Arc 507: Acoustics and Noise Control

ARC 507: ACOUSTICS AND NOISE CONTROL

AN ACOUSTIC ANALYSIS CARRIED OUT ON THE BLOCK OF CLASSROOMS AND OFFICES (GNS BUILDING) OF THE FEDERAL UNIVERSITY OF TECHNOLOGY AKURE.

BY

ARC/09/7413 OLALEYE OMODOLAPO OLUWASEYE

ARC/09/7416 OLUMIDE G.O

SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF BACHELOR OF TECHNOLOGY IN ARCHITECTURE.

TO

THE DEPARTMENT OF ARCHITECTURE

SCHOOL OF ENVIRONMENTAL TECHNOLOGY

FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE,

ONDO STATE

NIGERIA

COURSE LECTURER: PROFESSOR OLU OLA OGUNSOTE

JULY, 2014

Cover Page

Table of Contents

1.0Introduction1

1.1 Description of GNS building1

2.0Acoustic Characteristics of Some Selected Phenomena (Design and Finishes).2

3.0Sources of Noise.

3.1External Sources

3.2Internal Source

4.0 Perceptual Assessment of the Acoustic Characteristics of the GNS building

5.0Proposal for the Improvement of Acoustic Situation and Conclusion

5.1Internal Proposal for Acoustic Improvement

5.2External Noise

5.3Conclusion

References

INTRODUCTION

Acoustics is the science of sound. It is an aspect of environmental science that deals with the study of how sound of all sort is generated, transmitted and perceived by humans in the enviroment

This paper takes an analytical study of the acoustic condition of the Block of Classrooms and Offices (Popularly called the GNS Building) of The Federal University of Technology Akure, Ondo State. This is done through a critical look at the design, the floor finishes, wall finishes, ceiling finishes and how they affect the reflection, absorption, transmission, reverberation, and echoes of sound in the space. Also, under critical assessment is the source of internal and external noise in the building and proposal for their effective control in order to achieve adequate intelligibility of sound.

1.1DESCRIPTION OF GNS BUILDING

The GNS BUILDING is located in the academic core of the FUTA Campus close to the school of Environmental Technology (SET), School of Earth and Mineral Sciences (SEMS) and School of Management Technology (SMAT).

The building is flanked on the rear and front by PG lab, phase IIbuilding with proper landscape setback of about 90 meters. The building begun construction immediately after its approval by the Physical Planning FUTA Chapter in 2010 and was completed in 2013.

2.0 ACOUSTICS CHARACTERISTICS OF SOME SELECTED PHENOMENA(DESIGN AND FINISHES).

Architectural surfaces need to be designed to either reflect sound, absorb sound, or diffuse sound.

Texcote paint: Apart from the adverse weather resisting properties of texcote paint. It provides a rough surface which is a very effective means of diffusing sound. Incident sound ray on the external wall is reflected in all directions to some extent.

Emulsion paint on wall: It is a plane surfaced paint used in the interior of the BIG LT. It has the capability of reflecting sound rays incident upon it.

Ceramic floor tiles: As a result of hard surface of the floor finish. There is the possibility for it to reflect incident sound rays.

Direct line of vision: The mode at which the seats are planed gives room for everybody to maintain eye contact with the speaker on the stage. This enhances intelligibility of sound as the direct line of auditory perception is achieved.

3.0SOURCES OF NOISE

In any architecturally designed space, there two type of sources whereby noise can be induced. The GNS BUILDING is not an exception and these sources can broadly be divided into; external sources and internal sources.

This will be discussed in relation to the building under study

3.1EXTERNAL SOURCES

Figure 1Thecarpark

This gives room for students to provide seats for themselves under the shade provided as they for the next lecture. They shout and yell under this covered walkway. Despite this, the fact that the roof pattern for the covering is curvilinear gives a convergent reflection of sound within it and reduces the amount of sound that could go outside it into the space under consideration. Although, it can still be heard faintly as background noise within the building.

Figure showing the left side approach

Ground and Upper floor plan

IN

G

4.0 PERCEPTUAL ASSESSMENT OF THE ACOUSTIC CHARACTERISTICS OF THE GNS BUILDING

This is assessment of the ways in which sound is perceived in the GNS BUILDING.

The following characteristics of sound are discussed;

• Amplitude:

The amplitude of a sound wave is the degree of motion of air molecules within the wave, which corresponds to the changes in air pressure that accompany the wave. The greater the amplitude of the wave, the harder the molecules strikes the eardrum and the sound is perceived.

The use of electronic loudspeakers with amplifiers will increase this amplitude; this is in a dilapidated state in the building.

• Intensity:

It is the average flow of energy per unit area perpendicular to the direction of flows through a gate in a dam. The distance at which a sound can be heard is highly dependent on its intensity. Hence, without a public address system (PAS), the intensity of sound is always very low for the sound to be perceived effectively towards the far end of the classes.

• Background:

This is also known as the ambient noise. It is the average level of sound energy occurring within an architectural environment at a specified time due to various noise sources in and around the space. This has been greatly reduced from external noise source through absorptive property of surrounding vegetation, the reflective properties of the fins used on the window (which shades-off sun and sound rays); the considerable window seal height prevents the sound from entering directly into the building.

Movement of students along the step within the building, the electric fan as it rotates air, are also source of background in the building. This should be controlled effectively.

• Reverberation and Echo:

Reverberation is the persistence of sound in an enclosed space after the source of sound has been put off. It is a property of sound that could affect the intelligibility of sound. Echo is a sharp reflection of sound; obeying the fundamental law that angle of incidence is equal to the angle of reflection. This two characters of sound has been reduced to the barest minimum in the building as they have negligible effect. This as a result of balance in absorption and reflection through the use of material in the building. For example, the mineral fiber ceiling used as a ceiling material is a good sound absorbent material, the partial upholstery of seat, rug used at the stage area --- absorbs sound which is reflected from the walls, floor and other hard materials

5.0PROPOSAL FOR THE IMPROVEMENT OF ACOUSTIC SITUATION AND CONCLUSION

No matter how good or bad a situation might be, there is always room for improvement. In other to further improve the acoustic condition in thebuildingthis section looks into some recommendations which will be considered under INTERNAL AND EXTERNAL RECOMMENDATIONS.

• 5.1INTERNAL PROPOSAL FOR ACOUSTIC IMPROVEMENT

The electric fans:

Regular maintenance need to be carried out on the fans so that it would be properly balanced so as to reduce the background noise that is been generated from it.

Full upholstery of seat:

The seat may be fully upholstered so that the bare timber part can be laid with cushion. This will improve the sound absorption property.

5.2EXTERNAL NOISE

Trees and shrubs:

Planting of more trees and shrubs in addition to the ones presently on site will keep-off background noise the more from the power house and from people discussing outside by absorbing them.

5.3CONCLUSION

Having analyzed the present acoustic situation in the GNS Building, it is note worthy issues to acoustics and noise control in an architectural space cannot be over-emphasized. Most especially, in a facility which is been has been designed for speech, lecture and learning activities.

Acoustic properties of such spaces will be improved through careful selection of floor finishes, wall finishes, ceiling materials, etc. The architectural design of such spaces is also a determining factor of acoustic. Proposals are made to how background noise, reverberation and echo could be reduced to the barest minimum for an improved intelligibility of sound.

REFERENCES

Metric Handbook Part 40 “Sound” pdf.

Microsoft Encarta Premium (2009) “sound”. Physical characteristics.

Stephen Haas and Christopher Jaffe (1999), Time Saver Standard for Architectural Design. Part II “Application”. Pg 108 -109.