The document is a comprehensive acoustic study of a speech hall at Al-Nahrain University, detailing its architectural elements and acoustic properties. Key findings include calculations of reverberation time, identification of acoustical defects such as echo and flutter echo, and assessments of sound concentration and shadow effects. The hall's design includes features optimized for speech, such as sound isolation and a capacity of 258 seats.

1. SPEECH HALL
ACOUSTIC STUDY
‫النهرين‬ ‫جامعة‬
–
‫الهندسة‬ ‫قسم‬
–
‫عمارة‬ ‫هندسة‬
‫الرابعة‬ ‫المرحلة‬
2020
-
2021
‫جبار‬ ‫ازهر‬ ‫حسين‬ ‫الطالب‬

2. Index Subject page
Information + Floor plan 3
Section 4
Reverberation time 5
Optimum Reverberation time 6
Sound Reflector Diagram 7
Ray-Diagram Measurements 8
Acoustical Defects 9
Echo 10
Flutter Echo 11
Sound Concentration 12
Sound Shadow 13
Whispering Gallery 14
Resonance 15
Resonance Calculations 16
Sources 17

3. Floor plan
INFORMATION:
• The hall is meant for
speech purposes.
• Double wall for sound
isolation.
• 10 columns + 5 beams
• Hall area = 320m²
• Single seats = 168
• Four seats tables = 6
• Six seats tables = 11
• Total seats = 258

4. Section

5. Building element Area (m²) Material Abso. Ʃ S = A
Ceiling 20x16= 320 Concrete
unpainted
.31 99.2
Back wall 5x16= 80 Gypsum
wall
.05 4
Front wall 5x16= 80 Plywood .17 13.6
Side walls 5x20=100
Two walls = 200
Plywood .17 34
Floor 16x20= 320 Carpet .57 182.4
333.4 Sabin
Reverberation time
RT = .161 X (1600/333.4) = 0.77264 sec
Volume = 20 x 16 x 5
= 1600 m³

6. TR = 4 [ .012 ( 1600 )1/3 + .107 ]
= 4 [ .012 ( 11.696 ) + .107 ]
= 4 [ .1403 + .107 ]
= 4 [ .2473 ] = 0.9894 sec
Optimum Reverberation time

7. Sound Reflector Diagram

8. Ray-Diagram Measurements
Path difference for Big triangle = (4.36 + 10.84)
– 14.45 = 0.75m = 2.46 ft
Path difference for Small triangle = (1.66 + 3.84)
– 3.11 = 2.39m = 7.84 ft
Excellent for speech and music because path
difference is less than 23 ft.

9. ACOUSTICAL DEFECTS
Echo
Flutter Echo
Sound Concentration
Sound Shadow
Whispering Gallery

10. S
L
D = 11.2m
R1 = 19m
R2 = 12.8m
if (R1+R2) – D ≥ 14 For speech
hall than it will be echo in it.
(19+12.8) – 11.2 = 20.6
20.6 > 14
So there is echo in the hall.
Echo

11. Flutter Echo happens when:
between parallel sound reflective surfaces
Width of space / Length of space << 0.6 x Length of space
Height of space / Length of space << 0.6 x Length of space
16/20 << 0.6x20 → .8 << 12
5/20 << 0.6x20 → .25 << 12
There is Flutter Echo in the hall.
Flutter Echo

12. Sound Concentration
Sound Concentration: Also referred to as Sound Foci. Sound
reflections from concave surfaces concentrating on a single
area
Our hall is flat surfaces so sound concentration
does not appear in it.

13. Sound Shadow
Occurs when an area does not receive an adequate amount of
direct sound.
No sound shadow in our hall.

14. Whispering Gallery
also referred to as Creep. High frequency sounds creeping
along large concave surfaces such as a hemispherical dome.
No Whispering Gallery in our hall.

15. Resonance
Room Resonance: also called Coloration.
Occurs when certain sounds within a narrow band of
frequencies tend to sound louder than other frequencies
L = 20m
W = 16m
H = 5m

16. Resonance Calculations
1 0 0
20 16 5
340
L - = 8.5 Hz
0 1 0
20 16 5
340
W - = 10.625 Hz
0 0 1
20 16 5
340
H - = 34 Hz
1 1 1
20 16 5
340
L,W,H - = 36.622 Hz

17. Sources
Acoustic lecture 4 Sound Reflectors
- Dr. Susan Abed Hassan
Acoustic lecture 5 Reverberation Time
- Dr. Susan Abed Hassan
Acoustic lecture 6 Reverberation Time
- Dr. Susan Abed Hassan
Acoustic lecture 7 Acoustical Defects
- Dr. Susan Abed Hassan