devarshi-dt-logo

Question:

An audio signal consists of two distinct sounds: one a human speech signal in the frequency band of 200Hz to 2700Hz, while the other is a high-frequency music signal in the frequency band of 10200Hz to 15200Hz. The ratio of the AM signal bandwidth required to send both signals together to the AM signal bandwidth required to send just the human speech signal is:

2

5

6

3

Solution:

Bandwidth of the human speech signal without modulation, fh = 2700 - 200 = 2500 Hz
Bandwidth of the music signal without modulation, fm = 15200 - 10200 = 5000 Hz
AM signal bandwidth to send human speech signal only, Bh = 2fh = 5000 Hz
AM signal bandwidth to send both the human signal and the music signal is, Bm = 2(fm + fh) = 2(5000 + 2500) = 15000 Hz
Bm : Bh = 15000 : 5000 = 3 : 1