Design And Construction Of A Noise Meter / Sound Meter

INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Environmental noise is defined as the noise emitted from all sources except in the industrial workplace. The major sources of environmental noise are roads, rails and air traffic, industries, construction and public works, and the neighbourhood. The extent of the environmental noise problem is very large. In the United States, over 40 percent of the population is exposed to transport noise levels exceeding 55 dB(A), and in the EC and Japan, these percentages are even higher (OEDC, 1993). In contrast to many other environmental problems, noise pollution continues to grow, accompanied by an ever-increasing number of complaints (WHO, 1999). The first principle of the World Health Organization (WHO) Constitution is its definition of health that is given as: “A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.” According to this WHO definition of health, noise impacts such as population annoyance, interference with communication, and impaired task performance are health issues. Noise has a significant impact on the quality of life and is a health problem [1]. The effects of noise are seldom catastrophic and are often only transitory, but adverse effects can be cumulative with prolonged or repeated exposure. Sleep disruption, the masking of speech and television, and the inability to enjoy one’s property or leisure time impair the quality of life. In addition, noise can interfere with the teaching and learning process, disrupt the performance of certain tasks, and increase the incidence of antisocial behaviour. There is also some evidence that noise can adversely affect general health and wellbeing in the same manner as chronic stress [2]. Many are aware that noise management is important. Noise can be a problem at busy times during the day/semester and many students have different expectations with regard to what is acceptable. Library staff strives on a daily basis to manage noise levels and we have introduced many measures in this regard. There is a silent area designated, where talking, texting and the use of audio/laptop devices are prohibited. The bathrooms and back stairwells are designed as phone-friendly areas. For these measures to have an impact, the library users should cooperate noisy behavior themselves or report a disturbance to the library. Libraries are committed to providing the library users with a comfortable learning environment as well as a welcoming atmosphere to all users. So, students and librarians need rooms with quiet learning space so that barriers to learning are removed because Noise can impair or prevent our ability to understand. This means that there is a need to provide a special gadget to control noisy environment to achieve quiet levels so that all students will have clear auditory access to learning in that library.
A sound level meter is simply a device with audio-frequency sensing capabilities that is controlled essentially by a microcontroller in turn measuring, comparing and regulating audio signals all in a bid to reduce noise level in a library as well as maintain a stable audio frequency throughout the library environment. The Sound Level Meter measures sound level in decibels (dB; a logarithmic unit used to measure the sound intensity) and it can be used for activities such as environmental noise studies, sound level comparisons, investigating room acoustics, sound isolation modeling and sound propagation modeling amongst many others [3].
A typical meter consists of a microphone for picking up the sound and converting it into an electrical signal, followed by electronic circuitry for operating on this signal so that the desired characteristics can be measured. Sound meters are usually fitted with a filter whose response to frequency is almost like that of the human ear. A digital Sound level meter was built in this work. Digital displays also allow a wider span to be shown whilst still giving the necessary decibel resolution therefore it is easier (and cheaper) to monitor sound level digitally.

1.2 PROBLEM STATEMENT
Normally, sound intensity up to 30 dB is pleasant. Above 80 dB, it becomes annoying. And if it goes beyond 100 dB, it may affect your psychomotor performance, detracting your attention and causing stress. Noise pollution may also affect your hearing ability. Most place quiet places such as libraries, whilst ensuring that the necessary facilities are available to its users, also seek to provide an atmosphere conducive enough for research, study, and assimilation. However, noise is a major hindrance to achieving such conducive arrangements in our libraries. Therefore, measures need to be taken to help eliminate this problem. This project is aimed at designing and implementing a sound level meter.

1.3 AIM AND OBJECTIVES OF THE STUDY
The main aim of this work is to build a sound level meter circuit that senses and displays the noise intensity level in your room. The objectives of the study are:
i. To build the system prototype
ii. To write and install in microcontroller, a microprogram using MikroC programming language, to enable it to be interfaced with an LCD display for sound level, compare input sound signals to a critical level and send out a signal when it is above the critical level.
iii. To maintain peace and quietness in a library
iv. To maintain good health

1.4 SCOPE OF THE STUDY
The scope of this work covers building a sound level meter is simply a device with audio-frequency sensing capabilities that is controlled, essentially, by a microcontroller, which measures, compares, and triggers the appropriate action (displays the level of noise on an LCD) to reduce noise level once the critical sound level has been exceeded. The sound level meter consists of a Condenser microphone (to convert the sound into electrical signal), Pre-Amplifier (amplifies the electrical signal), Microcontroller (with internal ADC feature – to capture and compare the input signal with a critical value), Play and Record Chip (to play a pre-recorded message, alerting library users of increasing sound level) and LCD display (displays the sound levels). The Sound Level Meter measures sound level in decibels and can be used for activities such as environmental noise studies, sound level comparisons, investigating room acoustics, sound isolation modeling, sound propagation modeling etc.

1.5 APPLICATION OF THE PROJECT
The Sound Level Meter can be applied in several different ways as follows:
 General Purpose: General purpose sound level meters meet the strict international standards. These sound level meters are designed for use in general noise surveys. They are easy to use and give clear results on the built- in LCD display [5].
 Product Testing: Sound level meters are used for testing the noise from products and alarms. These are general purpose sound level meters that are suitable for many product testing applications, such as fire alarms, lawn mowers and other machinery.
 Noise at Work: Sound level meters can be used for measuring noise at work and occupational noise exposure for workers. These sound level meters are designed to meet the demanding requirements and standards of governing regulations. They are designed to be easy to use but still provide you with all the noise measurement parameters that you need in an accurate and reliable manner.
 Environmental Noise: Sound level meters can be used for monitoring environment and community noise levels. These sound level meters are suitable for the measurement of environmental or community noise. This can be noise coming from factories, road traffic or noisy residents. All these meters are hand-held and battery powered and some could have weatherproof cases and microphones available.
 It can be applied in libraries, hospitals, laboratories, lecture rooms, meditation rooms amongst many others.

1.6 SIGNIFICANCE OF THE STUDY
This study will serve as a means of ensuring and maintaining a certain sound or noise level in wherever it is been applied. It will be useful in maintaining good health.

1.7 PROJECT ORGANISATION
The work is organized as follows: chapter one discuss the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.