Traffic Noise 1993

Introduction

In Berlin there are currently 1.28 million motor vehicles registered. Not only does their use lead to enormous noise pollution in the road areas but, also both day and night, permanently detract from the living and occupational quality of the buildings and land located near the main network road. The effects are particularly grave in streets with traffic volumes exceeding 50,000 motor vehicles per 24 hour period. (e.g. Sachsendamm, Schöneberger Ufer, Frankfurter Allee, Gruner Strasse and See Strasse). Although these streets comprise only 1.7 % of the total length of the approx. 1,200 km long primary road network (main network), they carry approx. 19 % of all vehicle traffic.

Technical construction modifications to motor vehicles have resulted in significant reductions in the level of motor noise in the past years. In 1983, the EC’s permissible noise emission level for motor vehicles lay at about 10 dB above today’s limit, i.e. 10 vehicles of the current models are – from the standpoint of motor noise – not louder than one which was registered in 1983.

Despite that Berlin’s streets have not become any quieter. The reason for this is the enormous increase in motor vehicle traffic and the fact that virtually no progress has been made in reducing the amount of noise from tires and road surfaces. The introduction of “30 km / hour” zones for 70 % of all roads has resulted in a reduction of traffic noise but, noise in the main traffic arteries has increased. Noticeable reductions can also be found for the sections of the tram network where the track beds have been renewed.

As a whole it is the noise from the primary road network – compared with other sources such as rail and air traffic, industry and small business as well as sports and leisure noise which because of both its extent and the number of affected persons – presents the most problematic pollution.

Noise is to be understood as every kind of sound which is undesired, disturbs, or irritates, and which detracts from physical, psychological, or social well-being.

Depending on the duration and intensity, noise can lead to a number of problems. Some of these are among others:

• reduction of the ability to concentrate,
• communications disturbances,
• disturbances to sleep and recreation,
• negative influences on vegetative nervous system (high blood pressure, cardio-vascular-complaints, disturbances in digestive organs),
• obstructions resp. damage to hearing,
• increased risk of cardio-vascular illnesses.

Fig. 1: Volume of Certain Noise Sources and their Possible Effects

Noise is subjectively valued sound and is therefore dependent on the respective attitude toward the given sound, the condition at the moment, the activity engaged in, and the level of current need for quiet, etc..

It is difficult to provide a scale for the degree of annoyance caused by a sound. Along with the previously mentioned subjective parameters, the following also play a role:

• information content of the sound,
• time of occurrence,
• temporal quality,
• frequency,
• impulse and tonal content,
• transmission route,
• specific source.

Described physically, sound is caused by vibrating bodies, i.e. by pressure variations within elastic medium (gases, liquids, solid bodies). The pressure variations can be caused by impact, rubbing or streaming gases (the principle of all musical instruments). The pressure variations caused disperse through the ambient medium air at high speed (330 m/s) and can be perceived by the ear if they reach sufficient intensity – if the vibrations per second (measured in hertz [Hz]) are greater than 16 and less than 20,000.

The pressure variations within the range of perception by the human ear (vibration amplitude or sound volume) lies between 20 µPa (audio threshold) and 200,000,000 µPa (pain threshold). Micropascal (µPa) is the measuring unit for this pressure.

To avoid having to deal with such huge numbers, a logarithmic measure was introduced, the so-called decibel (dB) – scale. In this case, 20 µPa equals the audio threshold, 0 dB and 200,000,000 µPa (pain threshold) 140 dB.

The decibel scale, which describes the ”sound pressure level”, is therefore not an absolute unit of measurement, such as i.e. the gram or the meter. Rather it only specifies the relationship to the audio threshold, i.e. it tells how much a sound exceeds the audio threshold.

As a rule, sounds consist of a mixture of high, medium and low frequency segments. The human ear perceives these frequency segments with various degrees of sensitivity. In order to reflect these properties of the ear, measuring devices are equipped with acoustic filters. The acoustic filter ”A” shows the best correspondence between ear and measuring device for the usual environmental sounds. The corrected sound volume is therefore given in ”dB(A)”.

The sounds found in our environment, e.g. also traffic noise, are rarely uniform. Rather they exhibit short-term fluctuation as well as in the course of the day and week (c.f. Map Traffic Volume 07.01).

Therefore, to assess and compare sounds, it is practical to use a ”single value”, which is an average of the sound volume level occurrence.

In other words: a sound fluctuating within a particular time segment is replaced by a constant sound with constant volume level and equivalent energy. ”Mean volume” is also called the (energy-) ”equivalent constant sound volume”. Thus, the mean volume is not to be understood as an arithmetic average but as corresponding to a physically equivalent energy average. This procedure allows the peak noise to be given special consideration.

The logarithmic laws are applied to calculations with sound volume. Thus the e.g. die doubling of the number of similarly loud sound sources (motor vehicles) increases the sound volume by 3 dB (equals 10 · log 2); a trebling by 5 dB (equals 10 · log 3), ten times by 10 dB (10 · log 10). A sound with a 10 dB(A) higher level is felt as if twice as loud.

In the same way, a quadrupling of the exposure time for sounds within a certain assessment period (day resp. night) has a similar effect. That means a prolongation of the exposure period, e.g. from 10 to 20 minutes or from 2 to 4 hours, increases the mean volume by 3 dB. A shortening of the exposure period of a sound from 600 to 60 minutes would correspond to a volume reduction of 10 dB.

In comparison to limits or standards, the so-called ”assessment level” is usually given. This is distinguished from the mean, resp. equivalent constant volume in that particular increases or decreases which take into account the various noise perception levels. In the case of traffic noise, increased perception levels for brake and acceleration sounds especially near traffic signals taken into account by means of an increase.

The empirically demonstrated reduced perception level for rail traffic noise is taken into account by a decrease, the so-called rail bonus.

The statutory regulations for limiting road traffic noise pollutions on existing streets remain currently unsatisfactory.

The Federal Pollution Control Law and the Traffic Noise Control Regulation (16 BImSchV) as well as the Traffic Routes and Sound Protection Measures Regulation (24 BImSchV) are only valid for the construction or substantial modification of road or rail routes.

Existing traffic noise situations are not subject to these regulations.

According to 16 BImSchV the following pollution limits apply:

Tab. 1: Limits of the 16 BImSchV (Traffic Noise Control Regulation)

For streets and city expressways maintained by the federal government, there are noise abatement measures available pursuant to the ”Richtlinien für den Verkehrslärmschutz an Bundesfernstraßen in der Baulast des Bundes – VLärmSchR 97” (Guidelines for the Traffic Noise Control on Federal Highways Subject to Federal Maintenance) via a voluntary undertaking of the Federal Transport Minister.

Noise abatement, especially by means of sound-proofing windows, are possible if the assessment level exceeds the following limits:

Tab. 2: Overall Limits for the Traffic Noise Control on Federal Highways Subject to Federal Maintenance

Most possible sound abatement measures provided for in these guidelines have been implemented in Berlin.

Given certain preconditions, noise abatement measures in the area of road traffic are also possible under traffic regulations as per § 45 StVO.

Rules applicable to this area are to be found in the ”Vorläufigen Richtlinien des Bundesministeriums für Verkehr für straßenverkehrsrechtliche Maßnahmen zum Schutz der Bevölkerung vor Lärm” (Transport Ministry Provisional Guidelines for Traffic Regulatory Measures for Protection against Noise).

The day/night – guidelines lie at about 70/60 dB(A) for residential areas and installations which are similarly worthy of protection as well as 75/65 dB(A) for core, village, mixed and small business areas.