces which are the ceramic
floor tile of mezzanine control area and the ceiling above.

10. Noise
The main sources of noise can be classified into two groups
which may be transmitted through air-borne or struc-
ture-borne:
Outdoor Noise Indoor Noise
Impact noise from the hollow timber were being reduce by covering a layer of carpet on it but the noise still can be heard clearly.
For the utility area, thick stage curtain was being installed to reduce the transmission of sound from the backstage.
At both ground floor and mezzanine floor, the noise from sound system were not being treated well.
The noise coming from the
neighbouring room such
as washroom, performers’
changing room, mothers
& infants room and oth-
er room that people will
gather and talking.
Indoor noise produces
by people talking, im-
pact noise from people’s
footsteps and equipment
noise from the machin-
ery such as sound system,
lighting system and air
conditioning system.

11. The reverberation time of large multipurpose auditorium (>7500 cubic meter) is normally 1.0 – 2.0 sec. The
calculation above shows that the reverberation time for this auditorium is 1.61sec, which is suitable to be
a multipurpose hall. Thus, this auditorium could be a mixed acoustical use auditorium which compromises
good speech intelligibility & fullness of music.
R.T. CALCULATION

12. Materials

13. Interior Wall
Plastered walls are only finished with a coat of paint. Dry walls
are installed on the side of the auditorium and balcony. Hard
plastered drywall have very low sound absorption, thus will reflect
the sound waves, forming echoes. To prevent fluttered echoes,
parallelism is avoided on the side walls.
Rear walls of this auditorium are mainly dry walls covered with
Rockwool. This is to absorb the sound from the stage to avoid
echo due to the parallelism ofthe rear walls and the wall be-
hind the stage. Other than that, the low wall of the second
floor acting as the balcony is also installed with Rockwool
membrane. Diffuser is installed on the lower wall, thus Rock-
wool membrane functions as sound absorber to reduce the
noise produced by the HVAC.
On the ground floor, there is a combined use of various mate-
rials on the wall, which is fabric wrapped Rockwool on the up-
per part of the wall and wooden strips claddings on the lower
part of the wall. By installing porous membrane such as Rock-
wool with wrapped fabric on its surface, this could absorb the
mid or high frequencies to reduce the reverberation time,
achieving speech intelligibility. Coarse weaved fabric is used
for the covering of the Rockwool to allow sound waves to dis-
sipate through the porous membrane before being trapped
and dampened. On the other hand, the wooden strips act as
a medium which absorbs the lower frequency that could not
be absorbed by the porous membrane. It also increases aes-
thetic value of the auditorium, giving a sense of warmth to this
worship place.

14. Angled Rockwool acoustic panels finished with soft coarse fabric
are mounted on the wall with an air space gap. The mechanism
principle is similar as cavity absorber, works well with low frequen-
cy range, which is appropriate for the hall as bass reliant music are
mostly played. When the incident sound energy which is already
dampened by the first absorption of the panel enter the air gap, it is
reflected back and trapped, subsequently being attenuated, thus
reducing the reverberation time and avoid fluttered echo. This in-
creases sound absorption, adds aesthetic purposes while providing
indirect lighting as lights are installed behind.
Curtain
Thick and highly porous acoustical curtain is installed at the back-
stage. Behind of the curtain are acoustic panels, followed by con-
crete wall with an air gap in between the curtain and the wall. The
air gap is to absorb the low frequencies while the drapery is used to
absorb the sound, reducing reverberation time and avoid echo.
Movable heavy curtains are also installed at the entrance of the
auditorium and openings as curtain is an absorptive material. It will
not reflect the sound back to the audience, inhibiting speech intel-
ligibility.

15. Ceiling
Majority of the ceiling is made of plaster while some part of the ceiling
is mineral fiber board. Plaster is a kind of material which absorbs low
frequencies and is good in reflecting all other frequencies. Proper
tilted plaster ceiling increasing the length of useful ceiling reflection,-
contributes more useful sound reflection. Audience sitting far away
from the stage is able to hear the sound from the stage.The concave
shape created converges the sound wave. Mineral fiber board is in-
stalled where the square diffusers are. This is because gypsum board
is strong in low frequency absorption.
Floor
Sloped floor is designed in this large mixed used auditorium.
This could improve the sight line of the audience as to avoid
obstructed view for the audience, also known for improving
the fidelity from the seating area. While sitting on the sloping
floor , audience could also receive more direct sound waves
compared to flat flooring.

16. Stage floor finishing is
wooden plank while
most of the flooring is in
carpet.
The carpet is made up
of thin and tight loop
piles of synthetic fibers.
This creates a good
sound absorbent
mateial, dampening
the unwanted noises
created such as foot-
steps, creating a quiet-
er environment.
Exterior Wall
For the exterior wall, another layer of brick masonry wall is built.
Massive thick masonry wall is able to reflect low frequencies,
insulating the sound from the exterior entering the auditorium.
Staggered masonry wall is also able to absorb the mid and
high frequencies, leaving the frequencies in the air gap in be-
tween the overlapping walls.
Part of the exterior wall is cladded with cork. Cork can help to
absorb and dissipate sounds to reduce disruptions. This could
avoid unwanted noise entering the auditorium.

17. Doors, Openings & Windows
Cons:
Thin glass is a poor soundproof insulator due
to its hard and light dense properties. When
incident sound waves hit its surface, it vi-
brates and resonates along, producing un-
wanted noise.
Suggestion:
Install a curtain layer to increase absorption.
Cons:
- Wood is a bad sound absorbance mate-
rial some door are installed without curtain
- door still have gap which allows sound to
escape through.
Pros:
- Using curtains as sound deflector & absorb-
er to avoid the sound inside being transfer to
outside.
Suggestion:
installing door seal to further soundproofing
the hall.

18. Air Diffuser
There are several types of air diffusers in the auditorium
which are louvered bladed diffuser, jet diffuser and linear
slot diffuser. Both ground floor and first floor consist of sup-
ply and return air diffusers.
Issue:
Conical cone jet diffusers are used at the ground floor for
supply air in the area where the ceiling is high. Howev-
er, they produce larger noise because large air velocities
are needed to reach the occupied space.
Suggestion:
The use of rock wool insulation lining along the internal
duct can effectively eliminate noise along ducts as the
insulation has good sound absorption properties to ab-
sorb noise attenuated within the ducts.

19. Lighting
Several types of lighting fixtures were installed all over the
auditorium.
The buzzing of lighting fixtures when switched on also
became one of the noise sources that affect the experi-
ence of the users.

20. THE END