The Technical Instructions on Noise (TA Lärm) contain protective and precautionary measures against harmful effects on the environment caused by noise. They shall be applied to installations subject to licensing and those not subject to licensing meeting the requirements of Part II of the Federal Immission Control Act.

These exceptions are made as the installations are assessed pursuant to other regulations or only with reference to TA Lärm due to their specificity (e.g. surface mines or the shooting with firearms).

The protection from harmful environmental effects is ensured as far as the total pollution, e.g. the sum of the noises from all installations to which TA Lärm is applied, does not exceed the immission guide values at the relevant place of immission. The relevant place of immission is that place in the neighbourhood of installations requiring protection where the highest total pollution is expected. As for built-up areas, this place can be situated in front of the windows of rooms requiring protection or, as for undeveloped areas, at the border of areas on which buildings with rooms requiring protection may be constructed. The immission guide values for both the rating level and the maximum level of single sound events are graduated according to the degree of protection required for each territorial category, which corresponds to the classification made in the Federal Land Utilisation Ordinance. The allocation complies with the designations in legally binding land-use plans or, if those are not available, with the degree of protection required for the actual use of the territory.

Section 6.1 of TA Lärm specifies the following immission guide values for places of immission outside buildings:

Single short-time peak values may not exceed the immission guide values by more than 30 dB(A) during the day and more than 20 dB(A) at night.

The term "immission guide value" implies that the values according to TA Lärm do not represent the limit of relevance (reasonableness) in any case. A number of factors, which do have an influence on the nuisance but whose weighing can differ significantly in a given case, is included in the assessment procedure. With its assessment of special cases, TA Lärm provides a basis of decision-making for such situations. A situation of that kind is given in the conflict situation at the border between commercially or industrially used areas and residential areas. The immission guide values can be raised to an appropriate intermediate value, if this is required due to the obligation to mutual consideration, but they may not exceed the values of mixed areas in category c).

Installation noises are assessed on the basis of the rating level and the maximum value of single sound events. The following factors must be determined: 

The rating level consists of the average sound level during the assessment period (the average value over the 16 hours from 6 am and 10 pm and the average value over the loudest hour between 10 pm and 6 am), of additions for discrete components, information incorporation, impulsive characteristics and daytimes with increased sensitivity and of meteorological corrections pursuant to DIN ISO 9613-2.

The rating level calculated in a sound immission prognosis is compared with the immission guide value when the immission control authorities check whether the obligation of protection is complied with in the case of installations subject to licensing; the same applies to the building control authorities in the context of installations not subject to licensing. A distinction is made between detailed prognoses with a high degree of accuracy, usually required for installations subject to licensing, and rough prognoses with a lower degree of accuracy for installations not subject to licensing. A prognosis is generally established according to the provisions in VDI guideline 2571 in connection with the method of calculation for sound propagation outdoors pursuant to DIN ISO 9613-2 as presented in section 4.2.3.

TA Lärm allows for exceptions in the context of establishing a sound immission prognosis and of adhering to the immission guide values, which may be exceeded under certain conditions, e.g. in an assessment of special cases.

Special provisions are also to be applied to rare events for which exceedances of the immission guide values during the operation of an installation are allowed on up to 10 days or nights of a calendar year (up to 14 in the case of several installations) due to the predictability of the particular situation. The allowance of exceedances is attached to strict assessment criteria (best available techniques, exhaustion of all operational and organizational noise reduction measures, reasonableness in a given case). Rating levels of 70 dB(A) at daytime and 55 dB(A) at nighttime are permitted for rare events in areas with a higher protection claim than industrial areas. Furthermore, sound level ranges are determined for this areas, specifying the short-time exceedances of the rating levels for single peak noises during rare events.

Another special provision is applied to traffic noises in the context of the operation of installations. Vehicle noises coming from the company site are added to the installation noises. Start-up and drive-off noises on public circulation areas are separately determined pursuant to the method of calculation in the 16th Federal Immission Control Ordinance. These noises shall be reduced through organizational measures near the company site (up to a distance of 500 m) if

-     they increase the rating level by at least 3 dB during the day or night,
-     they are not mixed with the other traffic and
-     the immission limit values of the 16th Federal Immission Control Ordinance are exceeded.

The principle saying that the total pollution must not exceed the immission guide values (also called acceptor reference), which is anchored in the Federal Immission Control Act and adopted by TA Lärm for installations within its scope, requires the examination whether an installation assimilates acoustically into the existing situation before it is authorized. An immission guide value percentage for the additional pollution on the basis of the existing pollution must be determined to this end. Noise allotment (see section 6.3.2) has proved to be an appropriate instrument for the determination of immission guide value percentages for larger commercial areas, where a number of installations from different operators has an impact on one place of immission.