Die Messung der Schwingungsfrequenz
Frequency is one of the most important parameters in vibration monitoring. Understanding how it is measured helps you interpret compliance reports, set correct thresholds, and protect structures more effectively.
Every vibration has two defining characteristics: how fast the motion occurs (frequency) and how intense it is (amplitude). Standards like DIN 4150-3 and SBR-A do not simply set a single velocity limit. They set limits that change depending on frequency. Without accurate frequency measurement, compliance assessment is impossible.
Was ist die Schwingungsfrequenz?
Frequency describes how many complete oscillation cycles occur per second. It is expressed in Hertz (Hz). A vibration at 10 Hz completes 10 full back-and-forth cycles every second. A vibration at 50 Hz completes fifty.
In practice, the vibrations caused by pile driving, demolition, or heavy machinery are not a single clean frequency. They contain a mix of frequencies at the same time. The dominant frequency is the one carrying the most energy. This is the frequency that monitoring systems extract for comparison against standard limit curves.
Kernkonzept: Dominante Frequenz is the frequency at which a vibration event carries its highest energy. Building standards use this value to select the correct limit from their frequency-dependent curves. Measuring PPV (Peak Particle Velocity) alone, without frequency, gives an incomplete and potentially misleading picture.
Warum die Frequenz für die Einhaltung der Vorschriften wichtig ist
Standards like DIN 4150-3, BS 7385-2, and SBR-A define limits as a curve rather than a single number. The allowable Peak Particle Velocity (PPV) at 5 Hz is very different from the allowable PPV at 50 Hz. Lower frequencies are generally more damaging to structures, so limits are stricter in that range.
This means a project on a soft-soil site producing low-frequency ground movement faces tighter constraints than a project with high-frequency vibration at the same PPV level. Getting the frequency wrong leads to either unnecessary work stoppages or actual risk to surrounding buildings.
| Standard | Frequenzbereich | Welche Änderungen kommen mit der Häufigkeit? |
|---|---|---|
| DIN 4150-3 | 1 bis 80 Hz | Die PPV-Grenze steigt mit der Häufigkeit für Industrie- und Gewerbegebäude. |
| SBR-A | 1 bis 100 Hz | Drei Vibrationsklassen mit frequenzabhängigen A1-Referenzwerten. |
| BS 7385-2 | 1 bis 250 Hz | Grenzkurven sind in Strukturen mit niedriger, mittlerer und hoher Empfindlichkeit unterteilt. |
| ISO 4866 | 0,1 bis 80 Hz | Methodische Referenz für Frequenzgewichtung und Filterung. |
Wie wird die Frequenz in der Praxis gemessen?
Modern vibration monitors measure frequency through signal processing. The sensor captures a continuous time-domain signal: a waveform that shows how particle velocity or acceleration changes over time. That raw signal is then analyzed to extract frequency content.
Der Sensor erfasst die Wellenform
A geophone or MEMS accelerometer records particle velocity or acceleration as an analog signal in three axes: vertical, transverse, and longitudinal.
Analog-zu-Digital-Wandlung
The continuous waveform is sampled at a high rate (typically several hundred to several thousand samples per second) and converted to a digital time series.
Schnelle Fourier-Transformation (FFT)
The logger applies an FFT to transform the time-domain signal into a frequency spectrum. This shows the amplitude at each frequency component present in the event.
Dominante Frequenzidentifikation
The system identifies the frequency with the highest spectral amplitude. This is stored as the dominant frequency alongside the PPV for each recorded event.
Vergleich mit der Grenzkurve
The monitoring system plots the measured PPV and dominant frequency against the applicable standard curve to determine compliance automatically.
Geofone vs. MEMS-Beschleunigungsmesser
The choice of sensor directly affects how accurately frequency is captured, particularly at the low end of the spectrum.
Geofon-Sensoren Electromechanical sensors with a natural frequency typically around 4.5 Hz. Very accurate in the 4 to 300 Hz range but begin to roll off below their natural frequency. A common source of missed low-frequency events in older systems.
MEMS-Beschleunigungssensoren Micro-electromechanical sensors with a flat response from near 0 Hz upward. Modern systems like the Vibra 5+ use MEMS combined with advanced signal processing to achieve accurate measurements from 0.5 Hz, covering frequencies that geophones often miss.
Dreihaxialer Messwert measurement Vibration frequency can differ per axis. A tri-axial sensor captures all three spatial directions simultaneously and reports the dominant frequency and PPV per axis as well as the resultant vector.
Niedrige Frequenz-Vibrationen: Ein kritischer Blickwinkel
Niedrigfrequente Schwingungen, typischerweise im Bereich von 1 bis 10 Hz, sind besonders relevant bei weichen Untergründen, während tiefer Fundamentarbeiten durchgeführt werden und bei sensiblen Bauteilen wie Denkmälern.
Low-frequency vibrations, typically in the 1 to 10 Hz range, are particularly relevant near soft soil conditions, during deep foundation work, and for sensitive structures like heritage buildings. Standards like SBR-A set their strictest limits precisely in this range.
A monitoring system that underperforms below 4 Hz can give the impression that measured values are safely within limits while the actual ground motion is significantly higher. This is one of the most common causes of disputed measurements on construction projects.
When selecting monitoring equipment, always check the specified lower frequency limit in the technical datasheet. For Dutch projects under SBR-A and for most DIN 4150-3 applications, a system capable of accurate measurement from 1 Hz or lower is the correct requirement.
Dreiaxiales Messen und Frequenz pro Achse
Ground and structural vibrations do not travel equally in all directions. A vibration event from pile driving will often show different dominant frequencies on the vertical axis compared to the horizontal axes. Compliance standards typically require assessment in all three directions separately and as a vector sum.
Relying on a single-axis sensor and hoping it captures the worst case introduces risk. Tri-axial systems record all three channels simultaneously, making it possible to identify which direction is driving the compliance result and to store complete raw traces for later review if a dispute arises.
Die Speicherung roher Spuren zur Streitbeilegung
A logging system that stores only peak values and dominant frequencies records enough information for routine compliance checks. But in the event of a damage claim or regulatory challenge, the raw time-domain trace is essential. It allows an independent expert to reprocess the data with any standard or filter and verify the original measurement independently.
Projects near sensitive buildings or in litigious environments should always configure their monitoring system to store full raw waveforms for all exceedance events and, ideally, for all significant events above a defined pre-trigger threshold.
Gängige Fehler bei der Frequenzmessung
Using a sensor with inadequate low-frequency response. A geophone with a natural frequency of 4.5 Hz will not accurately capture events dominated by 1 to 3 Hz content. This is especially problematic near soft soil or during vibrocompaction work.
Setting thresholds based on PPV alone. Without entering the applicable standard and the correct structure category, a monitor cannot automatically evaluate compliance. The threshold at 5 Hz and at 50 Hz are not the same number. Poor sensor coupling. A sensor that is not firmly attached to the structure or ground will introduce its own resonance and give a distorted frequency reading. Always follow the mounting instructions and verify coupling before measurement begins.
Not storing raw traces. If only processed peak results are saved, an independent technical review of a disputed event becomes impossible. Configure the system to store raw data from the start of the project.
Häufig gestellte Fragen
Welche Frequenzbereiche sind für den Schutz von Gebäuden am wichtigsten?
For building protection under DIN 4150-3 and SBR-A, the range from 1 to 50 Hz is most critical. Low-frequency content between 1 and 10 Hz is subject to the strictest limits. Systems that cannot measure reliably below 4 Hz risk missing the most damaging part of the vibration event.
Ist die Dominanzfrequenz die gleiche wie die Spitzenfrequenz?
These terms are often used interchangeably in construction monitoring. Both refer to the frequency at which the most energy is concentrated in a given event. In formal signal processing, the peak in the FFT spectrum corresponds to the dominant frequency used in compliance assessment.
Kann die Frequenz während einer Bauarbeit variieren?
Yes. The dominant frequency of ground vibration from pile driving, for example, can shift depending on the pile type, driving energy, and soil layering. This is why continuous logging rather than spot checks is the correct approach for compliance monitoring.
Brauche ich ein separates Instrument, um Frequenz und PPV zu messen?
No. Modern vibration monitors record both simultaneously from the same sensor. A single tri-axial logger will capture PPV and dominant frequency in all three axes and compare them to the selected standard automatically.
Welche Normen sollte ich bei einem niederländischen Bauprojekt anwenden?
SBR-A applies to nuisance assessment near residential buildings and SBR-B applies to structural damage risk. For projects with an international or German client or specification, DIN 4150-3 may also be required. Always confirm the applicable standard with the permit authority before starting measurement.
Genauigkeit von 0,5 Hz und höher
The Vibra 5+ uses MEMS technology combined with advanced processing to deliver reliable frequency and PPV measurement across the full range required by DIN 4150-3, SBR-A/B, and BS 7385-2. No low-frequency blind spots, no manual data retrieval, no gaps in your compliance record.
Wollen Sie sicherstellen, dass Ihre Vibrationsmessungen genau sind?
Wir helfen Ihnen, die richtige Ausrüstung auszuwählen und Frequenzdaten gemäß DIN 4150-3, SBR und BS 7385-2 zu interpretieren.