One of the most undesirable side effects of an improperly planned city and poor building construction is environmental pollution and the degradation of quality of life. Noise pollution is an important significant environmental problem in many rapidly growing cities (Bjork et al., 2006; Gangwar, Joshi, & Swami, 2006; Kisku et al., 2006). Frequent exposure to high levels of noise has the potential to cause severe stress on the auditory and nervous systems (Stansfeld, Haines, Berry, & Burr, 2009). Extended exposure to excessive sound has been proved to cause physical and psychological damage (World Health Organization [WHO], 2011). Noise adds to mental stress due to its annoyance and disturbance implications, and hence affects the general well-being of those exposed to it (Agarwal & Swami, 2011; Finegold, Harris, & von Gierke, 1994; Singh & Davar, 2004). The primary urban sources of noise are industrial, traffic, and community noise--of which traffic noise is the most important. In traffic noise, vehicles contribute about 70% of noise. Vehicle noise is created by the engine and the exhaust system of vehicles, aerodynamic friction, interaction between the vehicle and road system, and by the interaction among vehicles and indiscriminate use of vehicle horns (Bjork et al., 2006; Chauhan, Pawar, Kumar, Kumar, & Kumar, 2010; Pathak, Tripathi, & Mishra, 2008; Rao & Rao, 1991).
In physics, sound is a mechanical energy of a vibrating object transmitted by pressure waves through a medium such as air or water that is capable of being detected by the human (or animal) hearing organs. According to the World Health Organization (WHO), environmental noise is an unwanted or harmful sound created by human activities (Berglund, Lindvall, & Schwela, 1999; WHO, 2011).
Unlike chemical pollution, noise energy does not accumulate in the body or in the environment, but it can have both short- and long-term adverse effects on people. Perceptions of sound and noise are highly subjective: one person's music is another's headache. The two terms are often used interchangeably, although few would call the sound that emanates from a highway anything but noise. Sound (and noise) is actually a process that consists of three components: the sound source, sound path, and sound receiver.
Meanwhile, sound pressure level is a measure of the air vibrations that make up sound. The human ear can detect a wide range of sound pressure levels, expressed in Pascals (Pa) from 20 pPa to 200 Pa, that are measured on a logarithmic scale with units of decibels (dB) to indicate the loudness of a sound. Sound pressure level changes continuously with time or distance, and within certain ranges.
Elevated levels of noise can be a serious threat to public health. Some of the adverse effects of noise pollution are psychological effects, speech interference, sleep disturbance, and poor work performance. Noise is a biological stressor. Among the health risks posed by noise pollution are high blood pressure, coronary heart disease, ulcer, colitis, and migraine headache. It has been demonstrated that there is a relationship between high noise level exposure and health problems (Babisch, 2011; Babisch, Gallacher, Elwood, & Ising, 1988; Concha-Barrientos, Campbell-Lendrum, & Steenland, 2004). Exposure to loud noise increases an arousal response in the body. Adrenaline is released in the blood; heart rate, blood pressure, and respiration increase; gastrointestinal mobility is restricted; blood vessels contract; and muscles are stretched. Even though noise has no relationship with danger, the body automatically responds to noise as a warning signal (Babisch, 2002; den Boer & Schroten, 2007; van Kempen et al., 2012).
Even relatively low levels of noise can adversely affect human health and quality of life (Allaouchiche, Duflo, Debon, Bergeret, & Chassard, 2002; Berglund et al., 1999; Bharanthan et al., 2007). Noise is a psychosocial stressor that activates the sympathetic and endocrine systems. Acute effects occur at high sound levels in occupational settings, and also at lower environmental noise levels when certain activities such as concentration, relaxation, or sleep are disturbed.
The aim of this study is to measure noise level distributions in the metropolis of Lagos, Nigeria, and compare the obtained values with international standard limits, with the purpose of evaluating the possible adverse health effects of noise levels on the generality of the residents.
Materials and Methods
A digital sound meter (DSM 325) was used to measure sound levels in the selected study areas. DSM 325 is a handheld meter for a wide range of applications where accurate sound level measurements are required. The DSM 325 has a measurement range of 32-130 dB over three ranges (32-80 dB, 50-100 dB, and 80-130 dB) with a resolution of 0.1 dB and an accuracy of [+ or -] 1.5 dB.
Lagos has a population of approximately 17.5 million people and is the economic nerve center of Nigeria. We selected 32 locations for data collection (Table 1). Factors considered for the selected locations included commercial activities, vehicular traffic, closeness to the motor parks, and markets.
The DSM 325 was placed on a tripod stand at...