Determination Of Sound Transmission Class (STC) For Lecture Rooms In UTeM.

DETERMINATION OF SOUND TRANSMISSION CLASS (STC)
FOR UTEM LECTURE ROOM

ZAINORDIN ZHAFRAN BIN ZULKEFLI

UNIVERSITI TEKNIKAL MALAYSIA MELAKA
FACULTY OF MECHANICAL ENGINEERING

‘I / we admit that have read this work and in my / we opinion this work
satisfied the scope and quality aspect for the
Bachelor of Mechanical Engineering (Automotive) awarded’

Signature

:…………………………………………………………

Supervisor Name 1

:…………………………………………………………

Date

:…………………………………………………………

Signature

:…………………………………………………………

Supervisor Name 1

:…………………………………………………………

Date

:…………………………………………………………

DETERMINATION OF SOUND TRANSMISSION CLASS (STC)
FOR UTEM LECTURE ROOM

ZAINORDIN ZHAFRAN BIN ZULKEFLI

This Report is to fulfill course evaluation
In
Bachelor of Mechanical Engineering (Automotive)

UNIVERSITI TEKNIKAL MALAYSIA MELAKA
FACULTY OF MECHANICAL ENGINEERING

MARCH 2008

CONFESSION

“I admit this report is my own work except for the summary and passage
which each of it already been explained it source”

Signature

:

Name of the Writer

: ZAINORDIN ZHAFRAN BIN ZULKEFLI

Date

: 27/03/2008

ii

DEDICATION

Thanks to ALLAH S.W.T because with His blessings, I manage to finish
this report according to the dateline.
I dedicate this report to
my beloved family who has always supported me in my whole life.

iii

ACKNOWLEDGEMENT

Alhamdulillah thanks to Allah, with His blessing I manage to complete this

report in time.
I would like to thanks my supervisor Dr JANATUL ISLAH MOHAMMAD
for her guidance and encouragement during completing this report.
I also want to thank to my parents and all my friends for their support and
encouragement to finish this report. Hopefully, this report will become a reference
and the guideline to other students in the future.

iv

ABSTRAK

Tujuan projek ini adalah untuk menjalankan satu ujikaji atau proses
pengukuran dengan tujuan untuk menentukan tahap-tahap tranmisi (STC) dalam bilik
kuliah 3 dan bilik kuliah 4 Universiti Teknikal Malaysia Melaka (UTEM) kampus
Industri.Selain itu,projek ini juga bertujuan untuk mencari kaedah-kaedah yang boleh
menambahkan keselesaan suasana akustik didalam bilik kuliah atau kelas bagi
meningkatkan kualiti pembelajaran dan pendidikan didalam bilik kuliah.Projek ini
akan menyiasat samada bilik kuliah di UTEM memenuhi standart yang ditetapkan
oleh ANSI / ASAS12.60-2002 bagi tahap-tahap akustik didalam kelas atau tidak.Ini
adalah penting kerana andai standart ini tidak dicapai,maka suasana pembelajaran

didalam kelas akan tergangu dan seterusnya akan merosotkan pencapaian pelajar dan
interaksi antara pelajar dan guru akan terjejas.

ii

ABSTRACT

The purpose of this project is to carry out a measurement process in order to
determine the sound transmission classes (STC) in classroom 3 and 4 in UTEM
Campus Industry, besides that this project aims to find a solution to improve the
quality of learning and teaching in UTEM classroom based on the measurement of
the acoustic level in UTEM classrooms. This project is to determine whether UTEM
classroom meet the ANSI/ASAS12.60-2002 Classroom Acoustic Design Standard.
This project will estimate the speech intelligibility in UTEM classroom in order to
improve learning and study environment. The project is important because if the
sound transmission classes did not meet the sound transmission classes’ standard this
will affect the learning environment and lower the activity between teacher and
student.

iii

TABLE OF CONTENT

TITLE

PAGE

CONFESSION

ii

DEDICATION

iii

ACKNOWLEDGMENT

iv

ABSTRACT

v

ABSTRAK

vi

TABLE OF CONTENT

vii

LIST OF FIGURE

ix

LIST OF TABLE

x

CHAPTER 1

INTRODUCTION
1.1 Background of The Project

1

1.2 Problem Statement

2

1.3 Objective

3

1.4 Scope

3

1.5 Project Planning

4

1.6 Report Structure

6

iv

CHAPTER 2

THEORY OF SOUND TRANSMISSION
2.1

Introduction

7

2.2

STC Rating

9

2.3

International Standard to Determine

12

Sound Transmission Classes (STC)
2.3.1 ASTM E413-73 Standard

12

2.3.2

ANSI/ASA S12.60–2002 Standard

13

2.4

Implication for School Design

15

2.4.1

Background Noise From External Sound Sources

15

2.4.2

Pass through Noise from Adjacent Spaces

15

2.4.3

Background Noise From Sources Within Room

17

2.5

Classroom size, proportion and sound absorption

18

2.6

Four Criteria Influence The Speech Intelligibility

20

2.7

Interior Noise Sources

23

2.8

Exterior Noise Sources

27

2.9

Sound Reinforcement

28

v

CHAPTER 3

CHAPTER 4

RESEARCH METHODOLOGY
3.1

Introduction

30

3.2

Measurement Methodology

31

3.3

Equipment

38

3.3.1

RION sound level meter model NA 28

38

3.3.2

Thunder loudspeaker

39

3.3.3

Low cost curtain

40

MEASUREMENT RESULT AND DISCUSSION

4.1

Introduction

41

4.2

Measurement Using Real Ongoing Lecture condition 42

4.3

Measurement No Ongoing lecture Condition

51

4.3

Measurement Using Curtain as acoustic Treatment

60

4.5

Discussion Of the Result

69

4.5.1 Importance of the results obtained

71

4.6

72

Implication of the result

CHAPTER 5 CONCLUSIONS AND FURTHER WORK
5.1

Conclusions

73

5.2

Further work

74

REFERENCE

75

APPENDIX

78

BIBLIOGRAPHY
vi

LIST OF FIGURE

FIGURE
Figure 1: Sound /Surface Interaction: (a) Transmission,

PAGE
8

(b) Absorption, (c) Reflection, (d) Diffusion
Figure 2: Comparison of classroom acoustical environment

14

Figure 3: Sources of background noise in an unoccupied classroom

16

Figure 4: Reverberation

19

Figure 5(a): Noise Reduction between two spaces by a dividing wall

21

Figure 5(b): Noise Reduction between two spaces by a dividing wall

21

Figure 6: Signal-to-noise ratio (SNR)

22

Figure7: Figure 7.Gypsum Board Wall Construction

24

Figure 8: Door Layout Paths

26

Figure 9: Sound Travels over the partition wall

29

Figure 10: Block Diagram of Measuring Data when Classroom 4 is Empty

33

Figure 11: Measurement Location Map for condition i

34

Figure 12: Measurement Location Map for condition ii

35

Figure 13: Measurement Location Map for condition iii

36

Figure 14: This picture is taken in classroom

37

Figure 15: This picture is taken in classroom

37

Figure 16: Sound level Meter (SLM)

38

vii

Figure 17: Thunder loudspeaker

39

Figure 18: Low cost curtain for acoustic treatment test

40

Figure 19: Graph point 1(ongoing lecture condition)

43

Figure 20: Graph point 2(ongoing lecture condition)

45

Figure 21: Graph point 3(ongoing lecture condition)

47

Figure 22: Graph point 4(ongoing lecture condition)

49

Figure 23: Graph comparison between 4 locations for ongoing lecture
Figure 24: Graph point 1 (Test)

50
52

Figure 25: Graph point 2 (Test)

54

Figure 26: Graph point 3 (Test)

56

Figure 27: Graph point 4 (Test)

58

Figure 28: Graph comparison between 4 locations for test condition

59

Figure 29: Graph point 1 (Treatment)

61

Figure 30: Graph point 2 (Treatment)

63

Figure 31: Graph point 3 (Treatment)

65

Figure 32: Graph point 4 (Treatment)

67

Figure 33: Graph comparison between 4 locations (Treatment)

68

viii

LIST OF TABLE

TABLE

PAGE

Table 1: STC Value for Walls

11

Table 2: Data sound level meter measurement for Lecture Situation point 1

42

Table 3: Data sound level meter measurement for Lecture Situation point 2

44

Table 4: Data sound level meter measurement for Lecture Situation point 3

46

Table 5: Data sound level meter measurement for Lecture Situation point 4

48

Table 6: Data sound level meter Measurement No ongoing lecture point 1

51

Table 7: Data sound level meter Measurement No ongoing lecture point 2

53

Table 8: Data sound level meter Measurement No ongoing lecture point 3

55

Table 9: Data sound level meter Measurement No ongoing lecture point 4

57

Table 10: Data sound level meter measurement (Treatment) point 1

60

Table 11: Data sound level meter measurement (Treatment) point 2

62

Table 12: Data sound level meter measurement (Treatment) point 3

64

Table 13: Data sound level meter measurement (Treatment) point 4

66

Table 14: The highest SPL data from sound level meter measurement at a

69

frequency 200Hz for the ongoing lecture classroom condition
Table 15: The highest SPL data from sound level meter measurement is at a

70

frequency 500Hz for the test and treatment condition

ix

LIST OF APPENDIX

NO

TITLE

PAGES

A

Sound level meter data for ongoing lecture measurement

78

B

Sound level meter data for no ongoing lecture

79

x

1

CHAPTER 1

INTRODUCTION

1.1 Background of the Project
The amount of airborne sound blocked from transmitting through a partition is
measured in a Sound Transmission Class (STC) rating. A higher STC rating will
allow sound transmission through walls and increase the background noise level in
the space, degrading the ability to hear and understanding speech [1].
The purpose of this classification is to provide a single-figure rating that can be
used for comparing partitions for UTEM classroom. The rating is designed to
correlate with subjective impressions of the sound insulation provided against the
sounds of speech, sound receiver and sound sources in a classroom.
Achieving a specific STC rating depends highly on the materials and the
installation methods used. Wall and ceiling assemblies can be specified and detailed
to meet a required STC rating. Background noise is a major concern in learning
facilities. STC ratings will help to limit the background noise levels within a space
(depending on the effect of sound transmission on the background noise level). It
may be necessary to increase a required STC rating in order to meet a specified
background noise level requirement.

1.2

Problem Statement

2

A sufficient level of acoustics quality in classroom or lecture room is important
in order to provide effective learning and teaching environment. However if acoustic
level in classroom does not meet the ANSI/ASAS12.60-2002 Classroom Acoustic
Design Standard then this will disturb the speech intelligibility in classroom and
reduce the interaction between teacher and students.
Some of the disadvantaged arise if the ANSI/ASAS12.60-2002 Classroom
Acoustic Design Standard does is not met are as listed below:
a) Students do not understand what the teacher says and this will reduce the
communication between students and teacher.
b) Students lose their focus in class and this will reduce the quality of studies
and produce bad results during assessment.
c) Overall results among UTEM’s students will badly affected because the
university is failed to meet the standards for acoustic requirement.

1.3

Objectives

3

The objective of this project is to carry out a measurement process in order to
determine the sound transmission classes in a selected number of UTEM classrooms.
Besides that, this project aims to evaluate some tests made to the existing classroom
to improve the quality of learning and teaching in UTEM classrooms. If the standard
is not met by existing classroom, some suggestions to improve the quality of learning
and teaching in UTEM classrooms will be discussed as well.

1.4 Scope
The scope for this project is to determine whether UTEM classroom meet the
ANSI/ASAS12.60-2002 classroom Acoustic design Standard or not. This project
involves field measurement in order to determine the acoustic data for Sound
Transmission Classes (STC), as well as to estimate the speech intelligibility in
UTEM classrooms.

1.5

4

Project Planning

Gantt Chart PSM1
ACTIVITIES
TITLE CONFORMATION
OBJECTIVE & SCOPE
PROBLEMS
STATEMENT
LITERATURE REVIEW
METHODOLOGY
CONLUSION
SUBMIT DRAFT
REPORT
SUBMIT FULL REPORT
PRESENTATION

1

2

3

4 5

6

7 8

WEEK
9

10

11

12 13 14

15

16

5
Gantt chart PSM 2
ACTIVITIES

LITERATURE REVIEW
MEASUREMENT
RESULT
ANALYSIS
DISCUSSION
CONLUSION
SUBMIT DRAFT
REPORT
SUBMIT FULL REPORT
PRESENTATION

1

2

3 4 5

6

7

8

WEEK
9
10

11

12

13 14

15

16

6
1.6 Report Structure
Chapter 1 presents the introduction of the project that will include the background,
problem statement, scope and overall project.
Chapter 2 discusses about the previous studies on sound transmission classes, theory on
sound transmission classes, international measurement standard for sound transmission
classes and basic acoustic knowledge. This chapter also discusses the implication of
school design, reverberation, evaluating speech intelligibility, sound reinforcement and
noise criteria rating.
Chapter 3 discuss the project implementation of determine sound transmission classes,
equipment in measurement, previous measurement method and chosen method of
measurement for this project.
Chapter 4 presents the result and discussion of the measurement justifies the validity of
the data taken.
Chapter 5 discusses the conclusions of the project As well as lists some recommendation
for further work.

7

CHAPTER 2

THEORY OF SOUND TRANSMISSION

2.1

Introduction
Intensity is a physical measurement of a sound wave that relates to how loud a

sound is perceived to be. We can also measure the frequency of a sound wave, which
we perceive as pitch. For example, on a piano, the keys to the right have a higher
pitch than those to the left. If a sound has just one frequency, it is called a pure tone,
but most everyday sounds like speech, music, and noise are complex sounds
composed of a mix of different frequencies. The importance of frequency arises
when a sound wave encounters a surface: the sound will react differently at different
frequencies. The sensitivity of the human ear also varies with frequency, and we are
more likely to be disturbed by medium-to high-frequency noises, especially pure
tones [2].
Think of sound as a beam, like a ray of light, passing through space and encountering
objects as shown in figure 2. When sound strikes a surface, a number of things can
happen, including:
Transmission-- The sound passes through the surface into the space beyond it, like
light passing through a window.
Absorption-- The surface absorbs the sound like a sponge absorbs water.

8
Reflection-- The sound strikes the surface and changes direction like a ball bouncing
off a wall.
Diffusion-- The sound strikes the surface and is scattered in many directions, like
pins being hit by a bowling ball.
As a result, the reflected wave will not be as loud as the initial wave. The
frequency of the sound also makes a difference. Many surfaces absorb sounds with
high frequencies and reflect sounds with low frequencies. The Absorption
Coefficient and NRC (noise reduction coefficient) are used to specify the ability of a
material to absorb sound.

Figure 1: Sound /Surface Interaction: (a) Transmission,
(b) Absorption, (c) Reflection, (d) Diffusion
(Source: University of Kansas Architectural Engineering faculty 1998)

9
2.2 STC RATING
Many educators feel it is important to improve acoustics in classrooms used
by students because less than acoustically optimal conditions in the classroom affect
the academic performance of all students. Many experts believe that students miss up
to 33 percent of the oral communication that occurs in the classroom and this will
reduce the quality of learning [3]. Because of that many educator and experts in
universities have has done a research to find the best solution to this problem.
The control of noise from one room to another is a major challenge in
acoustics. Different materials transmit more or less sound at different frequencies. In
transmission, blocking the entire speech range is important, and this factor is
reflected in the STC rating (Sound Transmission Class) of a wall [3]. Critical to
sound transmission issues is the background noise in the receiving room. If the
background noise is higher than the amount of sound passing through (and around)
the wall, then users will not hear the sound from the adjacent room. If background
noise is lower than transmitted noise, then room occupants will hear sounds from the
adjoining space.