*2.1.1 Noise as a dangerous hazard*

*Noise and Environment*

suspected before.

origins, nausea.

population.

hazard [4].

during emergency.

**2. Literature review**

**2.1 Basics of acoustics**

finally can be classified as sound.

medium (e.g., air, water, wood, and metal).

able to process these impulses into meaningful sounds [5, 7].

The origin of the noun "noise" is found in Latin language from the term "nausea", which later via detours through French language was introduced as "noise" to the English language [3]. Both words have much more in common than

Substantially, there is no difference between sound and noise. But enlightening the differences more closely, sound refers to the sense of perception that usually occurs on voluntary basis and delights the listener as it is for example by listening to music. On the other hand, noise is defined as an unwanted sound that may cause displeasure, annoyance and pain or, referring back to its word

Investigations have shown that continuous noise exposure has an enormous damaging impact not only on hearing but also on the general health status of the

Although preventable, NIHL is one of the most widespread irreversible occupational diseases worldwide and thus was declared as a serious occupational

Several studies gave evidence that noise creates physical and psychological stress, commonly presented as reduced assessment, sleep disturbances, cardiovas-

The protection of health and safety from hazards at work should be our all interest. Therefore, our research is aimed at evaluating the impact of occupational noise on hearing, general security of health, quality of life and productivity of those working in stressful environments shown at the example of emergency service working personnel, who give constantly their best to protect and save our health

Noise can be described as rapid fluctuations in atmospheric pressure, which affects the human body as vibrations that are perceived by the human ear and

Sound propagates as a pressure wave and is able to travel through any elastic

Important units for measurements of noise attributes are hertz (Hz) and decibels (dB), and together with some basic knowledge of physics of waves, frequency, wavelength, amplitude, refraction, absorption and transmission, we are able to understand the behaviour of noise and can develop controls and preventions. When molecules start to move due to atmospheric pressure changes, the moving air molecules pass their energy on to neighbouring molecules, which results in the spread of their energy over and over until an increasingly larger volume is created. This principle can be compared to the ripples when a stone is thrown into water. These described pressure changes are detected by the eardrum, which in return vibrates as response. In return, the vibrations are further transferred to the middle ear, which is constructed of three tiny bones facing towards the fluid-filled inner ear. The inner ear contains tiny inner and outer hair cells, which convert the vibrations into electrical nerve impulses that then are sent to the brain. Finally, the brain is then

The perception of loudness of a sound is determined by two factors: sound pressure and frequency. The frequency (number of vibrations per second) is

cular dysfunction and mental health alteration [5, 6].

**4**

Every day, we are naturally exposed to loud, distracting and possibly hazardous noise. A common experience for everyone may be the example of continues ringing after a great concert or muffled sounds after working with loud tools (chainsaw, grass cutter, etc.).

Noise at prolonged exposure at 80 dB has unsafe effects to the auditory system but also to general health [5, 7, 8].

Studies proved that the risk for NIHL increases exponentially in noise-exposed population, who are exposed to noise level beyond 85 dB(A) for a prolonged time [9].

**Table 1** shows critically how noise is correlated with health that is shown in three different stages of noise levels in dB(A).

At the example of "Conversation", it can be nicely illustrated in what manner noise level has an impact on health.

A standard conversation is measured at approximately 50 dB(A), which at a prolonged exposure may lead to mental reactions (e.g., low concentration and annoyance); at 80 dB(A), for communication, the voice needs to be elevated remarkably that interferes with health shown in physical reactions (e.g., hypertonus); and at 90 dB(A), communication is not possible anymore, which in return in long term is unbearable and triggers pain threshold.
