Acoustic Analysis of S.M.A.T 2-In-1 Lecture Theatre

ACOUSTIC ANALYSIS OF S.M.A.T 2-IN-1 LECTURE THEATRE

IN

THE FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE.

COMPILED BY

OTABOR OSARUMEN

ARC/09/7424

SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF BACHELOR OF TECHNOLOGY (B-TECH) DEGREE IN ARCHITECTURE

TO

THE DEPARTMENT OF ARCHITECTURE,

SCHOOL OF ENVIRONMENTAL TECHNOLOGY,

FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE.

Lecturer: Prof. Olu Ola Ogunsote APRIL 2014

TABLE OF CONTENT

1. 0 INTRODUCTION
2. ACOUSTICS AND ARCHITECTURE
3. JUSTIFICATION FOR THE STUDY OF ACOUSTICS

CHAPTER ONE

2.0ARCHITECTURAL ACOUSTICS IN LECTURE THEATRES

CHAPTER TWO:

3.0 BUIDING DESCRIPTION

3.1 LOCATION

3.2 ARCHITECTURAL DESIGN

3.3 FINISHING MATERIAL

3.4 FACTORS AFFECTING ACOUSTICS

CHAPTER THREE:

4.0SOURCES OF INTERNAL AND EXTERNAL NOISE IN 2-IN-1 LECTURE THEATRE

CHAPTER FOUR:

5.0PERCEPTUAL ASSESSMENT OF THE ACOUSTIC CHARACTERISTICS OF THE 2-IN-1 LECTURE THEATRE

6.0REMEDIAL ACTIONS

REFRENCES

ABSTRACT

The study being carried out on the S.M.A.T 2 I 1 Lecture theater aims at giving a full acoustic description of the hall in of the: Sources of noise into the building, the kinds of materials employed in the construction of the building and the way these materials perform in acoustic terms. Ways of improving the acoustics of the building are also to be suggested based on the aspects mentioned above.

1.0INTRODUCTION

ACOUSTICS is simply the physical quality of a space for performing music, which involves mainly the study of the room acoustics and the control of noise; While ROOM ACOUSTICS is concerned with the nature, properties and characteristics of sound in an enclosed space,NOISE is simply an unwanted or damaging sound that interferes with what people are trying to do or sound, which has an adverse effect on health or safety.

In order to be able to deal with the problems of noise in the Small Lecture Theatre, it would be paramount to carryout an analysis of the nature, causes and effects of the noise. These findings coupled with the knowledge of basic acoustics (the nature of sound and its physical properties.) will be of significant importance in solving the noise related problems in the hall hence providing a more conducive learning environment for the users.

1.1ACOUSTICS AND ARCHITECTURE (acoustics in buildings)

The question of acoustics in lecture halls has been researched internationally in recent years. Mackenzie, for example investigated the influence of poor acoustics on the students and lecturers, in an important study in 1999.

Of course, good acoustics are important in lecture halls: the background noise must be minimized and the room form and materials must be designed to support the acoustics in order to provide high speech intelligibility.

1.2JUSTIFICATION FOR THE STUDY OF ACOUSTICS

The study of acoustics in relation to buildings is necessary to incorporate the knowledge gained into the early stages of design in other to achieve the following:

To create an acoustic friendly environment for all users including hearing impaired individual.

To ensure maximum correspondence between individuals in an enclosed space without disturbance form internal or external source of unwanted sound or noise.

To reduce to barest minimum the physiological and psychological effects of noise on humans in the designed spac

CHAPTER ONE

2.0 ARCHITECTURAL ACOUSTICS IN LECTURE THEATRES

The use of a space is one of the main factors which influence its acoustics. The lecture theatre is an example of a single performance space. It is an auditorium meant for speech alone and as such, the individual speech sounds should be sufficiently distinguished for a speaker to be readily understood. In spaces like these, it is relatively easy to achieve acoustic excellence because the design can be focused around a single type/source of performance.

Acoustic excellence in a lecture theatre could be obtained by attaining very low levels of background noise, which may go unnoticed by most people, but reduces their experience, reducing clarity of sound. Studies have shown that a reduction in background noise significantly reduces audience noise and eliminates the need for amplification of sound i.e. increasing signal strength. When a lecture theatre is truly quiet, the speaker can use his entire dynamic range and still be heard from every part of the building.

Before 1895, when a physicist William Clement Sabine was instructed by the corporation of Harvard University to remedy the acoustical difficulties of the lecture room of the Fogg Art museum, no actual quantitative measures had been brought to bear on characteristics of sound such as reverberation, absorption, and sound transmittance. Sabine spent two years experimenting on the Fogg lecture room and permanent changes were made. From this time there followed a vocation for a new branch of physics; architectural acoustics.

In recent times, the importance of reducing noise levels has resulted in the development of rules or guidelines stating the acceptable noise levels in different spaces. The problem of acoustical problems in existing theatres has resulted in more demand for acoustic planning in lecture theatres.

Fig 1a: Alumni Hall Carnegie Mellon University

An example is the Carnegie Mellon University alumni hall shown above, which was originally built by Andrew Carnegie as an art gallery. It was plagued with acoustical problems and while it was required to incorporate modern acoustic design it was also required that the room’s historic heritage be preserved. As a solution, sound dispersing maple shells were used, which complemented the restored hardwood floors. A skylight constructed of lexan pyramids retains original day lighting and eliminates harsh echoes.

Another case study to show the effects of acoustic planning is the Plum High School Auditorium in Plum PA. The acoustic planning was done by the sextant group. The goal was to provide a natural acoustic environment that minimized the need for sound reinforcement, at the same time preserving the structural and aesthetic vision as conceived by the architect.

Fig 1b: Interior views of the plum high school auditorium showing stage and balconies

To accommodate 1700 seats, a large balcony had been designed which cast a significant acoustic “shadow,” compromising the ability to hear in back rows. The original room geometry also created a significant delay between direct and reflected sound, creating a disconcerting slap-echo that further interfered with performances.

Sophisticated 3-D computer modelling was used to measure anticipated reflections and calculate delays. Interactions between architectural space, surface and sound were considered, adjusted and defined, revealing significant design opportunities that the architect was able to take advantage of. Adjustments to the balcony positioning led to dramatic improvements in the room acoustics. Further improvements came through strategic placement and angling of specially designed, acoustically reflective ceiling clouds, carefully chosen wall structures and surface treatments.

Today, even in the back row, one can hear the natural sound of a single voice from the stage, with minimal need of amplification or reinforcement. From an acoustic perspective, it is almost as if every one of the 1700 seats is now “the best seat in the house.

CHAPTER TWO

SMAT 2 in 1 LECTURE THEATRE,

F.U.T.A Akure, Ondo State.

3.0 BUILDING DESCRIPTION

The SMAT 2 in 1 lecture theatre is an approximately 1200 -Seater Lecture (speech) auditorium, which was commissioned on the 19th of November 2010. It was designed for use as lecture hall for students and also encompasses of 2 approximately 600 seater lecture and offices for lecturers of the Federal University of Technology, Akure, Ondo State.

3.1LOCATION

The SMAT 2 in 1 LT. is located at the Obanla Section of the University campus; encompassed and surrounded by different school buildings on all sides.

Bounded in the by the School of Environmental Technology (S.E.T) building, the School of Earth and Mineral Science (S.E.M.S). The lecture is used by both schools alongside the School of Management Technology (S.M.A.T) and encompasses two lecture theaters, offices, conveniences and stores.

3.2ARCHITECTURAL DESIGN

The S.M.A.T 2 in 1 LT. is designed as a bungalow; it functions presently as a lecture hall for all students according to their fixed lecture hours, accommodating ideally at most 200 students at a time.

The building consists of the two lecture theaters, offices, conveniences, stores and toilets.

The external dimension of the building is approximately 63.4m x 25mm long; its headroom is approximately 4.5m, it design is such that the seating area steps downwards three times towards the stage or lecture front, giving the hall something of a theatrical effect. The stage is raised 0.4m above floor level.

The main halls are accessible from all three sides each, mirroring each other with the offices, a passage and stores in the middle

.

3.3FINISHING MATERIALS

The construction materials used for the various components are as follows

Walls

The walls are of plastered sand Crete hollow block with a textured paint finish.

Ceilings

The ceiling is made from simple or the commonly used P.V.C

Floors

The floor of the seating area is finished with glazed ceramic tiles; the stage is a raised to a hight of 300mm covered with the same floor material.

The picture shows the stage floor and part of the seating area.

fenestration

All the doors are made of steel,(Iron monger).While glass louver blades are used for the windows

FACTORS AFFECTING ACOUSTICS

The factors that affect acoustics of an auditorium include its size, shape nature of materials and finishes, acoustic zoning etc. in attempting to analyse the acoustic performance of a building all these must be considered.

SIZE AND SHAPE.

This can greatly influence acoustic condition. According to Orpheus acoustics, one of the reasons why many spaces have terrible acoustics is that they are just too big. This is mainly because the reverberation time increases with the size of a room and depending on the size, the reverberation time could rise above acceptable limits.

The area of theS.M.A.T 2 in 1 LT is approximately 568.7sq m. with a ceiling height of 4500mml. It has an almost rectangular shape as the plan shows.

FINISHES.

The materials used in the finishing of a building can greatly determine its acoustic performance. In lecture theatres, it is advisable to use sound absorbent materials for the finishing. Effect of finishes on acoustic performance should be considered when choosing finishes for the main surfaces of the room i.e. the wall, floor and ceiling.

FENESTRATIONS.

The materials used for the windows and doors and the framing system in the building are also a determinant of the overall acoustics condition of the building. For the 2 in 1 LT, glass louver blades windows of 6mm thick are used. These windows which are always opened for ventilation allow for the entry of external noise as against a double glazed window with insulation and closed always. On the other hand, metal panelled doors with poor sound absorbing properties are used. These doors and method of installation (with gaps) reduce the acoustics of the building.

CHAPTER THREE

4.0 SOURCES OF INTERIOR AND EXTERNAL NOISE IN S.M.A.T 2-IN-1 LECTURETHEATER

Noises from both interior and exterior sources come together to make up what we know as background noise. This is the normal prevailing ambient noise from many sources including street traffic and outdoor noises in general. It also includes noise from mechanical equipment, adjoining rooms and even noise from the audience itself.

The sources of noise 2 in 1 LT consist of the following;

OUTDOOR NOISE

The sources of outdoor noise at the ETF include

• Street traffic (vehicules): this includes vehicular noises from surrounding streets and car parks e.g. the S.M.E.S and S.E.T car park - road.

• Street traffic (pedestrian) and circulation in walkways: THE 2 in 1 LT is surrounded by walkways leading to the S.E.M.S phase 2 building, S.E.M.S extension. These walkways experience heavy traffic during lecture hours and the associated noise levels during the day.
• Mechanical noise from telecommunication generator: There is a telecommunication mast at the back of the 2 in 1 LT almost opposite the School of Environmental Technology. Once the power supply is interrupted the generators come and it produces a lot of noise causing increased external noise levels.

INDOOR NOISE

The sources of indoor noise at the 2 in 1 LT include

• Audience noise: during lectures when the main halls are packed to full capacity there is usually a lot of audience noise. This is beyond the direct control of the architect or acoustician. However research has shown that audience members are significantly quieter when background noise is very low.
• Circulation noise: this is noise due to the movement of people around the hall, the effects of circulation noise in the 2 in 1 LT has been reduced by careful zoning. It can further be reduced by using an absorptive floor covering e.g. carpeting.
• Fan noise: this results from intake turbulence and vortex generation in relation to fan geometry and rotational speed. The fans at the 2 IN 1 produce a continuous noise which though it may go unnoticed by most people will diminish their hearing experience.
• Noise from furniture: the poor lubrication of the metal frames of the furniture result in scraping and creaking noises from the parts bearing on each other.

CHAPTER FOUR

5.0PERCEPTUAL ASSESSMENT OF THE ACOUSTIC CHARACTERISTICS OF THE 2 in 1 LECTURE THEATRE

In the few years that the 2 in 1 LT has been in use, it has served its purpose without any serious complaints from its users but this may be as a result of the fact that most of us are already accustomed to low standards in our environment or country.

All halls or large empty spaces have differing acoustic properties when full and when empty. This is the same with the 2 in 1 LT.

When empty a loud voice from the stage can be heard all over the hall with diminishing intensity as one progresses farther away from the source. This is mainly because at such times there is no audience or circulation noise. On the other hand when the hall is full, sound is absorbed by human bodies causing the intensity to diminish rapidly with increased distance from the source. Fortunately the tiered seating arrangement or the raking with its main intention for visuals provides a means for sound to travel directly from source to receiver without coming against a barrier.

Due to the poor acoustic nature of the floor finish, any circulation or movement that involves impact on the floor results in a disturbing emission of noise, this can be quite disturbing during lectures especially when coupled with audience noise. Most times the listener has to strain in order to hear.

The lack of adequate lubrication on the metal components of the furniture leads to annoying creaking noises whenever weight is put on the seats, also some of the furnitures are already damaged and even make louder. The movable seats in the chairs usually slam hard whenever weight is removed from them; this produces a jarring sound whenever it occurs.

During lectures, external noise sources such as circulation of people around the building, circulation and waiting at the entrances and balcony also result in disturbing noise levels. Street traffic and especially noise from the S.E.M.S car park can be particularly disturbing. The telecommunication generator the back of the hall is another source of noise disturbance it is rather loud and interferes with one’s ability to concentrate.

For best acoustic qualities rooms are usually designed to produce sufficient reflections for naturalness, without introducing excessive reverberation at any frequency, and without echoing certain frequencies unnaturally. An appreciable reverberation time improves acoustical effect; a loud sound should still be barely audible for one to two seconds after the sound has stopped in an auditorium.In the 2 in 1 the echo of sound is not physically discernible to the human ear neither can the reverberation time be determined without appropriate apparatus. However, by careful listening it can be perceived that there is no excessive reverberation or echoing though the phenomenon is present.

6.0REMEDIAL ACTIONS

The acoustic environment of this church is not favorable but can be improved. If necessary remedial actions are taken, certain factors can be avoided and as such can better the acoustics of the church and its environment. In order to limit the effects of external noise, the building can be moved from the main road away from the noise from traffic, the motor park etc., but this would be difficult as either the existing church would have to be demolished and rebuilt in another area of the site or a new church building constructed.

Below are probable solutions which are more cost effective and if put in place would go a long way at improving its acoustics.

External noise – Since majority of external noise is generated from traffic, pedestrians, generator house and the motor park, which cannot be eliminated, the following actions can be taken in reducing them.

• Creating a buffer zone between the roads and the church building i.e. by planting of trees.
• By having recesses on walls, use of fins and hoods. By so doing, the total surface area the sound hits is reduced thereby background noise into the building would have reduced to a bearable extent.
• By isolating the generator house and directing the exhaust opposite the building. The use of perforated walls towards the road and at the back.
• Buy quiet generator to replace the former one in use. The new generator serves the same purpose as the former but quieter.
• Proper maintenance of the existing generator can go a long way at reducing noise generated by it.
• The thickness of the glass can be doubled to reduce the amount of sound transmitted into the building.

Internal noise – The internal noise can be controlled by using the following measures:

• Ceilings

• Use of acoustic boards for the ceilings.
• Flat ceilings distribute sounds evenly better than curved ceilings; flat ceilings should be made use of.
• For aesthetics purpose, use of paints that are rough and can diffuse sounds evenly should be used to finish the board.
• Suspended ceilings of acoustic boards should be used to cover the slabs.
• Use of cover fillets and ceiling noggins that can absorb sound should aolso be adopted.
• Walls

• The use of texcote paint which makes the surfaces of the walls rough and help in diffusing sound better as against gloss and emulsion paint.
• The walls should be cladded with acoustic boards or timber panels.
• Circular columns can be used instead of octagonal columns
• The columns can be cladded with acoustic boards and timber panels
• The edges of the beam and columns can be chamfered

REFERENCES