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Understanding Decibels (dBs)

Vibration Experts

Half power point of a filter

Introduction

Understanding Decibels: This is a very short video that describes the “half power point” in a filter in terms of decibels (dBs) as well as the 0.707 voltage point. It will also describe the linear range of a vibration sensor in terms of it’s +- 3dB points.

Decibel units are frequently used in vibration analysis and sound measurements. We will explore the simple dB formulas and how to solve them. After watching this video you will have an understanding decibels and how a dB change relates to both power and the voltage coming off a sensor.

Understanding Decibels Formulas

These are the formulas we will review in the video to help with you understand decibels

V = Volts, V1 = Initial voltage, V2 = New voltage

P = Power, P1 = Initial Power, P2 = New Power

dB = 20 log (V2/V1)

dB = 10 log (P2/P1)

 V=√ (P2/P1) and P=(V2/V1)2

You will understand these formulas and you will understand why a drop of -3dB is called the “half power” point. You will also see how this change is reflected in vibration amplitude and how it relates to the voltages coming off of a sensor. This will also help you understand the use of the 3dB point in sensor calibration and in filters.

Watch on YouTube:

https://youtu.be/8rr3Vv7G8ZI

After watching the video you can test your knowledge with this short quiz: https://zencovibrations.com/decibels-filters-and-sensors-quiz/

If you enjoyed this content, please subscribe to my YouTube channel and share it. Also consider registering for an ISO 18436-2 Vibration Analysis Certification Course. You can see the public course schedule here: https://zencovibrations.com/shop you can contact me to schedule a private course on-site or online. Link to me on LinkedIN: https://www.linkedin.com/in/alanfriedmanvibe/