# Wireless & Mobile Communications Questions & Answers – Frequency Domain Coding of Speech

This set of Wireless & Mobile Communications Multiple Choice Questions & Answers focuses on “Frequency Domain Coding of Speech”.

1. Frequency domain coders divides the speech signal into __________
a) A set of frequency components
b) A set of different amplitudes
c) A set of time delays
d) A set of phase components

Explanation: In the class of frequency domain coders, the speech signal is divided into a set of frequency components. Each frequency component is quantized and encoded separately.

2. In frequency domain coding of speech, the number of bits used to encode each frequency component is constant.
a) True
b) False

Explanation: Frequency domain coders have an advantage that number of bits used to encode each frequency component can be dynamically varied. They can also be shared among different bands.

3. Quantization is a ________ process.
a) Linear
b) Direct
c) Non-linear
d) Indirect

Explanation: Quantization is a non-linear process. It produces distortion products that are typically broad in spectrum.

4. Sub band coding codes the short time transform of a windowed signal.
a) True
b) False

Explanation: It is function of block transform coding. However, a sub band coder divides the speech signal into many smaller sub bands and encodes each sub band separately according to some perceptual criterion.

5. Which of the following is one of the most frequently used transform in speech coding?
a) Fourier transform
b) Wavelet transform
c) Shearlet transform
d) Discrete cosine transform

Explanation: DCT (discrete cosine transform) is one of the most attractive and frequently used transforms for speech coding. Fast algorithms developed for computing the DCT in a computationally efficient manner are used.

6. What does ATC stands for in speech coders?
a) Automatic transform code
b) Air traffic controller
c) Active thermal convection

Explanation: In speech coding, ATC stands for adaptive transform coding. It is form of frequency domain coder that encodes the speech at bit rates in the range of 9.6 kbps and 20 kbps.

7. Waveform coders and Vocoders are the types of ____________
a) Speech coders
b) Modulation technique
c) Frequency translation methods
d) Channel allocation for transmission

Explanation: Speech coders can be classified into waveform coders and Vocoders. Waveform coders convert the analog signal into digital signal. Vocoders exploit the special properties of speech signal to reduce the bit rate.

8. The type of frequency domain coding that divides the speech signal into sub bands is _____
a) Waveform coding
b) Vocoders
c) Block transform coding
d) Sub-band coding

Explanation: Sub band coding (SBC) is a method where the speech signal is subdivided into several frequency bands and each band is digitally encoded separately. The audible frequency spectrum 20Hz-20 KHz is divided into frequency sub-bands using a bank of finite impulse response (FIR) filter and output of each filter is sampled and encoded.

9. Speech coders are categorized on the basis of __________
a) Signal compression techniques
b) Frequency of signal
c) Bandwidth of the signal
d) Phase of the signal

Explanation: Speech coders are categorised on the basis of signal compression techniques. Speech coding is an art of compressing and then encoding speech signals.

10. The speech coding technique that is dependent on the prior knowledge of the signal is __________
a) Waveform coders
b) Vocoders
c) Sub band coding
d) Block transform

Explanation: Vocoders are dependent on the prior knowledge of the signals. They capture the characteristic elements of audio signal and then uses this characteristic signal to affect other audio signals.

Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.

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