A

TERM PAPER

ON

ACOUSTICS ANALYSIS

OF

DIGITAL RESEARCH AND RESOURCE SHARING CENTRE

PREPARED BY

ADEYANJU A.S (ARC/08/3969)

ODUNIYI M. A (ARC/09/7401)

ABSTRACT

This report details the acoustic analyses of the digital research and resource sharing centre. The report identifies the major noise sources within and around the building. The report analyses the basic finishing materials of the building (digital research and resource sharing centre) components (walls, floors and ceilings). The materials used for the construction of these building components were also analysed in respect to their acoustic properties; such as how they absorb and reflect sound. Basic noise sources were identified and detailed via photographs and computer aided design. A decibel scale was used to measure noise levels at the source both internally and externally. Methods of improving the acoustic of the building were highlighted.All data used in this report were gotten through field work.

INTRODUCTION

The digital research and resource sharing centre is located at Obanla campus of the federal university of technology Akure. The building is opposite the university’s chapel and is adjacent to the university library. The building basically comprises the computer science study laboratories and offices for staff.The study laboratories are rectangular in shape and they are cross ventilated.

ANALYSES OF THE BUILDING

The floor finish used in the building(Digital research and resource sharing centre) is vitrified tiles. Vitrified tiles do have poor acoustic properties. Vitrified tiles due to its hard and solid nature do not easily absorb sound rather it reflects the sound back at the same angle as the incident sound ray thereby causing reverberation of sound. Vitrified tiles generate noise when walked on. Often times the noise generated is annoying and disturbing.

Plate 1.0: showing interior floor finish

Source: Author’s archive (2014)

The wall of the building is sandcrete block finished with emulsion paint. The wall of the building has verypoor acoustic characteristics. The wall of the building is hard and solid and the wall finish (emulsion paint) does not absorb sound. Although the rectangular shape of the building is a good form when it comes to reducing the effects of reverberation of sound. Sandcrete block wall finished with emulsion paints often reflects sound rather than absorb sound.

Plate 2.0: showing walls finished with emulsion paints

Source: Author’s archive(2014)

The material used for the ceiling is polyvinyl chloride (PVC). The ceiling is aesthetically sound but polyvinyl chloride, when used in the manufacture of ceiling tiles has a poor acoustic properties. It does not readily absorb sound. Ceiling tiles made with Polyvinyl chloride reflects sound at the same angle as the incident sound ray. Although not all the sound is reflected some is been absorbed.

Plate 3.0: showing polyvinyl chloride ceiling tiles

Source: Author’s archive (2014)

EXTERNAL NOISE SOURCES

There are several external noises generated around the building. The major external noise sources are:

  1. Vehicular noise
  2. Generator noise
  3. Air-Condition noise
  4. Human noise

Fig 1.0: Showing site plan of the building

Source: Author’s archive (2014)

Fig 2.0: Showing floor plan of the building

Source: Author’s archive (2014)

Fig 3.0: Showing roof plan

Source: Author’s archive (2014)

Fig 4.0: showing section thoroughly worked on

Source: Author’s archive (2014)

Fig 5.0: Showing ceiling plan

Source: Author’s archive (2014)

Plate 4.0: Showing approach view

Source: Author’s archive (2014)

Plate 5.0: Showing rear view

Source: Author’s archive (2014)

Plate 6.0: Showing left elevation

Source: Author’s archive (2014)

Plate 7.0: Showing right elevation

Source: Author’s archive (2014)

Plate 8.0: Showing the building interior

Source: Author’s archive

Plate 9.0: Showing the building interior

Source: Author’s archive (2014)

ANALYSES OF SOURCES OF EXTERNAL NOISE

External noise sources are devices or machineries located outside the building that generates noise to the building. Sometimes, people talking frivolously outside the building can also contribute to the production of the total external noise generated. In the building surveyed, the major external noise sources are;

  1. Vehicular noise: the noise produced from engines and exhausts of vehicles moving around the building can be termed vehicular noise. The noise is often annoying and can make people uncomfortable. Noises of very high decibel are also produced from the horns of these vehicles

Plate 10.0: showing a moving vehicle Plate 11.0: Showing a generator Source:Author’s archive (2014) Source: Author’s archive (2014)

  1. Generator noise: noises produced from generators are often termed generator noise. In the building surveyed, the generator set was placed only about a metre away from the building. The closeness of the generator to the building produces a very high level of discomfort to the users of the building.
  2. Air-Condition noise: The noise generated from the air-condition system is termed air-condition noise. Noises from air-condition systems seems insignificant but when the noise is measured it goes a long way. These noises are among the major external noises of the building surveyed.
  3. Human noise: Frivolous conversation among people outside the building can constitute external noise. It was quite evident from the survey that people talking carelessly at the top of their voice produces a high level noise that can cause disturbance and make users of the building uncomfortable.

ANALYSES OF SOURCES OF INTERNAL NOISE

Internal noise sources are devices or machineries located inside the building that generates noise within the building. Sometimes, people talking or murmuring inside the building can also constitute to the production of the total internal noise generated. In the building surveyed, the major internal noise sources are;

  1. Fan noise: these are noises generated from the rotational movements of the fan blade. At top speed the noise becomes quite evident and disturbing compared to when the fan is at low speed.
  2. Noise from office equipment: these are noise generated from computers, printers and scanners. Although they do not produce high level noise but when they become old and faulty they can produce high level noise.
  3. Noise from air condition systems: these are noises produced from the air-condition unit. They seem insignificant but when the air-condition unit becomes old the noise they produce may become worrisome.
  4. Human noise: People talking, murmuring and whispering within the building may produce moderate amount of noise that may become unpleasant.

Plate 12.0: showing a ceiling fan Plate 13.0: Showing an A/C unit

Source: Author’s archive (2014) Source: Author’s archive (2014)

ASSESSMENTS OF THE BUILDING ACOUSTIC CHARACTERISTICS

The acoustic characteristics of the building was assessed under the following

  1. Reverberation: reverberation is the persistence of sound after its source has stopped. (Source: lecture note series). The acoustic property of the building section surveyed was very poor in relation to reverberation. The wall finishes have very poor acoustic properties, the floor finish is hard and solid, and the ceiling tiles are not perforated. The furnitureused in the laboratory is made of hard woods which absorb very little fractions of the total sound produced. When a speech is made in that section of the building (computer science study laboratory one), it will take a long period of time before the sound becomes inaudible even after its source has stopped.
  2. Background noise: The noise produced from cars outside the building section, noise from users of the space and noise from the air-condition unit makes up the background noise. In the building section surveyed the background noise was quite high. These is due to the presence of vehicular movement around the building and the presence of air-condition unit in the space. Frequent whispering from users of the space also contributed to the background noise.
  3. Echoes:Due to the effect of reverberation, continuous sound was heard in the section surveyed after its source has stopped. Echo is the sound that is heard after the sound source becomes inaudible.

MEASUREMENT OF EXTERNAL NOISE LEVELS

S/N / Noise source / Sound in dB
1 / Vehicular noise / 75-80dB
2 / Human noise / 55-60dB
3 / Air – condition noise / 55dB
4 / Generator noise / 75dB

Table 1.0: showing measurement of external noise level

Source: Author’s archive (2014)

MEASUREMENT OF INTERNAL NOISE LEVELS

S/N / Noise Source / Sound in dB
1 / Air- condition / 55dB
2 / Fan noise / 60-65dB
3 / Conversation / 50-55dB
4 / Office/ Office equipment / 45-50dB
5 / Whispering / 30-35dB

Table 2.0: showing measurement of internal noise level

Source: Author’s archive (2014)

METHODS OF IMPROVING THE ACOUSTICS OF THE BUILDING SPACE SURVEYED

  1. All faulty office equipment should be changed
  2. All old office equipment should be replaced with new ones
  3. All new appliances or equipments to be purchased must meet accepted noise standards. Preferably, quiet appliances or equipment should be purchased.
  4. Fan speed should be reduced at all times in order to reduce the noise level
  5. Frivolous conversation and arguments should be avoided within and outside the building.
  6. Thick carpets should be used as floor finish
  7. Walls should be covered with thick curtains that can absorb noise
  8. Soft perforated ceiling tiles should be used
  9. The generator should be located at a reasonable distance from the building
  10. Air –condition units should be cleaned and serviced at regular intervals. This is because dust can cause friction and this may cause noise when in use
  11. Shrubs should be planted to serve as a barrier against direct vehicular noise
  12. The generator should be placed on a soft terrain in other to reduce vibration between the generator and the concrete floor.

CONCLUSION

The space surveyed and the entire building has a very poor acoustic characteristics. Architects should acquaint their clients with sustainable building materials with good acoustic properties. Where necessary, architects should specify quality materials or equipments that have good acoustic characteristics. Architects should indicate from the site plan the exact placing of equipments so that equipment with the same noise level should be placed together. Architects should also specify quality finishing materials with good acoustics characteristics.

REFERENCE

  1. “Lecture note series on acoustics”

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