# Mechatronics Questions and Answers – Analog Signal Conditioning – Noise Reduction

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This set of Mechatronics Multiple Choice Questions & Answers (MCQs) focuses on “Analog Signal Conditioning – Noise Reduction”.

1. Which noise is also termed as multiplicative noise?
a) Gaussian Noise
b) Salt and pepper noise
c) Speckle noise
d) Linear noise

Explanation: Speckle noise is also termed as multiplicative noise. It occurs when some unwanted signal gets multiplied with the original signal during its transmission, receiving or during an other signal processing.

2. Who invented median filter?
a) Norbert wiener
b) Pitas
c) Charles young
d) Charles wheatstone

Explanation: Pitas invented median filter. It was developed in the year 1990. Median filters are widely used to remove speckle and pulse noises. It is a robust filter which is also used for image smoothers in variety of application.

3. Which filter should be used to remove speckle noise from an image?
a) Mean filter
b) Median filter
c) Gaussian filter
d) Weiner filter

Explanation: Weiner filter should be used to remove speckle noise from an image. It is most suitable filter for this purpose. Speckle noise generally degrades the quality of image taken from SAR (Synthetic aperture radar) or medical ultrasound.
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4. Which filter should be used to remove salt and pepper noise from an image?
a) Mean filter
b) Median filter
c) Gaussian filter
d) Weiner filter

Explanation: Median filter should be used to remove salt and pepper noise from an image. It is most suitable filter for this purpose. Morphological filters can also be used. Both the filters provide maximum noise reduction.

5. Mean filter is better than median filter.
a) True
b) False

Explanation: Median filter is better than mean filter. It is better because it does not create random and unrealistic pixel values on its own. It creates the pixel value which is actually present in the neighbourhood. It can preserve sharp image better than the mean filters.
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6. Noise reduction technique is only applicable for audio and other time varying signals.
a) True
b) False

Explanation: Noise reduction technique is not only applicable for audio and other time varying signals but also applicable for an image. The main aim of noise reduction technique is removing the unwanted signals and unwanted pixel intensity from audio and image respectively.

7. What is the full form of FPGA in terms of signal filtering and noise reduction technique?
a) Functionally programmable gate array
b) Function programmed gate array
c) Field programmable gate array
d) Field programmable gateway array

Explanation: FPGA in terms of signal filtering and noise reduction technique stands for Field programmable gate array. It can be used for removing the noise from the signal. It can contain thousands or millions of logic gates with programmable interconnections.

8. Which type of signal facilitates easier noise removal?
a) Digital Signal
b) Analog Signal
c) Random Signal
d) Sine Signal

Explanation: Digital Signal facilitates easier noise removal. It is easier so because in digital signal there is fixed magnitude of signal. The unwanted signal can be easily identified by their different magnitudes at different time intervals.

9. What is the full form of IIR in terms of signal filtering and noise reduction technique?
a) Infinite impulse response
b) Infinite impulse reduction
c) Infinite impulse recombination
d) Imperfect impulse response

Explanation: IIR in terms of signal filtering stands for Infinite impulse response. It is a digital filter. The Impulse response of this filter depends upon finite number of inputs and finite number of previous outputs of the filter. It is a combination of FIR (Finite impulse response) and previous output of the filter.

10. Which is an example of Power line filter?
a) MSP430G2ET
b) CMCP793V-500
c) SLB700A/06VA
d) FN2060A-6-06

Explanation: FN2060A-6-06 is an example of Power line filter. It is developed by Schaffner to attenuate frequencies between an electronic component and an external line. SLB700A/06VA is a force sensor. MSP430G2ET is a development board manufactured by the “TEXAS INSTRUMENTS” and CMCP793V-500 is a velocity sensor.

11. Who invented wiener filter?
a) Norbert wiener
b) Robert Wiener
c) Charles young
d) Charles wheatstone

Explanation: Norbert wiener invented wiener filter. The theory behind this filter was proposed by Norbert Wiener in the 1940’s. It was later published in the year 1949. This theory is often called as Wiener–Kolmogorov filtering theory because of significant work of Andrew Kolmogorov behind this.

12. Median filter removes the sharp edges from an image.
a) True
b) False

Explanation: Median filter does not remove the sharp edges from an image. It preserves those edges better than anyone else. Unlike mean filters it does not create unrealistic pixel values that will reduce the quality and sharpness of image.

13. Low pass filters removes the sharpness of an image.
a) True
b) False

Explanation: Low pass filters removes the sharpness of an image. It is a major disadvantage of low pass filters. For preserving the sharpness, generally median filters are used. Low pass filters blur the sharp edges.

14. Which noise is caused by voltage spikes?
a) Gaussian Noise
b) Salt and pepper noise
c) Impulse noise
d) Linear noise

Explanation: Impulse noise is caused by voltage spikes. These noises can cause error in the circuits used for data transmission. It can be tolerated by some circuits but can also cause trouble for other. Median filters are used to handle these types of noises.

15. Which filter should be used to remove impulse noises?
a) Mean filter
b) Median filter
c) Gaussian filter
d) Weiner filter

Explanation: Median filter should be used to remove impulse noises. It is most suitable filter and is widely used for this purpose. It is reliable as it removes the noises without damaging the desired edge details.

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