Section 1: Introduction to Noise
What is the Noise?
We are consistently exposed to various forms of noise in our day to day lives. There is a very fine line of difference between sound and noise. Noise is any unwanted sound that is unbearable or can be deafening. The human auditory system can identify the sound waves of frequency from 20 Hz to 20KHz. The human ear can detect sounds that come in between 0 dB i.e., hearing threshold and around 140 dB i.e., pain threshold. The harmful effects of noise depend on the duration, frequency, and intensity. A high and low pitch noise is much more damaging than middle frequencies.
Noise pollution is as harmful as other forms of pollution. It is loud and unwanted, unpleasant, or excessive sound, prevalent in our environment, that can have harmful effects on human organs. It is becoming omnipresent these days.
What Are The Types Of Noise We Encounter In Our Daily Lives?
Environmental noise can be of various types :
- Workplace Noise: It includes noise in an industrial area, commercial areas, or construction sites.
- Transportation Noise: It includes noise due to rail traffic, air traffic, road transport, sonic booms, etc.
- Household Noise: Any other miscellaneous noise which can be a result of household chores, TV, blender, grinder, washing machines, pressure cookers, etc.
Noise And Its Related Health Impacts on Human Organs
The health-related effects of noise are not at all new. There are a good amount of scientific insights that exposure to noise can lead to adverse health effects.
The Committee on Noise and Health, which is an international organization of the Health Council of the Netherlands (HCN) had assessed the health impacts of environmental and occupational noise in 1994. Other than hearing losses, noise can adversely affect various human organs such as heart, brain, etc. Also, there are multiple effects of noise such as sleep disturbances, effects on performance and behavior of individuals, stress-related impacts, loss of concentration, annoyance, hypertension, etc. as described by the Health Council of Netherlands in 1994.
The human ear is not equally sensitive to all sounds of different frequencies. Therefore the sound pressure level (L) is ‘A-weighted,’ and expressed in dB.
Important noise metrics are:
LAeq,T: The equivalent sound level over a period of time: LAeq,T = 10 lg (1/T T∫10L(t)/10 ) dt.
Ldn: The day-night level. This metric is the equivalent sound level over 24 hours, with the sound levels during nighttime (22 – 7 h) increased by 10 dB(A).
Lden: The day-evening-night level. This metric is the equivalent sound level over 24 hours, with the sound levels increased by 5 dB(A) and 10 dB(A) during the evening (19 – 23 h) and nighttime (23 – 7 h), respectively.
SEL: Sound Exposure Level. A metric used to describe single noise events. This metric can be defined as the equivalent sound level during the event, normalized to a period of 1 second.
In this article, we will describe various impacts of noise on different human organs and human health.
Section 2: Description Of Health Effects Due To Noise
Various adverse effects on human organs have been described by the Health Council of the Netherlands, Committee due to noise and by Passchier-Vermeer along with Passchier in 2000, and will be briefly explained here.
2.1 Noise-induced Auditory Effects
Noise-induced hearing impairment
According to WHO, a 10% population of the world’s population is exposed to such sound pressure levels, which could potentially be responsible for noise-induced hearing impairment. In half of such a population, auditory damage can be proportional to intense noise.  When noise exposure changes the hearing patterns in a human ear, it is called sociocusis. For example, according to a study, a noise exposure that ranged from 8 hours a day and five days in a week, which had a sound pressure level of 102 dB, lead to a median hearing impairment/ loss at a frequency near to 4000 Hz.
The main pathological pathway of this loss is due to the loss of cochlear auditory sensory cells. Since these hair cells are not able to regenerate in the mammals, therefore, no remission occurs. It is a public health problem. According to the Global Burden of Disease, it estimates that 1•3 billion people are encountered by hearing impairment. Also, researchers rate this hearing loss as the 13th most prevalent to the global years lived with disability (YLD)
Occupational Noise-induced hearing loss
In many developed countries, there are regulations about the exposure limits of noise, including guidelines for protective equipment, audiometric testing, noise assessments, etc., which are done to protect both employees and the public from unwanted noise exposure.
The exact limit of noise exposure in industrial areas that carries the risk of hearing loss is still a concern of debate internationally. The US Occupational Safety and Health Administration sets the permissible limit of exposure at LAeq8h 90 dB.
In the USA, hearing loss due to noise is one of the most prevalent occupational diseases, and about 22 million workers in the US are exposed to such harmful noise levels daily at work. Additionally, an estimated of around US$242 million is spent on compensation for hearing impairment disability in the US annually.
Diagnosis of noise-induced hearing damage
The main diagnostic advancement for hearing impairment is the development of otoacoustic emission testing. These are a liberation of acoustic energy, which can be recorded in the ear canal, and are released from the cochlea. According to a longitudinal study, it suggested that these emissions can be used to diagnose for noise-induced hearing loss.
Therapeutic strategies and certain scientific advancements
Individual researches state that stem cells can be used to recover the cochlear damaged sensory circuits at an early stage and may lead to potential therapeutic ailment.
Investigations suggested that oxidative stress may contribute to cell damage in the cochlea, and certain antioxidant compounds like glutathione may improve noise-induced hearing loss in animals and might also prevent noise-induced hearing damage.
D-methionine, which is an oral otoprotective drug can prevent noise-induced hearing damage in animals even if first given within early hours as soon as after a noise exposure; but still, further clinical trials may approve the efficiency of this drug in humans.
2.2 Noise-Induced Non-Auditory Health Effects on Humans
2.2.1 Cardiovascular Related Health Effects of Noise
Chronic noise exposure can lead to an imbalance in the homeostasis of an organism, which can affect the metabolism and cardiovascular system, It can increase the risk factors of cardiovascular disease like BP, blood lipid profiles, and blood glucose levels. These changes can increase the risk of diseases such as arteriosclerosis, hypertension, myocardial infarction, and stroke.
Many studies reported that exposure to loud noise could increase blood pressure.
The impacts of occupational noise on the cardiovascular system were studied in the workers of lock manufacturing factories, who were exposed to noise levels, which were exceeding 80 dB. It was noted that there was a significant increase in the diastolic blood pressure(DBP), systolic blood pressure (SBP), pulse pressure, mean arterial pressure, and heart rate in the assessed workers. The recorded parameters were compared with the people who had never lived or were exposed to a noisy environment.
The relative risk of developing hypertension in adults who are living in areas besides road or aircraft noise increases at equivalent sound levels for over 24 hours at a level above 70 dB, which are measured at the facade outside the dwelling (HCN, 1994).
Also, studies were conducted on children who were exposed to aircraft noise in the Munich airport and overnight resting concentration of epinephrine along with norepinephrine were found to be significantly higher, in comparison to control groups
2.2.2 Sleep Disturbances Caused Due to Noise
Sleep disturbance is one of the most harmful non-auditory impacts of environmental noise exposure because sleep of a reasonable length is required for alertness and performance in our day to day lives, quality of life, and health.
Maximum noise pressure levels, which can be as low as L Amax33 dB, may induce physiological reactions during sleep like autonomic, motor, and cortical arousals as in body movements, tachycardia, awakenings, etc. According to WHO, average nocturnal noise limits less than LAeq outside 55 dB is an interim goal, and 40 dB a long-term goal to prevent noise-induced health effects.
2.2.3 Gastric Effects of Noise
A lot of gastric market responses also occur due to unwanted and loud noise exposure. According to a study done by Smith and Laird, there was a decrease of 37% in the stomach during 80 dB noise, which was a significant change. But these are not similar to ulcers, as studies still have not predicted that to be true.
2.2.4 Effect of High Noise Levels on Brain
Specific, measurable changes in the potentials of the brain appeared in noise-exposed workers. In a study on Italian weavers, Bell found out that their responses occurred to be hyperactive. In particular, EEG, a diffuse desynchronization, was observed, which usually happens in psychoneurosis in personality disturbance.
2.2.5 Cognitive Performance
According to WHO, around 45000 disability-adjusted life- years are every year lost in high-income western countries in Europe in children aged 7–19 years, due to environmental noise exposure.
Specific noise effects on children’s cognition may include noise annoyance, impaired attention, communication difficulties, increased arousal, frustration, learned helplessness, and inevitable consequences of sleep disturbance, which may impact performance.
More than 20 studies have suggested that environmental noise exposure has a whole lot of adverse effects on children’s cognition and their learning outcomes and their day to day performance. Also, it is shown that children who are exposed to road traffic, chronic aircraft, or rail noise at school have less reading ability, less memory, and less performance on standardized national tests. The results were compared with other children who are not exposed to such noise at school.
According to RAANCH study which was conducted on 2844 students aged between 9–10 years and was attending 89 schools around Heathrow in London, the UK, Schiphol in Amsterdam, the Netherlands, and Madrid-Barajas in Spain airports had shown a linear exposure and effect relationship between airplane noise exposure at school and child’s reading ability and memory recognition after adjusting various social and economic factors. An increase of LAeq 5 dB in aircraft noise exposure was related to a delay of 2 months in the reading age of children in the UK and a month delay in those residing in the Netherlands.
Also, WHO has laid down specific Community Noise Guidelines, which suggest that during teaching sessions, the background sound pressure levels should not at all exceed LAeq 35 dB.
Annoyance is one of the most prevalent community responses during a population exposed to environmental noise.
Annoyance is a feeling of displeasure, resentment, dissatisfaction, discomfort, or offense when noise interferes with thoughts, feelings, or actual activities which an individual is going through.
Noise annoyance may result from noise interfering with daily activities, feelings, thoughts, sleep, or rest, and could be amid negative responses, like anger, exhaustion, displeasure, and by stress-related symptoms.
Additionally, investigators have gathered various evidence-based data for community annoyance in residents exposed to noise in their home supported along with exposure-response relationships were derived (e.g., for wind turbines). However, still, it is not possible to predict individual noise annoyance because a large variety of endogenous and exogenous characteristics are prevalent that affect annoyance.
2.2.7 Speech Interference
Noise exposure, which increases the ambient background level, may cause interference of conversation either by disturbance of the speaker (the speaker will need to speak louder) or by masking speech leading to a reduced comfort of the listener and a decrease in sentences perceived.
This report provides a summary of varied sorts of environmental noise on the health of a private in the living environment.
Hearing damage caused by various sorts of occupational or household noise exposure is very prevalent around the world. It constitutes an immediate public health threat that needs preventive and therapeutic strategies to beat this issue. Through this report, we emphasized both the auditory and non-auditory related impacts of environmental noise on various human organs.
These factors stress the necessity to manage and reduce environmental noise exposure (ideally at the source) and to enforce exposure limits to mitigate adverse health consequences of chronic exposure to environmental noise.
Educational campaigns for youngsters and adults can promote both avoiding the noise and reducing it, and thus, mitigate all the negative health consequences.
Lower amounts of annoyance will eventually reward efforts to scale back noise pollution exposure, improved learning environments for youngsters, improved sleep, lower prevalence of various kinds of disorders, and a happy yet healthy life of individuals across all age groups.
- Basner, M., Babisch, W., Davis, A., Brink, M., Clark, C., Janssen, S., & Stansfeld, S. (2014). Auditory and non-auditory effects of noise on health. The lancet, 383(9925), 1325-1332.
- De Kluizenaar, Y., Passchier-Vermeer, W., & Miedema, H. (2001). Adverse effects of noise exposure to health. report prepared for the EC Project UNITE by TNO PG, Leiden, NL.
- Aluko, E. O., & Nna, V. U. (2015). Impact of Noise Pollution on Human Cardiovascular System. International Journal of Tropical Disease & Health, 6(2), 35-43.
- Bugliarello, G., Alexandre, A., & Barnes, J. (2014). The impact of noise pollution: a socio-technological introduction. Elsevier.
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- How Does Noise Pollution Affect Our Ears & Ways To Protect Our Ears?
- Noise-Induced Hearing Loss: Causes, Signs, Symptoms, Treatment, Pathophysiology, Prevention