The noise is a distortion element that pervades the environment around us causing a deterioration of environmental quality, is today one of the most aggressive atmospheric pollutants, noise pollution was considered one of the major environmental problems as not only cause a deterioration of the environment, but that is because of physical disorders (hearing loss) and psychological imbalances in people subjected to certain levels of noise. 
The noise acts through the body of the ear on the central and autonomous nervous systems. When the stimulus exceeds certain limits, there is deafness and pathological effects in both systems, both instantaneous and delayed. A much lower levels, the noise produced discomfort and hinders or prevents the attention, communication, concentration, relaxation and sleep. 
The recurrence of these situations can cause chronic stress and nervousness which in turn leads to psychophysical disorders, cardiovascular diseases and disorders of the immune system. 



Effects on people 

This is perhaps the most common effect of noise on people and the immediate cause of most complaints. 
The feeling of discomfort comes not only from interference with the ongoing activity or resting but of other sensations, less defined, but sometimes very intense, of being disturbed. People affected about restlessness, anxiety, restlessness, depression, helplessness, anxiety or anger. 

The level of discomfort varies not only according to the intensity of noise and other physical characteristics of it that are less objectivable (noise "squeaky," "strident", etc..) But also on factors such as fears associated with the source noise, or the degree of legitimacy that it confers on the affected. If the noise is intermittent also affect the maximum intensity of each episode and the number of these. 
During the day, often experience moderate discomfort from 50 decibels, and strong from the 55. In the evening period, in waking state, this decrease in 5 or 10 decibels. 
Interference with communication 
The sound level of a conversation in normal tone is one meter from the speaker, between 50 and 55 dBA. Speaking loudly may reach 75 or 80. On the other hand, the word is perfectly understandable that it is necessary to exceed their intensity by about 15 dBA background noise. 
Therefore, a noise above 35 decibels or 40 will cause difficulties in oral communication that can only be solved partly by raising the tone of voice. As of 65 decibels of noise, conversation becomes extremely difficult. 
Similar situations occur when the subject is trying to listen to other audio sources (TV, music, etc.).. Given the interference of a noise, it reacts by raising the source volume and creating greater noise without completely achieve the desired effect. 
Loss of attention, concentration and performance 
It is clear that when conducting a task requires the use of acoustic signals, background noise can mask these signals or interfere with their perception. Moreover, a sudden noise distractions that produce reduced yields in many types of jobs, especially those that require a certain level of concentration. 
In both cases, affect the performance of the task, getting errors and decreasing quality and quantity of the product itself. 
Some accidents, both labor movement may be due to this effect. 
In some cases, the consequences will be lasting, for example, children subjected to high noise levels at their school not only learn to read with greater difficulty, but also tend to achieve lower levels of proficiency in reading. 

Sleep Disorders 
The noise affects on sleep in three different ways that are, to a greater or lesser degree depending on individual characteristics, from 30 decibels: 
By difficulty or inability to sleep. 
Causing disruption of sleep, which, if repeated, can lead to insomnia. The probability of awakening depends not only on the intensity of the incident noisy but the difference between this and the previous level of noise stable. As of 45 dBA is the probability of arousing great. 
Decreasing the quality of sleep, it becomes less quiet and shortened its deepest phases, both of paradoxical sleep (dreams) and non-paradoxical. Increase blood pressure and heartbeat, there is vasoconstriction and changes in breathing. 
As a result, the person will not be well rested and will be unable to perform properly the next day their daily tasks. If the situation continues, the physical and psychological are severely affected. 
Often tries to avoid or at least alleviate these situations by the ingestion of tranquilizers, the use of hearing aids or earplugs to sleep by closing the windows. The first two practices were obviously unhealthy and not being able to carry natural units and additional discomfort. The third also lose quality to the dream to develop it in a poorly ventilated and / or with too high a temperature. 
Damage to the ear 
Permanent deafness is caused either by exposure to levels above 75 dBA, or by sounds of short duration of more than 110 dBA, or accumulating fatigue hearing without sufficient time to recover. Initially occurs at frequencies not conversational, so the subject is often not noted until it is too late, unless it is self-observation. May be accompanied by ringing in ear (tinnitus) and balance disorders (vertigo). 
Stress, manifestations and consequences 
Persons subjected to prolonged in situations like those described above (noises that have disturbed and frustrated their efforts to attention, concentration or communication or affecting your peace of mind, resting or sleeping) often develop some of the following syndromes: 
• Chronic Fatigue • Tendency to insomnia, thus worsening the situation. • Cardiovascular diseases: hypertension, changes in the chemical composition of blood, cardiac ischemia, and so on. Have been mentioned increases of up to 20% or 30% in the risk of heart attacks in people undergoing more than 65 decibels in daytime period. • disorders of the immune system responsible for the response to infections and tumors. • Psychophysical disorders such as anxiety, mania, depression, irritability, nausea, headaches, and neurosis or psychosis in people predisposed to it. • behavioral changes, particularly antisocial behavior such as hostility, intolerance, aggression, social isolation and reduce the natural tendency towards self-help.