Question

Frequency range for speech signals is
(A) $300\,\,Hz$ to $3100\,\,Hz$
(B) $300\,\,Hz$ to $3100\,\,MHz$
(C) $300\,\,KHz$ to $3100\,\,MHz$
(D) none of these.

Answer 1

Hint The number of waves that pass through a fixed point in a unit time; as well as the number of cycles or vibrations encountered during one unit of time by a body in a periodic motion is referred to as the frequency.

Complete step by step solution
In wireless transmission, the functional speech frequency band ranges from more or less from $300\,\,Hz$ to $3400\,\,Hz$. It is for this reason that the ultra-low frequency band of the electromagnetic spectrum between $300\,\,Hz$ and $3000\,\,Hz$ is also referred to as speech frequency, being the electromagnetic energy that denotes the audible energy at baseband. The bandwidth assigned for a single speech-frequency communication channel is generally $4\,\,Hz$, including guard bands, permitting a representation rate of $8\,\,Hz$ to be used as the basis of the pulse code modulation system used for the digital Public Switched Telephone Service.
The speech signal doesn’t have much information to carry. So, their frequency range is low, from $300\,\,Hz$ to $3100\,\,Hz$.
 Therefore, the frequency range for speech signals $300\,\,Hz$ to $3100\,\,Hz$.

Hence the option (A) $300\,\,Hz$ to $3100\,\,Hz$ is the correct answer.

Note Low Frequency or LF which sometimes called as longwave refers to Radio Frequencies in the range of $30\,\,Hz - 300\,\,Hz$. In Europe, part of the LF spectrum is used for AM broadcast service. In the western hemisphere, its main use is for aircraft beacon, navigation, information, and weather systems.