# Digital Communications Questions and Answers – Noise

This set of Digital Communication Interview Questions & Answers focuses on “Noise

1. Noise has
a) Infinite energy
b) Infinite power
c) Infinite energy & power
d) None of the mentioned

Explanation: Noise has infinite energy signal.

2. Thermal noise is
a) Energy signal
b) Power signal
c) Energy & Power signal
d) None of the mentioned

Explanation: Thermal noise is considered as power signal as it has infinite energy.

3. Thermal noise is a wide sense stationary process.
a) True
b) False

Explanation: Thermal noise is modeled as a wide sense stationary stochastic process.

4. The maximum likelihood function is
a) Positive
b) Negative
c) Any of the mentioned
d) None of the mentioned

Explanation: The maximum likelihood function is always positive.

5. Matched filtering operation includes
a) Spectral phase matching
b) Spectral amplitude matching
c) Spectral phase & amplitude matching
d) None of the mentioned

Explanation: The two procedures of matched filtering are spectral amplitude matching and spectral phase matching.

6. Matched filter is
a) Linear
b) Non linear
c) Linear & Non linear
d) None of the mentioned

Explanation: Matched filter is a linear filter.

7. Which consists of less ISI?
a) Nyquist filter
b) Raised cosine filter
c) Nyquist & Raised cosine filter
d) None of the mentioned

Explanation: Raised cosine filter results in less ISI than Nyquist filter.

8. Eigen functions are not orthogonal.
a) True
b) False

Explanation: An important property of eigen function is that they are orthogonal.

9. Shot noise is produced by
a) Electrons
b) Photons
c) Electrons & Photons
d) None of the mentioned

Explanation: Shot noise occurs due to particle like the behaviour of electron and photon.

10. Shot noise is avoidable when current is
a) Zero
b) One
c) Infinity
d) None of the mentioned

Explanation: Shot noise is avoidable only when the current is zero.

11. Shot noise is
a) Stochastic process
b) Poisson process
c) Stochastic & Poisson process
d) None of the mentioned

Explanation: Shot noise is a Poisson process.

12. Which occurs due to equilibrium fluctuations?
a) Thermal noise
b) Johnson noise
c) Thermal & Johnson noise
d) None of the mentioned

Explanation: Thermal noise is caused by oscillations in equilibrium. Johnson noise is another name for this noise.

13. Flicker noise is called as
a) White noise
b) Pink noise
c) Brown noise
d) None of the mentioned

Explanation: Flicker noise is called as pink noise.

14. Which has the same power spectral density?
a) White noise
b) Brown noise
c) White & Brown noise
d) None of the mentioned

Explanation: White noise has the same power spectral density as brown noise, however brown noise has a lower power spectral density.

15. Which noise is useful for dithering?
a) White noise
b) Pink noise
c) Brown noise
d) None of the mentioned

Explanation: Brown noise is sometimes useful for dithering.

16. Capacity of a channel can be increased by
a) Increasing channel bandwidth
b) Increasing signal power
c) Increasing channel bandwidth &signal power
d) None of the mentioned

Explanation: A channel’s capacity can be expanded by increasing channel bandwidth as well as signal power.

17. Capacity of the channel can be increased by reducing in band noise power.
a) True
b) False

Explanation: Capacity of a channel can be increased by reducing the in band noise power.

18. SQNR can be improved by _______ sampling rate.
a) Increasing
b) Decreasing
c) Does not depend
d) None of the mentioned

Explanation: SQNR can be improved by increasing the sampling rate.

19. Which offers better SQNR?
a) Delta modulation
b) PCM
c) Delta modulation & PCM
d) None of the mentioned

Explanation: PCM offers better SQNR than delta modulation.

20. Two functions are called as orthogonal if on integrating the product we get
a) One
b) Zero
c) Infinity
d) None of the mentioned

Explanation: If the integral value of integrating the product is zero, two functions are said to be orthogonal.

Noise is a wearables firm based in Gurugram, India. Noise prides itself on being “Made in India.” As of June 2020, Noise is one of India’s leading smart watch firms, and it is also one of the top five wireless earphone brands. If the integral value of integrating the product is zero, two functions are said to be orthogonal. Noise provides young Indian consumers with the most up-to-date personal technology accessories at a cheap price. For the past four years, we’ve been a bestselling brand on Amazon and Flipkart, and in 2019, Noise was the country’s largest seller of wireless earphones.