Q.1 Which of the following is a primary application of the Fast Fourier Transform (FFT) in audio signal processing?
Echo cancellation in telephone networks
Pitch detection for musical notes
Image edge detection
Radar target tracking
Explanation - FFT converts time‑domain audio into its frequency components, allowing the fundamental frequency (pitch) of musical notes to be identified.
Correct answer is: Pitch detection for musical notes
Q.2 In digital image processing, which technique uses 2‑D convolution to enhance edges?
Histogram equalization
Sobel operator
Lempel‑Ziv compression
Phase‑locked loop
Explanation - The Sobel operator applies a pair of 3×3 convolution kernels to approximate the gradient of image intensity, highlighting edges.
Correct answer is: Sobel operator
Q.3 Which modulation scheme benefits most from pulse‑shaping filters such as the raised‑cosine filter?
Amplitude Shift Keying (ASK)
Frequency Shift Keying (FSK)
Quadrature Amplitude Modulation (QAM)
On‑Off Keying (OOK)
Explanation - Raised‑cosine filters limit inter‑symbol interference in high‑order constellations like QAM, preserving symbol integrity.
Correct answer is: Quadrature Amplitude Modulation (QAM)
Q.4 What is the main advantage of using wavelet transform over Fourier transform in biomedical signal analysis?
Higher computational speed
Better time‑frequency localization
Simpler hardware implementation
Elimination of noise without filtering
Explanation - Wavelets provide multi‑resolution analysis, capturing both high‑frequency details and low‑frequency trends simultaneously, which is crucial for non‑stationary biomedical signals like ECG.
Correct answer is: Better time‑frequency localization
Q.5 Which of the following is a typical use of adaptive filtering in acoustic echo cancellation?
Detecting speech presence
Estimating room impulse response
Compressing audio data
Enhancing bass frequencies
Explanation - Adaptive filters such as LMS continuously estimate the echo path (room impulse response) to subtract the echo from the microphone signal.
Correct answer is: Estimating room impulse response
Q.6 In a communication system, what is the purpose of a matched filter at the receiver?
To increase the bandwidth of the received signal
To maximize the signal‑to‑noise ratio (SNR)
To convert analog signals to digital
To perform error correction coding
Explanation - A matched filter correlates the incoming signal with a known template, providing the optimum SNR for detection in white Gaussian noise.
Correct answer is: To maximize the signal‑to‑noise ratio (SNR)
Q.7 Which compression technique is widely used for speech signals in mobile telephony?
JPEG
MPEG‑4
Linear Predictive Coding (LPC)
H.264
Explanation - LPC models the vocal tract and encodes speech efficiently, making it suitable for low‑bit‑rate mobile communication.
Correct answer is: Linear Predictive Coding (LPC)
Q.8 What is the primary function of a Kalman filter in radar signal processing?
Detecting the presence of a target
Estimating the target's position and velocity over time
Compressing radar echo data
Generating synthetic aperture images
Explanation - Kalman filters recursively combine noisy measurements with a dynamic model to produce optimal estimates of a target's state.
Correct answer is: Estimating the target's position and velocity over time
Q.9 Which of the following is a common application of digital signal processing in power systems?
Load forecasting using neural networks
Harmonic analysis of voltage and current waveforms
Design of high‑frequency transformers
Physical layout of transmission lines
Explanation - DSP techniques such as FFT are used to identify and quantify harmonics, helping improve power quality and filter design.
Correct answer is: Harmonic analysis of voltage and current waveforms
Q.10 In image compression, what does the term 'blockiness' refer to?
Loss of color fidelity
Visible borders between quantized DCT blocks
Blurring of edges due to low‑pass filtering
Noise introduced by sensor heating
Explanation - Blockiness occurs when each 8×8 DCT block is quantized separately, leading to discontinuities at block boundaries, especially at low bitrates.
Correct answer is: Visible borders between quantized DCT blocks
Q.11 Which algorithm is commonly used for speech recognition to model temporal sequences?
K‑means clustering
Hidden Markov Model (HMM)
Fast Fourier Transform (FFT)
Butterworth filter design
Explanation - HMMs capture probabilistic transitions between phonetic states, making them suitable for modeling speech over time.
Correct answer is: Hidden Markov Model (HMM)
Q.12 What is the purpose of a notch filter in biomedical signal processing?
To enhance high‑frequency components
To remove a specific narrowband interference (e.g., 60 Hz mains hum)
To increase the overall gain of the signal
To convert analog ECG to digital form
Explanation - A notch filter attenuates a narrow frequency band, commonly used to eliminate power‑line interference from ECG recordings.
Correct answer is: To remove a specific narrowband interference (e.g., 60 Hz mains hum)
Q.13 Which of the following best describes the use of DSP in seismic exploration?
Generating synthetic seismograms
Filtering out surface noise and extracting reflection events
Designing drilling equipment
Controlling the depth of boreholes
Explanation - DSP techniques such as band‑pass filtering and deconvolution are applied to seismic traces to isolate subsurface reflections from noise.
Correct answer is: Filtering out surface noise and extracting reflection events
Q.14 In OFDM (Orthogonal Frequency Division Multiplexing), why is a cyclic prefix added to each symbol?
To increase data rate
To simplify FFT implementation
To mitigate inter‑symbol interference caused by multipath
To encode error‑correction bits
Explanation - The cyclic prefix acts as a guard interval, preserving orthogonality among sub‑carriers even when delayed copies of the signal arrive.
Correct answer is: To mitigate inter‑symbol interference caused by multipath
Q.15 Which signal processing technique is primarily used for image denoising while preserving edges?
Median filtering
Uniform averaging
Laplacian sharpening
Fourier magnitude scaling
Explanation - Median filters replace each pixel with the median of its neighborhood, effectively removing impulse noise while maintaining edge structures.
Correct answer is: Median filtering
Q.16 What is the main advantage of using a digital FIR filter over an IIR filter in real‑time audio effects?
FIR filters have linear phase response
IIR filters require less computation
FIR filters can achieve infinite gain
IIR filters are always stable
Explanation - Linear phase ensures that all frequency components are delayed equally, preserving the waveform shape—critical for high‑fidelity audio.
Correct answer is: FIR filters have linear phase response
Q.17 In video compression standards like H.264, what is the purpose of motion estimation?
To detect scene changes
To predict and encode only the differences between successive frames
To increase color depth
To convert video to audio
Explanation - Motion estimation finds matching blocks across frames, allowing only residual data to be transmitted, which reduces bitrate.
Correct answer is: To predict and encode only the differences between successive frames
Q.18 Which of the following is a common use of the Discrete Cosine Transform (DCT) in signal processing?
Time‑domain echo cancellation
Image and video compression
Generating random noise
Designing analog filters
Explanation - DCT concentrates most of the signal energy into a few low‑frequency coefficients, making it ideal for compressing visual data.
Correct answer is: Image and video compression
Q.19 What does the term 'sampling rate' refer to in digital audio processing?
The number of bits per sample
The frequency range of human hearing
The number of samples taken per second
The amplitude resolution of the ADC
Explanation - Sampling rate, measured in Hz, defines how often the continuous audio waveform is measured to create a discrete representation.
Correct answer is: The number of samples taken per second
Q.20 Which of the following applications uses the concept of beamforming?
Acoustic echo cancellation
Wireless microphone arrays
Image histogram equalization
Digital video playback
Explanation - Beamforming combines signals from multiple microphones to steer the sensitivity pattern toward a desired direction while suppressing noise.
Correct answer is: Wireless microphone arrays
Q.21 In ECG signal analysis, what does the QT interval represent?
Time between atrial depolarization and repolarization
Duration of ventricular depolarization and repolarization
Interval of atrial contraction only
Period of isoelectric baseline
Explanation - The QT interval spans from the start of the Q wave to the end of the T wave, reflecting total ventricular electrical activity.
Correct answer is: Duration of ventricular depolarization and repolarization
Q.22 Which DSP technique is used to reduce the data rate of a sensor network while preserving essential information?
Time‑division multiplexing
Data quantization and compression
Phase‑locked loops
Analog filtering
Explanation - Quantization reduces the number of bits per sample, and compression eliminates redundancy, together lowering transmission bandwidth.
Correct answer is: Data quantization and compression
Q.23 What is the purpose of the 'pre‑emphasis' filter in speech processing?
To boost low‑frequency components
To attenuate high‑frequency noise
To amplify high‑frequency components
To normalize the overall signal power
Explanation - Pre‑emphasis compensates for the natural roll‑off of the speech spectrum, improving the signal‑to‑noise ratio for high‑frequency formants.
Correct answer is: To amplify high‑frequency components
Q.24 In the context of wireless communications, what does the term 'channel equalization' refer to?
Increasing the transmission power
Compensating for distortion introduced by the channel
Encrypting the transmitted data
Modulating the carrier frequency
Explanation - Equalizers reverse the effects of multipath fading and frequency-selective attenuation, restoring the original signal shape.
Correct answer is: Compensating for distortion introduced by the channel
Q.25 Which of the following is a typical use of the Hilbert transform in signal processing?
Generating analytic signals for envelope detection
Designing FIR filters
Compressing audio streams
Performing FFT on real‑time data
Explanation - The Hilbert transform creates a 90° phase‑shifted version of a signal, forming an analytic signal whose magnitude gives the envelope.
Correct answer is: Generating analytic signals for envelope detection
Q.26 What is the main advantage of using a polyphase filter bank in multirate signal processing?
Reduced computational load for decimation/interpolation
Higher filter order without increasing delay
Simplified hardware for analog signals
Improved frequency resolution of the FFT
Explanation - Polyphase structures split the filter into sub‑filters, allowing efficient processing when changing sampling rates.
Correct answer is: Reduced computational load for decimation/interpolation
Q.27 In a digital communication receiver, what does the Viterbi algorithm provide?
Fast Fourier Transform computation
Maximum likelihood sequence estimation for convolutional codes
Adaptive noise cancellation
Signal amplitude normalization
Explanation - The Viterbi algorithm finds the most probable transmitted bit sequence given the received noisy observations, used in decoding convolutional codes.
Correct answer is: Maximum likelihood sequence estimation for convolutional codes
Q.28 Which of the following is a characteristic of a linear-phase FIR filter?
Constant group delay across the passband
Infinite impulse response
Non‑causal behavior
Variable amplitude response
Explanation - Linear-phase filters have symmetric impulse responses, resulting in a constant time delay for all frequencies within the passband.
Correct answer is: Constant group delay across the passband
Q.29 What is the primary role of a 'scrambler' in digital data transmission?
To encrypt the data for security
To randomize the data pattern to avoid long runs of zeros or ones
To increase the signal power
To compress the data before transmission
Explanation - Scramblers prevent baseline wander and enable reliable clock recovery by ensuring a balanced number of transitions.
Correct answer is: To randomize the data pattern to avoid long runs of zeros or ones
Q.30 In the context of audio effects, what does a 'reverb' processor simulate?
The distortion caused by overdriven amplifiers
The reflection of sound in an acoustic space
The compression of dynamic range
The equalization of frequency bands
Explanation - Reverb adds delayed and attenuated copies of the original signal to mimic how sound bounces off surfaces in a room or hall.
Correct answer is: The reflection of sound in an acoustic space
Q.31 Which signal processing operation is used to convert a non‑stationary signal into a stationary one for easier analysis?
Differencing (first-order derivative)
Zero‑padding
Upsampling
Amplitude scaling
Explanation - Differencing removes trends and makes many signals stationary, which is a prerequisite for many spectral analysis methods.
Correct answer is: Differencing (first-order derivative)
Q.32 In image processing, which technique is used to reduce the size of an image while preserving important features?
Downsampling with anti‑aliasing filter
Zero‑order hold interpolation
Adding Gaussian noise
Histogram stretching
Explanation - An anti‑aliasing (low‑pass) filter removes high‑frequency components before downsampling, preventing aliasing artifacts.
Correct answer is: Downsampling with anti‑aliasing filter
Q.33 What is the primary benefit of using a 'logarithmic' (dB) scale for representing frequency spectra?
It linearizes the phase response
It compresses the dynamic range making small components more visible
It removes noise from the spectrum
It increases the resolution of high frequencies
Explanation - A decibel scale maps large variations in magnitude to a manageable range, highlighting weak spectral components.
Correct answer is: It compresses the dynamic range making small components more visible
Q.34 Which of the following is an example of a time‑frequency representation used in signal analysis?
Spectrogram
Impulse response
Transfer function
Phase diagram
Explanation - A spectrogram shows how the frequency content of a signal evolves over time, using short‑time Fourier transforms.
Correct answer is: Spectrogram
Q.35 In a digital audio workstation (DAW), what does the 'gain' control typically adjust?
The sampling rate of the audio file
The amplitude (volume) of the signal
The frequency response of the equalizer
The latency of the audio buffer
Explanation - Gain changes the signal's magnitude without altering its frequency content, affecting perceived loudness.
Correct answer is: The amplitude (volume) of the signal
Q.36 Which method is commonly used to estimate the power spectral density (PSD) of a random signal?
Welch's averaged periodogram method
Zero‑crossing detection
Peak detection algorithm
Linear predictive coding
Explanation - Welch's method reduces variance by averaging periodograms from overlapping, windowed segments of the signal.
Correct answer is: Welch's averaged periodogram method
Q.37 What is the main function of a 'low‑pass filter' in audio signal processing?
To increase the volume of high frequencies
To allow low frequencies to pass while attenuating high frequencies
To convert analog audio to digital
To shift the audio spectrum upward
Explanation - Low‑pass filters block high‑frequency components, which can be used for bass enhancement or noise reduction.
Correct answer is: To allow low frequencies to pass while attenuating high frequencies
Q.38 Which of the following is a typical use of the autocorrelation function in signal processing?
Detecting periodicity in a signal
Compressing an image
Generating random numbers
Designing a digital-to-analog converter
Explanation - Autocorrelation measures similarity between a signal and a delayed version of itself, revealing repeating patterns.
Correct answer is: Detecting periodicity in a signal
Q.39 In a GPS receiver, which signal processing technique is essential for acquiring satellite signals?
Matched filtering with known PRN codes
Time‑division multiplexing
Phase‑locked loop tracking only
Amplitude modulation detection
Explanation - GPS satellites transmit pseudo‑random noise (PRN) codes; matched filtering correlates the incoming signal with these codes to acquire and lock onto satellites.
Correct answer is: Matched filtering with known PRN codes
Q.40 What does the term 'bit‑error rate' (BER) quantify in a digital communication system?
The number of bits transmitted per second
The ratio of incorrectly received bits to total transmitted bits
The amount of power consumed by the transmitter
The bandwidth required for transmission
Explanation - BER measures the reliability of a communication link by indicating how many bits are in error after transmission.
Correct answer is: The ratio of incorrectly received bits to total transmitted bits
Q.41 Which of the following best describes the function of a 'decoder' in a digital communication system?
Convert analog signals to digital
Recover the original bit sequence from the coded data
Increase the signal’s amplitude
Shift the carrier frequency
Explanation - Decoders reverse the operation of encoders (e.g., error‑correcting codes) to retrieve the transmitted information.
Correct answer is: Recover the original bit sequence from the coded data
Q.42 In a radar system, what does the term 'Doppler shift' indicate?
Change in signal amplitude due to distance
Frequency change caused by relative motion between radar and target
Time delay of the reflected pulse
Polarization change of the transmitted wave
Explanation - Doppler shift is used to estimate target velocity by measuring the frequency difference between transmitted and received signals.
Correct answer is: Frequency change caused by relative motion between radar and target
Q.43 Which transform is most commonly used for image compression in the JPEG standard?
Discrete Fourier Transform (DFT)
Discrete Cosine Transform (DCT)
Wavelet Transform
Hartley Transform
Explanation - JPEG applies an 8×8 block DCT to decorrelate pixel values, enabling efficient quantization and entropy coding.
Correct answer is: Discrete Cosine Transform (DCT)
Q.44 What is the purpose of using a 'pilot tone' in OFDM transmission?
To carry user data
To provide a reference for channel estimation
To increase the overall data rate
To encrypt the transmitted signal
Explanation - Pilot tones are known symbols inserted into the OFDM frame, allowing the receiver to estimate and correct channel impairments.
Correct answer is: To provide a reference for channel estimation
Q.45 In speech enhancement, what does the term 'spectral subtraction' refer to?
Removing the estimated noise spectrum from the noisy speech spectrum
Subtracting the fundamental frequency from the signal
Eliminating silent segments from the audio
Increasing the amplitude of high‑frequency components
Explanation - Spectral subtraction estimates noise during non‑speech periods and subtracts it from the noisy speech spectrum to improve intelligibility.
Correct answer is: Removing the estimated noise spectrum from the noisy speech spectrum
Q.46 Which of the following is a key advantage of using a 'digital lock‑in amplifier'?
It can demodulate any frequency without a reference
It extracts the amplitude and phase of a signal at a specific reference frequency even in noisy environments
It increases the bandwidth of the input signal
It automatically compresses the signal
Explanation - Digital lock‑in amplifiers multiply the input with a reference and low‑pass filter to isolate the desired component, rejecting out‑of‑band noise.
Correct answer is: It extracts the amplitude and phase of a signal at a specific reference frequency even in noisy environments
Q.47 What does the term 'Nyquist rate' refer to in the context of sampling?
The minimum sampling frequency required to avoid aliasing, equal to twice the highest signal frequency
The maximum power a system can handle
The number of bits per sample
The latency of an ADC
Explanation - According to the Nyquist theorem, sampling at twice the maximum frequency ensures accurate reconstruction of the original analog signal.
Correct answer is: The minimum sampling frequency required to avoid aliasing, equal to twice the highest signal frequency
Q.48 In the context of audio codecs, what is the main difference between lossless and lossy compression?
Lossless compression reduces file size more than lossy compression
Lossy compression discards some audio information, while lossless compression preserves all original data
Lossless compression only works for speech, while lossy works for music
Lossy compression is reversible, lossless is not
Explanation - Lossy codecs (e.g., MP3) remove inaudible components for greater compression; lossless codecs (e.g., FLAC) retain exact original samples.
Correct answer is: Lossy compression discards some audio information, while lossless compression preserves all original data
Q.49 Which algorithm is widely used for image edge detection due to its ability to compute gradient magnitude and direction efficiently?
Canny edge detector
K-means clustering
FFT
LMS adaptive filter
Explanation - Canny uses Gaussian smoothing, gradient computation, non‑maximum suppression, and hysteresis thresholding to produce thin, well‑localized edges.
Correct answer is: Canny edge detector
Q.50 What is the primary purpose of a 'digital down‑converter' (DDC) in a software‑defined radio (SDR) receiver?
To increase the carrier frequency
To translate a high‑frequency band to baseband and reduce the sampling rate
To amplify the incoming RF signal
To encode the signal for transmission
Explanation - A DDC mixes the desired channel with a local oscillator, filters it, and decimates the result, simplifying further processing.
Correct answer is: To translate a high‑frequency band to baseband and reduce the sampling rate
Q.51 In image processing, which technique is used to reduce the amount of data required to represent an image while keeping visual quality high?
Upsampling
Quantization and entropy coding
Adding Gaussian blur
Temporal aliasing
Explanation - After transform coding (e.g., DCT), coefficients are quantized and then entropy coded (e.g., Huffman), achieving compression with minimal quality loss.
Correct answer is: Quantization and entropy coding
Q.52 Which of the following is a typical application of the MUSIC algorithm?
Estimating the direction of arrival (DOA) of multiple signals
Compressing video streams
Designing low‑pass FIR filters
Generating pseudo‑random sequences
Explanation - MUSIC exploits the eigenstructure of the covariance matrix to resolve closely spaced sources in array signal processing.
Correct answer is: Estimating the direction of arrival (DOA) of multiple signals
Q.53 In the context of digital filter design, what does the term 'stability' refer to?
The filter's ability to process high‑frequency signals
The location of poles inside the unit circle for IIR filters
The linear phase response of the filter
The speed at which the filter can be computed
Explanation - An IIR filter is stable if all its poles lie within the unit circle in the Z‑plane, ensuring bounded output for bounded input.
Correct answer is: The location of poles inside the unit circle for IIR filters
Q.54 Which of the following best describes the function of a 'digital phase‑locked loop' (DPLL) in communications?
To convert digital signals to analog form
To lock onto the phase and frequency of an incoming carrier signal
To increase the sampling rate of the received signal
To encrypt the transmitted data
Explanation - A DPLL tracks the carrier's phase and frequency, providing timing recovery and carrier synchronization for demodulation.
Correct answer is: To lock onto the phase and frequency of an incoming carrier signal
Q.55 What is the primary reason for applying a 'window function' before performing an FFT on a finite‑length signal segment?
To increase the signal's amplitude
To reduce spectral leakage caused by discontinuities at the segment edges
To convert the signal from time to frequency domain
To remove noise completely
Explanation - Windowing smooths the edges of the data block, minimizing leakage and producing a more accurate spectral estimate.
Correct answer is: To reduce spectral leakage caused by discontinuities at the segment edges
Q.56 In biomedical signal processing, which technique is commonly used to detect QRS complexes in ECG recordings?
Wavelet transform based detection
Linear predictive coding
Amplitude modulation
Frequency hopping
Explanation - Wavelet analysis captures the sudden changes in ECG that correspond to QRS complexes, allowing robust detection even with noise.
Correct answer is: Wavelet transform based detection
Q.57 Which of the following describes a 'polyphase implementation' of an FIR filter used in a decimator?
Splitting the filter into multiple sub‑filters that operate on interleaved input samples
Increasing the filter order to improve stop‑band attenuation
Using analog components to implement the filter
Applying a Fourier transform before filtering
Explanation - Polyphase structures enable efficient computation by processing only the necessary samples after downsampling.
Correct answer is: Splitting the filter into multiple sub‑filters that operate on interleaved input samples
Q.58 In the context of audio signal processing, what does the term 'dynamic range compression' achieve?
Reduces the difference between loud and soft parts of an audio signal
Increases the sampling rate of the audio
Adds reverberation to the recording
Converts mono audio to stereo
Explanation - Compression attenuates high‑level signals and/or amplifies low‑level signals, making the overall volume more uniform.
Correct answer is: Reduces the difference between loud and soft parts of an audio signal
Q.59 Which signal processing method is used in smartphones to improve voice clarity by reducing background noise?
Beamforming with multiple microphones
FFT‑based frequency shifting
Amplitude modulation
Time‑division multiplexing
Explanation - By steering the microphone array's sensitivity toward the speaker and suppressing other directions, beamforming enhances speech while reducing ambient noise.
Correct answer is: Beamforming with multiple microphones
Q.60 What is the main purpose of applying a 'high‑pass filter' to an ECG signal before QRS detection?
To remove low‑frequency baseline wander
To increase the amplitude of the QRS complex
To convert the signal to the frequency domain
To compress the data
Explanation - Baseline wander can obscure the QRS morphology; a high‑pass filter attenuates frequencies below ~0.5 Hz, improving detection reliability.
Correct answer is: To remove low‑frequency baseline wander
Q.61 In a communication system employing CDMA, what is the role of the 'spreading code'?
To increase the data rate by multiplexing symbols
To spread the signal bandwidth, allowing multiple users to share the same frequency spectrum
To compress the transmitted data
To encrypt the message
Explanation - Each user is assigned a unique pseudo‑random code that spreads the signal; receivers despread using the same code to retrieve the intended data.
Correct answer is: To spread the signal bandwidth, allowing multiple users to share the same frequency spectrum
Q.62 Which of the following is a typical application of the 'short‑time Fourier transform' (STFT)?
Analyzing non‑stationary signals like speech or music
Designing analog filters
Generating random noise
Encoding video frames
Explanation - STFT divides a signal into short, overlapping windows and computes the FFT of each, revealing how frequency content evolves over time.
Correct answer is: Analyzing non‑stationary signals like speech or music
Q.63 What does the term 'aliasing' refer to in the context of digital signal sampling?
Loss of amplitude information due to quantization
Distortion caused by insufficient sampling rate leading to frequency folding
Increase in signal-to-noise ratio
Improved resolution of the spectrum
Explanation - When sampling below the Nyquist rate, higher frequency components fold back into lower frequencies, corrupting the spectrum.
Correct answer is: Distortion caused by insufficient sampling rate leading to frequency folding
Q.64 In image processing, which technique is commonly used to improve contrast by spreading out the most frequent intensity values?
Histogram equalization
Median filtering
Fourier transform
Edge detection
Explanation - Histogram equalization redistributes pixel intensities to utilize the full dynamic range, enhancing contrast.
Correct answer is: Histogram equalization
Q.65 Which of the following best describes a 'spectrum analyzer'?
A device that measures the amplitude of a signal versus frequency
A tool that compresses audio signals
A circuit that generates random noise
A filter that removes low frequencies
Explanation - Spectrum analyzers display the power or magnitude of frequency components, helping engineers assess signal characteristics.
Correct answer is: A device that measures the amplitude of a signal versus frequency
Q.66 In which application would you typically use a 'chirp' signal?
Radar range measurement
Audio compression
Image sharpening
Digital encryption
Explanation - A chirp (frequency‑modulated pulse) provides good range resolution and processing gain in radar and sonar systems.
Correct answer is: Radar range measurement
Q.67 What is the purpose of 'error‑correcting codes' (ECC) in digital communication?
To increase the transmission power
To detect and correct errors introduced by the channel
To compress the data stream
To shift the carrier frequency
Explanation - ECC adds redundancy to the transmitted data, enabling the receiver to identify and fix bit errors without retransmission.
Correct answer is: To detect and correct errors introduced by the channel
Q.68 Which of the following is a primary function of a 'digital up‑converter' (DUC) in a transmitter chain?
To convert baseband samples to a higher intermediate frequency for transmission
To filter out noise from the received signal
To decode received data bits
To compress the transmitted waveform
Explanation - A DUC mixes baseband signals with a carrier, filters, and interpolates to the desired RF frequency before amplification.
Correct answer is: To convert baseband samples to a higher intermediate frequency for transmission
Q.69 In audio processing, which effect simulates the sound of a small, enclosed space like a cabinet?
Reverb
Chorus
Flanger
Guitar amp modeling
Explanation - Amp modeling uses DSP to emulate the frequency response and non‑linear behavior of specific amplifiers and cabinets.
Correct answer is: Guitar amp modeling
Q.70 What does the term 'bit depth' specify in digital audio?
The number of samples taken per second
The number of bits used to represent each audio sample
The frequency range of human hearing
The amount of compression applied
Explanation - Bit depth determines the dynamic range and quantization noise level; common values are 16‑bit (CD) and 24‑bit (studio).
Correct answer is: The number of bits used to represent each audio sample
Q.71 Which algorithm is commonly used for echo cancellation in voice over IP (VoIP) applications?
Least Mean Squares (LMS)
Fast Fourier Transform (FFT)
Huffman coding
Phase‑locked loop (PLL)
Explanation - LMS adaptive filters iteratively estimate and subtract the echo path, making them suitable for real‑time VoIP echo suppression.
Correct answer is: Least Mean Squares (LMS)
Q.72 In digital communication, what is the purpose of a 'scrambler' used before transmission over a line code such as NRZ?
To ensure a sufficient number of transitions for clock recovery
To encrypt the data
To increase the data rate
To convert analog signals to digital
Explanation - Scramblers randomize the data pattern, preventing long runs of zeros or ones that could cause loss of synchronization.
Correct answer is: To ensure a sufficient number of transitions for clock recovery
Q.73 Which of the following best characterizes 'spectral leakage' in an FFT analysis?
Loss of time resolution
Spreading of energy from a true frequency component into adjacent bins
Increase in sampling rate
Reduction of amplitude of the signal
Explanation - Spectral leakage occurs when the signal is not perfectly periodic within the observation window, causing energy to leak into neighboring frequency bins.
Correct answer is: Spreading of energy from a true frequency component into adjacent bins
Q.74 In the context of image compression, what does 'lossy' mean?
The compression algorithm loses some of the original image data permanently
The compression is reversible
The image is converted to black and white
The file size becomes larger
Explanation - Lossy compression discards less important information to achieve higher compression ratios, leading to irreversible quality loss.
Correct answer is: The compression algorithm loses some of the original image data permanently
Q.75 Which of the following techniques is employed in speech coders like AMR to reduce bit rate while preserving intelligibility?
Linear Predictive Coding (LPC)
Discrete Cosine Transform (DCT)
Wavelet packet coding
Frequency hopping
Explanation - LPC models the speech production mechanism, allowing efficient representation of the vocal tract characteristics with few parameters.
Correct answer is: Linear Predictive Coding (LPC)
Q.76 What is the main advantage of using a 'multi‑rate' system (e.g., decimation and interpolation) in DSP?
It reduces computational load by processing at lower sample rates when possible
It eliminates the need for filters
It always improves signal quality
It simplifies hardware design
Explanation - Multi‑rate techniques allow expensive processing to be performed at reduced sampling rates, saving resources while maintaining performance.
Correct answer is: It reduces computational load by processing at lower sample rates when possible
Q.77 Which of the following is a common use of the 'Discrete Wavelet Transform' (DWT) in image processing?
Edge detection
Image compression (e.g., JPEG‑2000)
Color space conversion
Histogram equalization
Explanation - DWT provides a multi‑resolution representation of images, enabling efficient compression with better quality at high compression ratios.
Correct answer is: Image compression (e.g., JPEG‑2000)
Q.78 In the context of satellite communication, what does the term 'link budget' refer to?
A financial account of the satellite's cost
A calculation of all gains and losses from transmitter to receiver to ensure adequate signal strength
The number of satellites in orbit
The data rate of the communication link
Explanation - Link budget accounts for transmitter power, antenna gains, path loss, and receiver sensitivity to predict link performance.
Correct answer is: A calculation of all gains and losses from transmitter to receiver to ensure adequate signal strength
Q.79 Which filter type is inherently stable and can provide an exact linear phase response?
IIR Butterworth filter
FIR filter
Chebyshev Type‑I filter
Elliptic filter
Explanation - FIR filters have only zeros, no poles, guaranteeing stability, and with symmetric coefficients they achieve linear phase.
Correct answer is: FIR filter
Q.80 What is the purpose of a 'carrier recovery' circuit in a digital communications receiver?
To generate the original carrier frequency for demodulation
To increase the bandwidth of the received signal
To encode the transmitted data
To compress the incoming data
Explanation - Carrier recovery extracts the phase and frequency of the transmitted carrier so that the baseband data can be correctly demodulated.
Correct answer is: To generate the original carrier frequency for demodulation
Q.81 In a digital audio effect, what does a 'phaser' do to the signal?
Adds a delayed copy of the signal with varying phase to create comb filtering
Increases the overall loudness
Compresses the dynamic range
Changes the sampling rate
Explanation - A phaser modulates the phase of an all‑pass filter, producing moving notches in the frequency spectrum that sound like sweeping peaks.
Correct answer is: Adds a delayed copy of the signal with varying phase to create comb filtering
Q.82 Which of the following is a typical application of a 'digital filter bank' in communications?
Implementing multi‑carrier modulation schemes like OFDM
Generating analog carrier signals
Increasing the transmitted power
Encrypting the data
Explanation - Filter banks separate and process individual sub‑carriers in OFDM, allowing efficient modulation and demodulation.
Correct answer is: Implementing multi‑carrier modulation schemes like OFDM
Q.83 What does the term 'coherent detection' imply in a digital receiver?
The receiver knows the exact carrier phase and frequency for demodulation
The signal is detected without a reference carrier
Only amplitude information is used
The detection is performed after the signal is compressed
Explanation - Coherent detection uses a synchronized local oscillator to recover both amplitude and phase, enabling demodulation of complex constellations.
Correct answer is: The receiver knows the exact carrier phase and frequency for demodulation
Q.84 Which of the following best explains why 'oversampling' can improve the performance of an ADC?
It reduces quantization noise by spreading it over a wider frequency range that can be filtered out
It increases the voltage swing of the input signal
It automatically compresses the data
It eliminates the need for an anti‑aliasing filter
Explanation - Oversampling moves quantization noise out of the band of interest, allowing a digital filter to remove it and improve effective resolution.
Correct answer is: It reduces quantization noise by spreading it over a wider frequency range that can be filtered out
Q.85 In a digital communication system using QPSK, how many bits are conveyed per symbol?
1
2
3
4
Explanation - Quadrature Phase Shift Keying (QPSK) uses four distinct phase states, each representing two bits of information.
Correct answer is: 2
Q.86 Which technique is used in 'active noise cancellation' headphones to reduce ambient sound?
Generating an anti‑phase copy of the incoming noise and adding it to the audio signal
Increasing the volume of the music
Applying a low‑pass filter to the music
Using a band‑stop filter on the audio output
Explanation - ANC headphones sense external noise, invert its phase, and superimpose it onto the audio, causing destructive interference that cancels the noise.
Correct answer is: Generating an anti‑phase copy of the incoming noise and adding it to the audio signal
Q.87 What is the main advantage of using a 'digital filter' over an analog filter in modern communication systems?
Digital filters can be reprogrammed and provide precise, repeatable characteristics
Digital filters have zero latency
Analog filters are always unstable
Digital filters require no power
Explanation - Digital filters are implemented in software/hardware that can be updated, calibrated, and produce exact responses irrespective of component tolerances.
Correct answer is: Digital filters can be reprogrammed and provide precise, repeatable characteristics
Q.88 In the context of image processing, what does the term 'morphological operation' refer to?
Processing based on the shape of structures, such as dilation and erosion
Applying a Fourier transform to the image
Adjusting the image's brightness
Compressing the image using Huffman coding
Explanation - Morphological operations manipulate binary or grayscale images using structuring elements to emphasize or remove specific shapes.
Correct answer is: Processing based on the shape of structures, such as dilation and erosion
Q.89 Which of the following is a key benefit of using the 'Karhunen‑Loève Transform' (KLT) in signal compression?
It provides the most compact representation by decorrelating the data optimally
It is computationally simpler than the DCT
It always yields lossless compression
It works only for audio signals
Explanation - KLT (or PCA) diagonalizes the covariance matrix, concentrating signal energy into few coefficients, which is optimal for compression.
Correct answer is: It provides the most compact representation by decorrelating the data optimally
Q.90 What is the primary function of a 'digital integrator' in a control system implemented with DSP?
To accumulate the sum of input samples over time, providing integral action
To differentiate the input signal
To perform a fast Fourier transform
To filter out high‑frequency noise
Explanation - A digital integrator sums successive samples, implementing the integral term in PID controllers for steady‑state error elimination.
Correct answer is: To accumulate the sum of input samples over time, providing integral action
Q.91 In a digital communications context, which technique helps to mitigate inter‑symbol interference (ISI) caused by multipath fading?
Using a cyclic prefix in OFDM symbols
Increasing the carrier frequency
Applying amplitude modulation
Reducing the data rate
Explanation - The cyclic prefix provides a guard interval longer than the channel delay spread, preventing ISI between OFDM symbols.
Correct answer is: Using a cyclic prefix in OFDM symbols
Q.92 Which of the following best describes a 'spectral centroid' in audio analysis?
The center of mass of the spectrum, indicating brightness of a sound
The highest frequency present in the audio
The time at which the audio signal reaches its peak amplitude
The average amplitude of the audio signal
Explanation - Spectral centroid is computed as the weighted mean of the frequencies present, reflecting the perceived sharpness or brightness of the timbre.
Correct answer is: The center of mass of the spectrum, indicating brightness of a sound
Q.93 In which application is a 'digital down‑converter' (DDC) essential?
Receiving and processing a specific RF channel in a software‑defined radio
Generating high‑frequency carrier signals for transmission
Amplifying audio signals for a speaker
Encoding video streams for streaming
Explanation - A DDC shifts the desired RF band to baseband and reduces the sampling rate, making further digital processing feasible.
Correct answer is: Receiving and processing a specific RF channel in a software‑defined radio
Q.94 What is the primary advantage of using 'frequency hopping spread spectrum' (FHSS) in wireless communications?
Improved resistance to interference and eavesdropping
Higher data rates than OFDM
Simpler transmitter design
Reduced power consumption
Explanation - FHSS rapidly changes carrier frequency according to a pseudorandom sequence, making the signal less susceptible to narrowband interference and harder to intercept.
Correct answer is: Improved resistance to interference and eavesdropping
Q.95 Which of the following is a common method for measuring the similarity between two signals in pattern recognition?
Cross‑correlation
Fast Fourier Transform
Zero‑padding
Amplitude clipping
Explanation - Cross‑correlation evaluates the similarity as a function of lag, useful for template matching and time‑delay estimation.
Correct answer is: Cross‑correlation
Q.96 In the context of digital signal processing, what does the term 'latency' refer to?
The delay between input acquisition and output generation
The sampling rate of the system
The maximum amplitude of the signal
The number of bits used per sample
Explanation - Latency measures how long a system takes to process data, important in real‑time applications like audio and communications.
Correct answer is: The delay between input acquisition and output generation
Q.97 Which of the following is a primary reason to use a 'windowed sinc' function when designing an FIR filter?
To control the trade‑off between main‑lobe width and side‑lobe level, reducing ripple
To increase the filter's order without affecting performance
To make the filter adaptive
To convert the filter to an IIR filter
Explanation - Windowing the ideal sinc impulse response smooths the abrupt truncation, managing transition width and stop‑band attenuation.
Correct answer is: To control the trade‑off between main‑lobe width and side‑lobe level, reducing ripple
Q.98 In a digital video system, what does 'motion compensation' achieve?
Predicts and encodes only the differences between successive frames
Increases the frame rate by interpolating new frames
Applies a global color correction
Reduces the audio bitrate
Explanation - Motion compensation estimates object movement, allowing the encoder to transmit residuals rather than full frames, saving bandwidth.
Correct answer is: Predicts and encodes only the differences between successive frames
Q.99 Which of the following best describes the 'Nyquist frequency' for a sampled signal with a sampling rate of 48 kHz?
24 kHz
48 kHz
96 kHz
12 kHz
Explanation - The Nyquist frequency is half the sampling rate; for 48 kHz it is 24 kHz, representing the highest frequency that can be correctly represented.
Correct answer is: 24 kHz
Q.100 In speech processing, what is the purpose of extracting 'Mel‑frequency cepstral coefficients' (MFCCs)?
To obtain a compact representation of the short‑term power spectrum that models human auditory perception
To increase the sampling rate of the audio
To compress the speech signal losslessly
To remove background noise completely
Explanation - MFCCs map the spectrum onto the Mel scale, decorrelate the coefficients, and are widely used for speech recognition tasks.
Correct answer is: To obtain a compact representation of the short‑term power spectrum that models human auditory perception
Q.101 Which of the following is a primary application of digital signal processing in automotive safety systems?
Radar‑based collision avoidance and adaptive cruise control
Designing the car chassis
Choosing paint colors
Scheduling maintenance appointments
Explanation - DSP processes radar returns to detect obstacles, estimate distance and speed, enabling safety features like automatic braking.
Correct answer is: Radar‑based collision avoidance and adaptive cruise control
Q.102 What is the main benefit of using 'error‑concealment' techniques in video streaming over lossy networks?
To hide the visual impact of lost or corrupted packets, improving perceived quality
To increase the video resolution
To compress the video further
To encrypt the video stream
Explanation - Error‑concealment replaces missing data with approximations (e.g., motion‑compensated interpolation), reducing visible artifacts.
Correct answer is: To hide the visual impact of lost or corrupted packets, improving perceived quality
Q.103 Which transform is typically used for efficient implementation of convolution in digital filters?
Fast Fourier Transform (FFT)
Laplace Transform
Z‑Transform
Hilbert Transform
Explanation - Convolution in time domain equals multiplication in frequency domain; FFT enables fast convolution via the convolution theorem.
Correct answer is: Fast Fourier Transform (FFT)
Q.104 In the context of audio codecs, what does the term 'bitrate' indicate?
The number of bits processed per second of audio
The maximum frequency that can be reproduced
The number of audio channels
The sampling frequency of the audio
Explanation - Bitrate determines audio quality and file size; higher bitrate generally yields better fidelity.
Correct answer is: The number of bits processed per second of audio
Q.105 Which of the following is an example of a 'time‑variant' system in signal processing?
A filter whose coefficients change adaptively over time
A static low‑pass FIR filter with fixed coefficients
An ideal integrator
A perfect delay line
Explanation - If a system's parameters vary with time, its behavior depends on when the input is applied, making it time‑variant.
Correct answer is: A filter whose coefficients change adaptively over time
Q.106 Which method is commonly used to estimate the direction of arrival (DOA) of sound in microphone arrays?
Generalized Cross‑Correlation (GCC)
Fast Fourier Transform (FFT)
Discrete Cosine Transform (DCT)
Huffman coding
Explanation - GCC computes time‑difference of arrival between microphone pairs, from which the source direction can be inferred.
Correct answer is: Generalized Cross‑Correlation (GCC)
Q.107 What is the role of a 'soft‑decision' decoder in error‑correcting codes?
It uses probability information from the demodulator to improve decoding performance
It hard‑limits the received bits to 0 or 1 before decoding
It reduces the data rate
It encrypts the decoded data
Explanation - Soft‑decision decoding takes confidence levels (e.g., log‑likelihood ratios) into account, offering better error correction than hard‑decision decoding.
Correct answer is: It uses probability information from the demodulator to improve decoding performance
Q.108 In image processing, which operation is used to fill small holes inside foreground objects?
Morphological closing
Edge detection
Histogram equalization
Fourier transform
Explanation - Closing (dilation followed by erosion) expands object boundaries and then shrinks them, effectively filling narrow gaps and holes.
Correct answer is: Morphological closing
Q.109 Which of the following best describes the 'sampling theorem'?
A band‑limited signal can be perfectly reconstructed if sampled at a rate greater than twice its highest frequency component
Increasing the number of bits per sample reduces quantization noise
A signal can be compressed without loss if its bandwidth is narrow
The amplitude of a sampled signal is always less than the original
Explanation - The Nyquist‑Shannon sampling theorem defines the minimum sampling rate needed to avoid aliasing and allow exact reconstruction.
Correct answer is: A band‑limited signal can be perfectly reconstructed if sampled at a rate greater than twice its highest frequency component
Q.110 In a digital communication system, why is 'interleaving' used before error‑correcting coding?
To spread burst errors over multiple codewords, making them easier to correct
To increase the data rate
To compress the transmitted data
To convert analog signals to digital
Explanation - Interleaving rearranges the order of bits so that a burst error affects only one bit per codeword, improving the effectiveness of ECC.
Correct answer is: To spread burst errors over multiple codewords, making them easier to correct
Q.111 Which of the following is a typical application of digital signal processing in the field of seismology?
Filtering out ambient noise to detect earthquake waveforms
Generating synthetic oil reservoirs
Designing drilling equipment
Compressing seismic data for storage
Explanation - DSP techniques like band‑pass filtering and matched filtering enhance weak seismic signals, aiding in event detection.
Correct answer is: Filtering out ambient noise to detect earthquake waveforms
Q.112 What does the term 'dynamic range' refer to in audio signal processing?
The ratio between the loudest undistorted signal and the noise floor
The difference between left and right channel levels
The total duration of an audio track
The sampling frequency of the audio
Explanation - Dynamic range quantifies the usable amplitude span of an audio system, influencing perceived loudness and clarity.
Correct answer is: The ratio between the loudest undistorted signal and the noise floor