The growth in human population has led to increased human activity, generating noise at different levels. Noise emitted from construction sites, vehicles, places of entertainment and other sources is a common phenomenon. Although noise pollution is not accorded considerable attention compared to water and air pollution, there is evidence suggesting that excessive noise is hazardous to both humans and wildlife.
Noise is defined by the Oxford Dictionary as unpleasant or disturbing loud sound. It is measured in a unit called decibel (dB). A decibel of 0 is a healthy hearing threshold. The following are decibels of some common sounds: rustling leaves (20 dB), conversational speech (60 dB), a passing diesel truck (85 dB), emergency vehicle siren (115dB) and firecrackers (makombola) generate 145 dB.
Excessive noise is harmful to both physical and psychological health of humans. The World Health Organisation Guidelines on Community Noise (1999) reported that the effects of noise include temporary and permanent hearing loss, sleep disturbances, disturbances in cardiovascular system (comprises heart and blood vessels) and impaired task performance.
Temporary hearing loss occurs due to shifting of hearing threshold at sound levels of 80 dB or greater. The extent of this problem in developing countries is hazy because of poor reporting system. However, it is estimated that 12.5 percent (approximately 5.2 million) of children aged 6 to 19 years in United States of America have this problem in one or both ears, according to Niskar et al. (2001). Sound that is greater than 150 dB can physically rupture the eardrum and cause permanent hearing loss.
Noise during the night disturbs sleep. This is common in residential areas which are close to factories or places of entertainment. It is important to understand that sleep is necessary for normal physiological functioning of the body. Sleep disturbance causes secondary effects which include increased fatigue and depressed mood.
Exposure to noise can also cause cardiovascular problems. These problems may arise from the effect of stress hormones (epinephrine and norepinephrine) which are produced as a response to noise. These hormones increase the rate at which the heart pumps blood and also reduce the lumen of blood vessels resulting into high blood pressure and heart problems.
Impaired task performance is another effect of noise pollution. This is evident in children who attend schools situated in noisy environment or adults who are exposed to noise at a workplace. The problem is manifested by decreased attention span, difficulties in problem solving and increased frequency of errors. This may affect class performance of the children and can also lead to inefficiency at the workplace.
There is also evidence that noise contributes to depletion of wildlife population. Excessive noise masks environmental cues for the presence of predators putting some animals at risk of death. Apart from that, noise affects reproduction in some animals. A study by Rasmussen et al. (2009) on the effect of construction noise on mice reported that noise decreased reproductive efficiency by decreasing live births and increasing the number of stillborn pups.
The effects of noise pollution cannot be ignored. As the countryâ€™s population continues to grow at 3.22 percent annually, according to National Statistical Office projections, it is necessary to put in place strategies to mitigate the effects of noise pollution. These strategies include good planning of urban areas and public awareness on adverse effects of noise.
Additionally, there is need for guidelines on prevention of noise originating from some activities. For instance, the countryâ€™s Environmental and Social Management Guidelines in the Road Sector (2007) stipulate measures that can help to prevent effects of noise during road development projects. Similar guidelines are necessary for other activities like mining which expose people to noise.Â
Some people may argue that noise perception is subjective because what is perceived as noise by one person may be good sound to another. For this reason, it is also essential to have regulations which prescribe permissible sound levels for different areas and activities. Enforcement of such regulations would help to ensure a tranquil environment for the wellbeing of both humans and wildlife.-The author is a lecturer in medical and surgical nursing at Kamuzu College of Nursing.