CVA Signal Processing & FFT Analysis

Question 1

What does FFT stand for in vibration analysis?

Accepted Answer

Fast Fourier Transform

Answer

FFT stands for Fast Fourier Transform, a mathematical algorithm that converts a time-domain signal into its frequency-domain components.

Question 2

What is aliasing in digital signal processing?

Accepted Answer

False frequencies appearing when the sampling rate is too low

Answer

Aliasing occurs when the sampling rate is insufficient (below twice the highest frequency of interest), causing high-frequency signals to appear as false low-frequency components.

Question 3

What is spectral leakage in FFT analysis?

Accepted Answer

Spreading of energy into adjacent frequency bins caused by non-integer cycles in the time record

Answer

Spectral leakage occurs when a signal's frequency does not fall exactly on an FFT bin, causing energy to spread into neighboring bins and masking nearby peaks.

Question 4

Which windowing function is most appropriate for analyzing synchronous (shaft-speed) vibration components?

Accepted Answer

Hanning window

Answer

The Hanning window is the most common general-purpose window for rotating machinery analysis as it provides a good balance between frequency resolution and leakage reduction.

Question 5

What is the frequency resolution of an FFT spectrum?

Accepted Answer

1 divided by the time record length

Answer

Frequency resolution equals 1 divided by the time record length (in seconds), so longer time records provide finer frequency resolution.

CVA - Certified Vibration Analyst Practice Test

CVA - Certified Vibration Analyst Practice Test

CVA Signal Processing & FFT Analysis