N
N
Nanogram
Natural gas
Mixture of hydrocarbons (See: Hydrocarbons), primarily methane (CH4). Forms in the interior of the earth during bitumization and carbonization of sludge, generally together with crude oil, above which it collects in a sort of lens over a salt dome (petroleum gas). It is non-toxic, cheaper and has twice the calorific value compared with illuminating gas. It is valuable as a domestic gas and also as a starting material for the chemical industry. Moreover, natural gas undergoes combustion without liberating soot or toxic gases, and is virtually sulfur-free.
Natural water
Water before treatment.
Neutralization
Mixing acid and lye, forming salt and water. Normal neutralization procedures include setting mortar, improvement of acidic soils with lime, and combating acid or lye damage with acids or lyes.
Nitrogen
Symbol: N. The main chemical element present in the air (approximately 78% by volume). It is part of the ammonium, nitrite, nitrate and amide compounds; it is an essential component of all proteins. It is obtained from the air using ammonia synthesis in large-scale technology operations. This primary nitrogen is used to produce a variety of substances that contain nitrogen. Primary areas of application are production of nitrogen fertilizers and plastics. Nitrogen is the most important nutrient (core nutrient) for plant development and plant yield in agricultural production.
Nitrogen oxides
Symbol: NOX. Gaseous combustion products of nitrogen. The nitrogen oxide NO is oxidized into nitrogen dioxide NO2 in the air. As harmful components of automobile exhaust emissions, nitrogen oxides are the prerequisites for the development of smog.
Noise
A mixture of several individual sounds with varying frequency ratios. Sound which bothers people, poses a nuisance or could be unhealthy. High noise levels can result in Noise-induced hearing loss due to destruction of the hearing nerves. Measurement and evaluation of noise is almost always carried out using the (A) noise level [decibel A = dB(A)], which takes into consideration the dependence of the ear's volume perception on the frequency as opposed to the previously used unit of phon.
Noise control
Active measures carried out to prevent noise or increase in existing noise levels (e.g. encapsulating machines, installing sound insulation, sound-reducing building components, city construction planning measures) and passive measures (e.g. ear protection). An important component of noise control is the Noise TI. However, this does not take traffic noise into consideration.
Noise exposure
Stress placed on the human organism by noise, e.g. by traffic noise, airplane noise, machine noise, etc. Excessive noise exposure is harmful to health (See: Noise-induced hearing loss).
Noise-induced hearing loss
Illness of the inner ear due to long-term exposure to noise levels above 85 dB(A). In extreme cases, the impact of noise can lead to deafness. The high sound levels leading to noise-induced hearing loss can come from places of work or from other non-work related noise such as night club music and traffic, etc. Noise-induced hearing loss caused by noise in the workplace is considered to be an occupational illness for which compensation is payable. Noise-induced hearing loss in areas of work is experiencing a downward trend due to increasing implementation of noise protection measures at places of work, the primary measure being the use of ear protection.
Noise measurement
The objective assessment of sound impact. See: Frequency spectrum.
Noise pollution
In Germany, 40% of the inhabitants feel that their lives are encroached upon by noise either intermittently or permanently. 70% percent of these people live on heavily trafficked streets or near airports. The affected people named the following causes of noise pollution to be the most intrusive in their lives: 60 to 70% street traffic noise, 20% airplane traffic noise, 10% industrial and business related noise and 12% miscellaneous other sources of noise.
Noise protection
Technical measures intended to protect against hearing impairment caused by noise exposure and used to prevent noise disturbance and noise pollution. See: Noise control.
Noise TI
See: TI