Vibrations , also known as shaking and chatter in English , are periodic (mechanical) vibrations of materials and bodies that are themselves elastic or consist of elastically connected individual parts or building blocks. In contrast to the term “ vibration ”, “ vibration ” suggests that the process can be heard or felt directly .
Many organisms have receptors that do not respond to simple touch, but to periodic mechanical stimuli (→ mechanoreceptors of the skin ). The transition from feeling to hearing is more gradual.
In the case of musical instruments , vibrations are initially understood to be the unwanted resonance of components that can produce interfering noises . Here, among other things serve felt - or leather cushion to dampen such effects. A distinction must be made between this and the intentional, periodically recurring, slight change in pitch , the vibrato .
Perception, senses, skin
In sensory physiology , vibrations are understood to be light shocks that are registered by special receptors ( Vater-Pacini bodies ). The vibration perception is part of the haptic perception and is assigned to the fine perception (epicritical sensitivity).
In classic massage , vibration is one of the five movements used there. The physical therapy uses high-strength and high-frequency vibrations (3 to 30 Hz) inter alia for mucus in the airways.
Effects on humans
In human perception, vibrations and shocks differ from audible noises. Accordingly, the delimitation can be made in the low-frequency range. The lower hearing threshold plays a decisive role here. The effect of inaudible low-frequency noises ( infrasound ) is examined, for example, with special musical instruments or infrasound generators. In connection with the noise of railways , especially due to the nocturnal freight traffic , an increase in complaints from residents can be observed - at least in Germany . In Germany, however, legal limit values only apply to occupational safety .
Depending on the frequency range and strength of the vibration, prolonged exposure, for example when working, can initially lead to general discomfort and later various symptoms such as pain in the abdomen or chest as well as back pain or headache. Years of exposure to vibrations can lead to damage to the lumbar spine and joints, depending on where they are exposed. Vibration-related circulatory disorders can also occur, especially in the hands (see Vibration-Related Vasospastic Syndrome ) . These injuries have been considered occupational diseases since 1993 .
Effects on physical bodies
Depending on the frequency range of the vibration, long-term mechanical vibrations (= constant vibration) can cause material fatigue. This usually takes place through intergranular (along the grain boundaries of the structure ) crack formation in materials under the simultaneous influence of a periodically changing tensile stress or with superimposed low-frequency tensile stress. This effect can be enhanced by the presence of a specific corrosion medium. The effects have therefore been studied for a long time. In the VDI guideline 2062 it was already stated in the 1970s: "Undesired vibrations and impacts are encountered in all technical fields, especially in the machine and electrical industry, traffic, construction and process engineering."
Research into the causes is also carried out in connection with damage to buildings . The Federal / State Working Group on Immission Control has put together extensive working instructions on this subject. It states: "There is no legally binding national clarification for plant operators and monitoring authorities as to when vibration immissions on structures and people in buildings are to be regarded as harmful environmental effects." Often, however, the subjective perception of those affected cannot be confirmed by measurements . An investigation by the State Office for Geology and Mining in Rhineland-Palatinate, which was carried out in 2013, had the following result: "A causal connection between traffic-related vibrations and mass movements (rockfalls and rock falls) on the Middle Rhine cannot be based on the available measurement results and investigations getting produced."*
The measures for combating vibrations differ fundamentally from those for combating noise . Vibrations often have similar causes and can often cause noise, but they have different propagation paths. The sound initially spreads directly through the air, while the shocks or vibrations through solid material. Vibrations can become audible for humans if, for example, components (ceilings, walls) radiate secondary airborne sound in the audible frequency range. Since the secondary noise partially undermines passive noise protection measures such as noise barriers or soundproof windows, protective measures at the source (emission) are more effective for these immissions (vibration, secondary noise). Measures at the source are aimed at machine foundations, railroad tracks, etc.
The ÖNORM S 9012 in Austria or the BEKS in Switzerland and Liechtenstein, for example, are used to assess vibration and secondary noise emissions. In Germany, the VDI Vibration Control Manual contains extensive descriptions and recommendations. Vibrations on and in buildings are determined and assessed in accordance with DIN series 4150; this series also contains requirements for reduction.
In order to make working in an environment with vibrations as bearable as possible, the following things should be taken into account when designing the workplace: If possible, rotating instead of oscillating machine parts should be used. Belt drives are preferable to chain drives . Drilling causes less vibration than punching , hammering or ramming . An electric drive runs with significantly less vibration than an internal combustion engine.
In addition, the workplace can also be protected by vibration isolation behind the vibration source. A distinction is made between active (vibration exciter is isolated) and passive (work area to be protected is isolated) isolation.
National occupational safety regulations, which are intended to avoid damage caused by vibrations, form the legal basis for measures to reduce vibrations. In Germany, for example, this is the Noise and Vibration Occupational Safety and Health Ordinance of March 2007.
- Noise (physics)
- Vibration training
- Vibration probe
- Human oscillations, vibrations or mechanical oscillations that affect people
- Vibration test
- Acceleration logger , for vibration measurements
- BAuA : Publications on the subject of "Effects of vibrations on humans"
- Institute for Occupational Safety and Health of the German Social Accident Insurance : Vibrations
- European Agency for Safety and Health at Work: Workplace exposure to vibration in Europe: an expert review
- ↑ a b Frank M. Rauch: Need for action in the case of low-frequency noises and vibrations? , Magazine for pollution control 4/2017
- ^ W. Mauritz, K. Steinreadyhner: Humidification of the breathing gas, physical therapy. In: J. Kilian, H. Benzer, FW Ahnefeld (ed.): Basic principles of ventilation. Springer, Berlin a. a. 1991, ISBN 3-540-53078-9 , 2nd, unaltered edition, ibid 1994, ISBN 3-540-57904-4 , pp. 304-313; here: p. 310 f.
- ↑ Infrasonic - haunted music?
- ↑ Making pure infrasound on a budget
- ↑ VDI guideline 2057 sheet 1, September 2002 edition, page 3
- ↑ VDI guideline 2062, sheet 1 draft , VDI Society for Construction and Development, July 1974
- ↑ Notes on measuring, assessing and reducing vibration emissions (resolution of the regional committee for pollution control of May 10, 2000) , published on the website of the Hessian State Office for Nature Conservation, Environment and Geology , accessed on November 7, 2018
- ^ Rail- related vibrations in the Middle Rhine Valley - website of the State Office for Geology and Mining , Rhineland-Palatinate, accessed on November 7, 2018
- ↑ VDI manual vibration technology. Association of German Engineers , accessed on December 18, 2018 .