DETERMINATION OF ACTUAL DISTANCES FOR INSTALLATION OF A 100 kVA NON-SOUNDPROOF POWER GENERATOR AT RESIDENTIAL AREAS

 

Etinamabasiyaka E. Ekott^*1, Donatus E. Bassey², Effiong O. Obisung²

^*1 Department of Physics, University of Uyo, Akwa Ibom State, Nigeria

² Department of Physics, University of Calabar, Cross River State, Nigeria

 

DOI: https://doi.org/10.29121/IJOEST.v4.i1.2020.60

 

ABSTRACT

Power generators should be professionally sited from the residential areas as noise from them demeans the superiority of our living. This work therefore presents determination of actual distances for installation of a 100 kVA non-soundproof power generator at residential areas. Measurements of noise levels with respect to distance, x from the generator were taken and linear regression method was used to analyse the data obtained. Environmental noise models were developed by using the relevant displayed parameters such as the maximum noise level of the generator, the attenuation coefficient and the coefficient of determination. The results obtained from the models developed, L(modelled) were compared with the results obtained from the physical measurements, L(measured) and there was insignificant difference between them. The results reveal that the distances, xc in metres in which its adverse effects covered in the residential areas were 0≤x_c≤67, while the distances, xs in metres at which it can be sited from the residential areas were 68≤x_s≤∞ . With the existence of x, the models developed in this work are recommended to be used as more reliable tools for environmental noise impact assessments.

 

 

1.      INTRODUCTION

 

Residential noise is described by World Health Organisation (WHO) as community noise or environmental noise or domestic noise [1]. The most important sources of community noise comprise air, rail and road traffic, neighbourhood, municipal work, and the construction plant, among others. Usually, noise from neighbourhood originates from building and installations associated with the food preparation business like cafeterias, restaurant, and discotheques; from recorded or live music; from playgrounds and car parks; from sporting events including motor sports; and from household animals for example barking dogs. The major sources of indoor noises include aeration systems, home appliances; office machines, and neighbours [2].

 

In the United States of America, the Environmental Protection Agency (EPA) identified noise as a hindrance since in the 1970s [3]. Then, the agency carried out a main study of noise and has continued to bring up to date its results. This means that the study of noise is a continuous phenomenon. As with all pollutants, noise demeans the value of our environment and is known to produce various negative effects both on structures and on humans. Noise has escalated to the point where it is currently the most important peril to the superiority of our existence. This increase in noise can be attributed to the ever-increasing number of people in the globe and the growing levels of economic affluence [4].

 

In this context, noise is defined as unpleasant sound [5]. However, noise can be described as the unwanted sound in the unwanted location at the unwanted occasion. The degree of “unwantedness” is usually a psychological issue since the effects of noise can range from temperate irritation to everlasting hearing loss and may be rated in a different way by special observers [2]. For this reason, it is often exigent to establish the benefits of dropping a specific noise. Noise does affect the inhabitants, humans, fauna, etc, in the natural environment. Some definite places influence noise contacts; so, it is invasive that it became difficult to run away from it. The public opinion polls almost constantly rank noise in the list of the most bothersome residential irritations. General noise sources are industry, neighborhoods and traffic. The industrial noise is one of the most annoying sources of noise complaints [6]. Elevated noise levels of adequate exposure time can result in short-term or permanent hearing damage. This is generally related to those working in industrial plants or operating machinery but can also take place at discotheques or near to aircraft on the ground if the duration is long enough. However, measurable hearing loss from many industrial sounds involves daily exposure for a number of years. On the other hand, community noise intrusions like traffic noise can obstruct speech communication, interfere with sleep and relaxation and disturb the capacity to perform difficult tasks [7].

 

In 1993, a study carried out by Cornell University indicated that children exposed to noise during classes experienced problem with various cognitive developmental delays in addition to words discrimination. Specifically, the writing learning mutilation called dysgraphic is usually related to stress on environment during classes [8] and [9]. Noise has been connected to vital cardiovascular health risks. In 1999, the WHO drew a conclusion that the existing evidence shown predicted a weak relationship between hypertension and long-term exposure to noise beyond 67 – 70 dBA [10]. More current studies have recommended that noise levels of 50 dB(A) at night may also increase the risks of myocardial infarction by constantly enhancing production of cortisol [11].

 

Fairly characteristic road levels of noise are adequate to reduce arterial blood flow and cause elevated blood pressures; in this situation it seems that a specific part of the populace is more vulnerable to vasoconstriction. This may occur because the noise bother leads to high adrenaline intensity to activate vasoconstriction (a reduction of the blood vessels) or separately through reactions from medical stress. Additional impacts of elevated levels of sound are high rate of vertigo fatigue, stomach ulcer and headaches [6]. The British Columbia Work’s Compensation Board (WCB) has set 85 dB as its highest tolerant level in the workplace. Above this limit hearing protection should be used. It states that the threshold of pain is attained at 120 dB and it classifies 140 dB as excessive hazard level. WHO safety noise levels are similar while EPA of Nigeria tends to have even a stricter standard of 70 dB as a maximum safe level of noise in workplace. They gave the safe level around home to be 50 – 55 dB [12].

 

Researches have shown that constant noise above 55 dBA causes serious annoyance and above 50 dBA moderate annoyance at home (WHO, 2007). In a non-workplace and for health and safety purposes, 55 dBA is set as a safety noise level for outside and 45 dBA inside. Hospital and school permissible levels of noise are 35 dBA [1]. In Britain, the current and advanced Ministry of Agriculture regulations established in January 2002 state that propane cannons can be no closer than 150 metres from residential areas, and 100 metres from other kinds of noise makers. These machines generate noise at levels between 115 and 130 dB. At 100 meters the noise generated is above 80 dB, and greater than 75 dB at 150 metres, which is much greater than specified safe levels for around the residence. In fact, beyond 80 dB is near to the level at which ear protection should be used [3]. Noise beyond harmless levels leads to numerous health impacts which include high blood pressure, annoyance, sleep loss, stress, hearing impairment, loss of productivity and the ability to concentrate, among others [2].

 

Hence, the study of noise is highly imperative so as to create awareness on the impacts of noise on the environment for the betterment of our society. In this research, the determination of actual distances for installation of a 100 kVA non-sound proof power generator at residential areas and the development of models for predicting and controlling environmental noise pollution from this kind of generator shall be carried out.

 

2.      MATERIALS AND METHODS

 

2.1. Physical Measurements

 

All the noise measurements were made using the sound level meter (SLM), modelWensnWS1361 with ½ inch electret condenser microphone. This model has both A and C weightings and 0.1dB resolution with fast/slow response. It has a measuring range 30 to 130 dBA or 35 to 130 dBC. Also, it is equipped with a built in calibration check (94.0 dB) and tripod moving. It has an accuracy of ± 1.5 dB. It has AC and DC outputs for frequency analyser level recorder, Fast Fourier Transform (FFT) analyser, graphic recorder and others. It also has electronic circuit and readout display and a weight of 308 g. The microphone senses the small air pressure variations related to sound and converts them into electrical forms.  These signals are then passed to the electronic circuitry of the instrument for processing. The readout displays the processed sound levels in dB. The sound level meter picks the sound pressure level at one instance in a certain location. Measurements were taken by adjusting the sound level meter to A-weighting network in all the sampling locations. The sound level meter was calibrated. The manufacturer’s manual gave the calibration procedure. During the noise level measurements, the microphone of the sound level meter was positioned at a distance of above 5 m from the generator at a height of 1.2 m above the ground and windshield was always used for accuracy. Slow response was used for comparatively stable noise measurement. For instance, workplace noise level measurements were taken on slow response. Here, the response rate is the time period over which the instrument averages the sound level before displaying it on the readout. Measurement of workplace sound pressure was made in the uninterrupted noise field in the workplace, with the microphone located at the position normally occupied by the ear exposed to the highest value of exposure [14].

 

2.2. Noise Level with Distance Measurements

 

In this case, a workshop with a 100 kVA non-soundproof power generator was identified Measurements of noise levels from it as they vary with distance were taken. All noise level measurements were carried out using the sound level meter stated earlier, while distance measurements were made using a measuring tape. Lastly, L_eqs for them were evaluated and the results are presented in section 3.

2.3. Calculating the Equivalent Continuous Noise Level (L_Aeq)

 

The L_Aeq is the steady noise level over a certain period of time that generates very similar quantity of A-weighted energy as the varying level over identical period. It is presented in equations (1-2) and it is measured in dBA.

 

                                                                                                          1                                                                      

                                                                                                      2

 

Where,

T          = time period over which L_Aeq is determined

P(t)      = the instantaneous A-weighted sound pressure

P_o        = the reference sound pressures (20 μPa)

L_i            = noise level in the ith sample

 

Formula used for calculating the equivalent continuous noise level L_eq of a noise source, N at a particular distance, x is presented in equation (3) [7].

 

                                                                               3

 

The noise level of a noise source, L_N is presented in equation (4) [15]; [7] and [16]

 

                                                                                            4

 

Where,

T          =Time period over which L_eq is determined

ΔT_N     =Time period over which noise level of a noise source is measured

ΔT_B      =Time period over which background noise level is measured

L_N        =Noise level of a noise source in dBA

L_B        =Background noise level in dBA

L_TOTAL =Total noise level in dBA.

and,

T          =  5 minutes, ΔT_N       = 2 minutes, ΔT_B         = 3 minutes

 

2.4. Noise Modelling

 

The data obtained were analysed and the linear regression method was used. Hence, linear fitting models were developed for it by using the relevant displayed parameters such as the maximum noise level of the generator, the attenuation coefficient and the coefficient of determination. Finally, a general model for evaluating, controlling and predicting environmental noise pollution from a source of this type was developed. The results are presented in sections 3.

 

 

3.      RESULTS AND DISCUSSIONS

 

3.1. Analysis of Noise Levels and Distance Measurements from A 100 kVA Non-Soundproof Power Generator

 

The results of the survey (Table 1 and Fig.1) show that when the 100 kVA non-sound proof power generator is put to use, the total noise level (noise level with generator) at a distance of 65 metres is approximately equal to 55.4 dBA instead of a safety noise level of 55 dBA. This can cause serious annoyance. Moderate annoyance can occur between 70 – 75 metres if the generator is operated at night. Considering the L_eq the power generator adversely affects the residents up to distances of 55 metres with the L_eq approximate value of 55.34 dBA. Here, moderate annoyance may occur between distances of 60 – 65 metres if the generator is switched on at night. The levels of the background noise (from x = 5 metres to x = 100 metres) show that the area is conducive in the absence of the power generator. At a distance of 65 m from the generator, the noise level of the generator is 55.34 dBA instead of the WHO tolerant level of 55 dBA for residential areas.

 

Table 1: Noise levels and distance measurements from a 100 kVA non-soundproof power generator

 

Figure 1: A 100 kVA non-soundproof power generator noise levels against distance

 

Figure 2: The characteristics of the 100 kVA non-sound proof power generator measured noise level

 

Figure 3: The characteristics of the 100 kVA non-sound proof power generator modelled noise level

Figure 4: Comparism of modelled noise levels, L_{G100(modelled)} and measured noise levels,    L_{G100(measured)} of a 100 kVA non-sound proof power generator

 

3.2. Model Development for Noise Levels and Distance Measurements of A 100 kVA Non-Sound Proof Power Generator

 

The results of the analysis of a 100 kVA power generator noise levels, L_G100 show that the noise levels of the power generator and distance, x are strongly correlated with the coefficient of determination, R²=0.99301. Hence, a linear fitting model in dBA for the generator noise levels is presented in equation (5).

 

                                                                                                      5

 

Considering the error term,  equation (5) becomes

 

                                                                                         6

 

In equation (5), if, the noise level of the power generator at source is:

 

                                                                                                                   7

 

The intercept or the maximum noise level (87.27031 dBA) has a standard error of 0.55303 dBA. The model has a slope of –0.47992 dBAm^-1 with a standard error of 0.00923 dBAm^-1.  Comparing the measured noise levels, L_{G100(measured)} with its predicted noise levels of the power generator, L_{G100(modelled)} (Table 2 and Figs. 2-4) show that there is no significant difference between them. This simply shows that they are strongly correlated. Hence, equation (5) or (6) is recommended to be used as a model for evaluating, predicting and controlling environmental noise pollution from a noise source of this kind. The following conditions satisfy the model presented as equation (5):

 

; at ,           

                                   

; at ,

                                               

Condition (II) implies that the adverse effects of the noise from the 100 kVA non-sound proof power generator cover distances from 0 m (point of its installation) to 67 m. This is because at a distance of 67 m from the power generator, its noise level is 55.11567 dBA instead of the WHO tolerant level of 55 dBA for residential areas. The distance at which the adverse effects covered is denoted by x_c in metres. Condition (II) means that the 100 kVA non-sound proof power generator should be installed or sited from the residential area at a distance of 68 m and above. This is because at the distance of 68 m, the noise level of the power generator is 54.63575 dBA, which is less than the WHO recommended level of 55 dBA. Here, x_s is the distance it can be sited in metres (m).

 

Table 2: Comparison of modelled noise levels, L_{G100(modelled)} and measured noise levels, L_{G100(measured)} of a 100 kVA non-sound proof power generator

 

3.3. Development of A General Model for Evaluating, Predicting and Controlling Environmental Noise Pollution from A 100 kVA Non-Soundproof Power Generator

 

Generally, it is observed that all the models developed in this work are of the forms in equation (8) and equation (9).

 

                                                                                                                                 8

 

                                                                                                                                              9

 

 

Where,

 is the slope representing the attenuation coefficient of the noise from the 100 kVA non-sound proof power generator and it is measured in dBAm^-1.  is the intercept or the maximum noise level signifying the noise level at source (i.e at x = 0) in dBA. x is the distance in metres (m) and  is the coefficient of determination. Substituting equation (8) into equation (3), gives equation (10).

 

                                                                       10

 

Equation (10) shows that when  and  for the 100 kVA non-soundproof power generator are known, L_eq of the noise source can be determined at any distance, x with the consideration of the background noise level, L_{B at} that point. Hence, with the introduction of the distance of measurement, x equation (10) can be used as a more scientific and reliable general model for evaluating, predicting and controlling environmental noise pollution from the 100 kVA non-soundproof power generator. Therefore, this model can be applied in environmental noise impact assessment. L_eq is the equivalent continuous noise level. It is measured in dBA.

 

4.      CONCLUSIONS AND RECOMMENDATIONS

 

It is concluded from the findings that the maximum noise level the 100 kVA non-soundproof power generator is (87.27±0.55) dBA. The results indicate that the distances, x_c in metres at which the adverse effects of the generator covered in the residential areas are are , while the corresponding distances, x_s in metres in which it can be installed from the residential areas are . The results of the findings show that the models developed in this work can be used in evaluating and predicting the exact distance at which adverse effects of noise from this generator can cover and in controlling environmental noise pollution from a generator of this kind. The models require less cost, less manpower and less time than physical measurements. They can be used by the manufacturer of the generator to reduce its maximum noise level. Hence, the models are recommended to be used as reliable tools for environmental noise impact assessment as the results show insignificant difference between the measured noise levels, L_(measured) and the modeled noise levels, L_(modelled).

 

ACKNOWLEDGEMENTS

 

We hereby thank all those who contributed in one way or the other for the success of this work.

 

REFERENCES

 

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