The Ultimate Glossary of Vibration Terminologies [PDF]


Vibration is a common phenomenon that occurs in various mechanical systems, such as machines and structures. It can be defined as the oscillation of an object around its equilibrium position. Vibration can be classified into different types based on various parameters, such as the direction of motion, the frequency of oscillation, and the amplitude of oscillation. Some of the common terminologies associated with vibration include natural frequency, resonance, damping, and amplitude.

Understanding these terminologies is crucial in the field of mechanical engineering, as they play a significant role in analyzing and designing mechanical systems that are robust and reliable. In this article, we will provide a short introduction to vibration and its terminologies, and explain their significance in the field of mechanical engineering.

What is Vibration?

Vibration refers to the oscillation, shaking, or movement of an object or a system of objects, back and forth or up and down, around a fixed or moving point. It can be caused by various factors such as mechanical friction, electrical current, sound waves, and seismic activity. Vibration can be measured and analyzed using specialized instruments such as accelerometers or vibration meters, and it is commonly expressed in terms of frequency, amplitude, and acceleration.

Vibration can have both positive and negative effects, depending on its nature and intensity. For example, it can be beneficial in some industrial applications, such as mixing, conveying, and sorting, but it can also cause damage, discomfort, or noise pollution in other contexts, such as transportation, construction, or healthcare. Therefore, it is important to understand the principles of vibration and how to control or mitigate its effects.

Vibration Terminology

Vibration terminology consists of 12 terms which are as follows:

  1. Periodic Motion
  2. Time Period
  3. Cycle
  4. Frequency
  5. Amplitude
  6. Natural Frequency
  7. The fundamental mode of vibration
  8. Degree of freedom
  9. Simple harmonic motion
  10. Damping
  11. Resonance
  12. Mechanical System
Vibration Terminology

Periodic Motion

The world of vibration analysis and engineering is filled with a wide range of terminologies, each with a specific definition and purpose. One of the most fundamental concepts in this field is periodic motion, which is the type of motion that occurs when an object moves in a repeated pattern or cycle.

Time Period

The time it takes for one complete cycle of periodic motion to occur is known as the time period. This is typically measured in seconds and is denoted by the symbol ‘T’. The time period is a crucial factor in understanding and analyzing the behavior of mechanical systems, as it helps to determine the frequency of the motion.


A cycle, on the other hand, refers to a single occurrence of the periodic motion. For instance, if a pendulum swings back and forth, one complete swing from one side to the other and back again is considered a cycle. The number of cycles that occur in a given time period is directly related to the frequency of the motion.


Frequency is defined as the number of cycles described in one second. It is typically measured in Hertz (Hz) and is denoted by the symbol ‘f’. The frequency of the motion is directly related to the time period, with a higher frequency indicating that more cycles occur within a given time period.


Amplitude refers to the maximum displacement of an object from its equilibrium position during a cycle of periodic motion. In other words, it is the distance between the highest and lowest points of the motion. This is typically measured in meters or millimeters and is denoted by the symbol ‘A’. The amplitude of the motion is directly related to the energy of the system, with a higher amplitude indicating a greater amount of energy being transferred during the motion.

Natural frequency

Natural frequency is the frequency at which an object vibrates when it is stimulated by an external force. This is also known as the resonant frequency, as it is the frequency at which the object resonates most strongly. The natural frequency of an object is determined by its size, shape, and material properties, and is a crucial factor in understanding how the object will respond to external stimuli.

The fundamental mode of vibration

The fundamental mode of vibration is the simplest form of vibration that a mechanical system can exhibit. It is when the system vibrates at a single frequency, which is also known as the natural frequency of the system. The fundamental mode of vibration is the most important mode of vibration and is used as a basis for analyzing the dynamic behavior of the system.

Degree of Freedom

Degree of freedom is the number of independent variables that are required to describe the motion of a system. It is a measure of the number of ways in which a system can move. A degree of freedom can be translational, rotational or a combination of both. The degree of freedom of a system is important in determining its natural frequency and its response to external forces.

Simple Harmonic Motion

Simple harmonic motion is a type of vibration in which the motion of the system follows a sinusoidal pattern. It is characterized by a constant amplitude and frequency. Simple harmonic motion is an important concept in the analysis of mechanical systems and is used to model the behavior of many systems.


It is resistance to the motion of a vibrating body. The vibration associated with the resistance is known as Damped Vibration. Damping is important in controlling the amplitude of the vibration and preventing damage to the system.


Resonance is a phenomenon that occurs when a system is excited at its natural frequency. It is characterized by a large amplitude of vibration and can lead to damage or failure of the system. Resonance is an important consideration in the design of mechanical systems and can be avoided by careful design and selection of materials.

Mechanical System

Mechanical systems are structures that are designed to perform specific functions. They can be simple or complex and can consist of various components such as springs, dampers, and masses. Mechanical systems are subject to vibration and can exhibit complex behavior under different conditions. Understanding the vibration behavior of mechanical systems is important in designing and analyzing these structures.

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Why is there vibration when braking at high speed?

One of the most common reasons for vibrations when braking at high speeds is warped brake rotors. A rotor is a disc-shaped component that spins along with the wheel and is clamped by the brake pads to slow down the vehicle. Over time, due to excessive heat and wear, the rotor can become warped, causing uneven contact with the brake pads, and hence, vibrations. This issue can be resolved by replacing the damaged rotors with new ones.

Another reason for vibrations when braking at high speeds is worn-out brake pads. Brake pads are the components that press against the rotors to stop the vehicle. Over time, due to wear and tear, the brake pads can become thin, causing uneven pressure on the rotors, which leads to vibrations. This issue can be resolved by replacing the old brake pads with new ones.

Moreover, loose or damaged suspension components can also cause vibrations when braking at high speeds. The suspension system of a vehicle comprises various components, such as shocks, struts, and springs, which absorb the shocks and bumps while driving. If any of these components are loose or damaged, it can cause vibrations, especially when braking at high speeds. This issue can be resolved by repairing or replacing the damaged suspension components.

Lastly, the tires of a vehicle can also cause vibrations when braking at high speeds. If the tires are worn out or improperly balanced, it can cause uneven contact with the road, leading to vibrations. This issue can be resolved by replacing the old tires with new ones or getting them balanced properly.

In conclusion, vibrations when braking at high speeds can occur due to various reasons, such as warped rotors, worn-out brake pads, loose suspension components, or improperly balanced tires. It is essential to identify the root cause of the vibrations and take appropriate measures to prevent any accidents. Regular maintenance and inspection of the braking system and suspension components can help prevent such issues from occurring.

Why is there vibration when accelerating at low speeds?

If you’ve ever noticed a vibration or shaking sensation when accelerating at low speeds, you’re not alone. This is a common issue that many drivers experience, and there are a few different reasons why it can happen. One possible cause of vibration during acceleration is a problem with your vehicle’s suspension system. If your suspension is worn or damaged, it can cause your car to vibrate or shake when you accelerate. This is because the suspension is responsible for absorbing the shocks and vibrations that come with driving, and if it’s not functioning properly, those vibrations can transfer to the rest of the vehicle.

Another possible cause of vibration during acceleration is an issue with your vehicle’s tires. If your tires are worn or out of balance, they can cause your car to vibrate or shake when you accelerate at low speeds. This is because the tires are responsible for providing traction and stability to your vehicle, and if they’re not properly balanced or aligned, they can create uneven pressure on the wheels, leading to vibration.

Finally, it’s also possible that the vibration you’re experiencing during acceleration is simply due to the way your vehicle is designed. Some cars are built with a more aggressive or sporty suspension, which can lead to more vibration and noise when accelerating at low speeds. Additionally, some vehicles have more powerful engines, which can create more vibration as well.

Regardless of the cause of your vibration during acceleration, it’s important to address the issue as soon as possible. Not only can it be annoying and uncomfortable for you and your passengers, but it can also be a sign of a more serious problem with your vehicle. If you’re experiencing vibration or shaking during acceleration, it’s a good idea to have your car inspected by a professional mechanic to determine the cause and find a solution.

How vibration is measured?

Vibration measurement is a critical process in a wide range of industries, including manufacturing, transportation, and construction. The goal of vibration measurement is to determine the level of vibration in a given system, which can help identify potential problems or areas for improvement. To measure vibration, specialized instruments known as vibration sensors are used. These sensors are typically mounted on the equipment or structure being measured and can detect vibration in various directions and frequencies.

In terms of the actual measurement process, vibration sensors generate electrical signals that correspond to the level of vibration being detected. These signals are then analyzed by specialized software that can provide a range of information, including the frequency, amplitude, and direction of the vibration. The data collected from vibration sensors can be used to identify potential issues, such as worn bearings, misaligned or unbalanced machines, or other sources of excessive vibration.

There are several different types of vibration sensors available, each with its own strengths and weaknesses. For example, piezoelectric sensors generate electrical signals when subjected to mechanical stress, while accelerometers measure changes in velocity to determine vibration levels. Other types of sensors include velocity sensors, displacement sensors, and proximity sensors, each of which has its own unique characteristics and applications.

In conclusion, vibration measurement is a critical process for ensuring the safe and efficient operation of a wide range of equipment and structures. By utilizing specialized sensors and software, engineers and technicians can accurately measure vibration levels and identify potential issues before they become major problems.


In conclusion, vibration is a complex phenomenon that is widely used in various industries such as automotive, aerospace, and civil engineering. Understanding the different terminologies associated with vibration is crucial for professionals working in these fields. The terminologies discussed in this article, such as amplitude, frequency, and phase, are essential for analyzing and measuring vibrations accurately.

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