CVA Signal Processing & FFT Analysis

Question 1

What does FFT stand for in vibration analysis?

Accepted Answer

Fast Fourier Transform

Answer

Frequency Field Testing

Answer

Full Force Transmission

Answer

Filtered Frequency Trace

Question 2

What is aliasing in digital signal processing?

Accepted Answer

False frequencies appearing when the sampling rate is too low

Answer

Signal amplification above the Nyquist frequency

Answer

Overlap between adjacent frequency bins

Answer

Leakage of energy into neighboring spectral lines

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

Loss of signal energy due to sensor placement

Answer

Noise entering the spectrum from electrical interference

Answer

Attenuation of high-frequency components

Question 4

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

Accepted Answer

Hanning window

Answer

Flat Top window

Answer

Rectangular (uniform) window

Answer

Kaiser-Bessel window

Question 5

What is the frequency resolution of an FFT spectrum?

Accepted Answer

1 divided by the time record length

Answer

Sampling rate divided by the number of spectral lines

Answer

Maximum frequency divided by the number of averages

Answer

Bandwidth divided by the overlap percentage

Question 6

What is the purpose of averaging multiple FFT spectra?

Accepted Answer

To reduce random noise and improve the signal-to-noise ratio

Answer

To increase the maximum detectable frequency

Answer

To extend the frequency resolution beyond the Nyquist limit

Answer

To correct for transducer sensitivity variations