We all  live among various sounds and noises. Some of them are useful signals, making it possible to communicate, correctly navigate the environment, and take part in the work process. Others interfere, annoy, and even harm our health.

Environmental noises (leaves, rain, rivers) have long been known to have a beneficial effect on the human body. Statistics show that people working in the forest, by the river, and at sea, have less instance of diseases of the nervous and cardiovascular systems than those dwelling in the city. It has been established that the rustling of leaves, singing of birds, babbling of brooks, and the sounds of rain all heal the nervous system. More than that, these sounds increase muscle work output.

The positive impact of harmonious music has been known for a long time. Just recall the lullabies that are widespread all over the world (gentle monotonous tunes), nervous stress relief by the sound of brooks, gentle sounds of sea waves or singing, etc.

The negative effects of sound are also known. One of the cruel punishments in the Middle Ages was forced listening to loud bell sounds when the condemned was dying in terrible agony from unbearable pain in the ears.

This defines the theoretical and practical importance of studying the nature of the impact of noise pollution on the human body. The main purpose of the research is to identify the threshold of adverse effects of noise and justification of hygienic standards for various population groups, different conditions, and places of residence (private, public buildings, industrial facilities, children’s and health care institutions, residential areas and vacation sites).

Of considerable theoretical interest are the study of pathogenesis and the mechanism of noise pollution effect, processes of the body adaptation, and consequences of distant noises of prolonged exposure. Studies are usually carried out in experimental conditions. It is difficult to study the nature of noise impact on a human being as the processes of interaction of physical and chemical factors of the environment with the body are also complex. Noise sensitivity of different age-sex and social groups of the population is also different.

A person’s response to noise depends on whether the central nervous system is dominated by excitation or inhibition.

Many of the sounds coming into the cortex of the great brain cause anxiety, fear, and early fatigue. This, in turn, can have an adverse effect on our health. The range of influence of noise pollution on a person is wide: from subjective sensation to objective pathological changes in the organ of hearing, central nervous, cardiovascular, endocrine, and digestive systems. Thus, noise affects vital organs and systems.

The following categories of effects of sensitive acoustic energy on humans can be highlighted:

  1. The effect on the auditory function of listening adaptation, auditory fatigue, temporary or permanent hearing loss.
  2. Violation of the ability to transmit and perceive the sounds of speech communication.
  3. Irritability, anxiety, sleep disturbance.
  4. Change of physiological reactions of a person to stress signals and signals which are not specific for noise influence.
  5. Mental and somatic health influence.
  6. Production activity, mental work influence.

City noise is perceived primarily subjectively. The first indicator of its unfavorable action is complaints about irritability, anxiety, and sleep disorders. The noise level and time factor are crucial in the appearance of complaints, but the degree of unpleasantness also depends on how much noise exceeds the usual level. A person’s attitude to the source of noise and the information in it play a significant role in causing the person to feel uncomfortable.

Thus, the subjective perception of noise depends on the physical structure of noise and psychophysiological features of a person. The response to noise in the population is not homogeneous. 30% of people are hypersensitive to noise, 60% are normally sensitive, and 10% are insensitive.

The degree of psychological and physiological perception of acoustic stress is influenced by the type of higher nervous activity, individual bio rhythmic profile, the type of sleep, physical activity level, the number of stressful situations during the day, nervous and physical stress level, as well as smoking and alcohol.

A survey of 1,500 residents of noisy streets showed that 59% complained about the noise of transport origin, 22% complained about industrial enterprises and 21% – about household noise. In 37.5% of respondents noise caused concern, 22% – irritation, and only 23% of respondents – did not complain about it. At the same time, those who suffered the most had suffered from damage to the nervous, cardiovascular, and digestive systems. Permanent residence in such conditions can cause stomach ulcer, gastritis for disorders of secretory and motor functions of the stomach and intestines.

In areas with a high level of noise, the majority of residents note a deterioration of health and visit a doctor more often. In a survey of 622 residents of quiet streets (LA equivalent = 60 dBA), 12% complained of vehicle noise, 76% of household noise, 8% of industrial noise, and 28% of aviation and railway noise.

The number of complaints from the public is directly related to the sound level in the mainland area. For instance, with an equivalent sound level of 75-80 dBA, more than 85% of complaints were registered, and with a 65-70 dBA – 64-70%. At 60-65 dBA sound levels, almost half of the surveyed complained about noise, while 55 dBA had a third of the population concerned, and only at 50 dBA noise levels had almost no complaints (5%). The last two levels are acceptable for residential areas. According to TheHomeDweller.com sleep disturbance usually occurs at sound levels greater than 35 dBA. The population’s response to transport noise is virtually independent of gender, age, and profession.

In today’s urban environment, a person’s hearing analyzer is forced to work with a lot of stress on the background of transport and residential noise which masks useful sound signals. Therefore, it is necessary to determine the possibilities of adaptation of the hearing organ, on the one hand, and the safe levels of noise, the action of which does not violate its functions – on the other.

Hearing thresholds characterize sensitivity. They are determined on pure tones in the frequency range from 63 to 8000 Hz by the method of tone audiometry in accordance with the “Noise. Methods of determination of human hearing loss” standard. The highest sensitivity of the ear to sounds is in the frequency range of 1000-4000 Hz. It is rapidly reduced with more distance in both directions from the area of greatest sensitivity. In the frequency range of 200-1000 Hz, the threshold sound force is 1000 times greater than in the frequency range of 1000-4000 Hz. The higher the tonality or noise, the greater its adverse effect on the hearing organ.

Sound waves, at the appropriate intensity and frequency, are specific stimuli for the ears. When noise levels are high enough, and the effects of noise are short, there is a decrease in hearing loss, resulting in a temporary increase in its threshold. Prolonged exposure to high-intensity sound can lead to permanent hearing loss which is usually characterized by a constant shift of sensitivity threshold.

Transport noise has a significant impact on the functional status of the hearing analyzer. For example, in a soundproof camera, even a relatively low sound level (65 dBA) at 2-hour exposure results in a hearing loss of more than 10 dB at low frequencies which corresponds to the low-frequency spectrum of transport noise. An 80 dBA noise level reduces hearing sensitivity by 1-25 dBA in a wide range of low, middle, and high frequencies which can be considered as hearing organ fatigue. In urban dwellings along highways, the population often complains of poor language perception due to the disguise of individual speech sounds by traffic noise. Noise has been found to interfere with speech intelligibility, especially if it exceeds 70 dBA. At the same time, a person does not understand 20 to 50% of words.

Noise through the conductive pathway of the sound analyzer affects different centers of the brain, changes the interaction processes of higher nervous activity, disrupts the balance of excitation and inhibition. At the same time, reflex reactions change and pathological phase conditions are detected. Prolonged noise effect activates the structures of the reticular formation, resulting in persistent disruption of various body systems.

To study the functionality of the central nervous system, a method of determining the latent time of the reflex reaction, chronoreflexometry, is widely used. Latent time in a quiet apartment (40 dBA) of a group of people in a quiet state on the light irritant is an average of 158 ms, on the sound – 153 ms; while resting in the neighborhood in noisy conditions, it increased by 30-50 ms. The shift criterion is the excess of reaction time by 10 ms. Thus, transport noise causes the processes of inhibition in the cortex of the great brain, adversely affects human behavior and reflexive activity.

An important indicator of the functional state of the central nervous system under the influence of various environmental factors is the ability to concentrate attention and mental activity. It is proved that disorders of the central nervous system under the influence of noise lead to a decrease in focus and efficiency, especially mental. At the level of noise of more than 60 dBA, the speed of information transfer, the amount of short-term memory, quantitative and qualitative indicators of mental performance decrease, the reaction to different life situations changes.

Noise Pollution Effects on the Cardiovascular System

Particular attention should be paid to the results of research into the effects of noise pollution on the cardiovascular system. Under its influence the pulse accelerates or slows down, the blood pressure rises or falls, and the ECG changes. In the laboratory environment, after 2 hours of intense transport noise (80-90 dBA), there is a marked decrease in heart rate, due to the lengthening of the heart cycle and a characteristic change in individual ECG values. Blood pressure fluctuations reach 20-30 mm in the mercury column. Changes in heart rate detected by variability in heart rate after 2 hours of exposure to flight noise and high sound level testing of aircraft engines (up to 90 dBA) were characterized as vagotonic (heart rate and breathing retardation, sweating, low BP).

Under the influence of aircraft noise, peripheral blood flow resistance increases (by 23%) and brain circulation changes. With the help of rheoencephalography, the increase of tone and decrease of filling the cerebral vessels with blood was detected. Based on this, we can assume the possible contribution of transport noise to the development of cardiovascular disease in large cities.

Noise pollution is one of the irritants at night: it disrupts sleep and rest. Under its influence, people fall asleep badly, often wake up. Sleep is superficial and intermittent. After such a sleep, the person does not feel rested. The study of sleep patterns in houses located on the streets with different levels of noise shows that sleep is severely disturbed at a sound level of 40 dBA, and if it is 50 dBA, the sleep period increases to 1 hour, the duration of deep sleep is reduced to 60%. Residents of quiet areas sleep normally if the noise level does not exceed 30-35 dBA. The average sleep period is 14-20 minutes, and the sleep depth is 82%.

Lack of normal rest after a working day leads to the fact that tiredness does not disappear but gradually becomes chronic, contributes to the development of hypertension and diseases of the central nervous system.

In some countries, there is a direct correlation between the growth of noise in cities and the increase in the number of people with nervous system diseases. French scientists believe that the increase in noise pollution levels over the past 4 years has contributed to an increase in the number of neurosis cases in Paris from 50 to 70%.

Urban noise plays a role in the pathogenesis of hypertension. These data were confirmed in the study of the morbidity of female housewives. There is a correlation between central nervous and cardiovascular lesions, noise levels, and duration of residence in noisy urban areas. Thus, the overall morbidity of the population is increasing after 10 years of living in conditions of constant exposure to 70 dBA noises and higher.

Author Bio: Roy Emerson is a technology enthusiast, a loving father of twins, a programmer in a custom software company. Editor in chief of TheHomeDweller blog, greedy reader and gardener.

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