Question

A male voice after modulation transmission sounds like that of a female to the receiver. The problem is due to:
A. Poor selection of modulation index
B. Poor bandwidth selection of amplifiers
C. Poor selection of carrier frequency
D. Loss of energy in transmission

Answer 1

Hint: There is a difference in the voice between male and female, even if they are at the same level of loudness, because of the variation of the quantity called pitch, which indicates the level of grave or shrill in the tone. This pitch is determined by the frequency. So, we need to understand that in this problem, the main issue is the variation in frequency.

Complete step-by-step answer:
The pitch is a property of the sound that is calibrated on a frequency-related scale. It is the quality that determines the sound to be judged as shriller or not. Pitch is a major component associated with a musical melody.
The pitch of the sound produced by male is lesser than that of females.
So, in this problem, the male voice sounds like a female, because there is a change in the frequency in the voice at the receiver as compared to the input end.
In this case, the frequency of the voice at the receiving end is higher than usual, which is a result of an error in the communication channel.
This error mainly, occurs due to improper selection of bandwidth for the sound amplifiers on the input and the receiving end.
There are two kinds of modulation:
i) Amplitude Modulation
ii) Frequency Modulation
The bandwidth in the amplitude modulation is twice as that of the frequency of the modulating signal. This should be taken care of, while selecting the bandwidth.
If the proper bandwidth is not chosen, the frequency of the receiving end varies beyond the normal and as in this case, the frequency increases and the pitch of the male voice sounds as a female voice.
Hence, the poor selection of bandwidth of the amplifiers is the main reason for this.

Hence, the correct option is Option B.

Note: The bandwidth for the Amplitude modulation and frequency modulation is given by the equations as follow:
For AM,
Bandwidth, $B = 2{f_m}$
where ${f_m}$ = modulating frequency.
For FM,
Bandwidth, $B = 2{f_m}\left( {\beta + 1} \right)$
where $\beta $ is called a modulation index, which is the ratio of deviation in frequency to the modulating frequency.