Basic Qualification · B-005 Basic electronics and theory · B-005-007-003
Why is the range of frequencies from 20 Hz to 20 kHz termed audio frequencies?
- A Because sound can be in this range it's too low for RF signals
- B Because RF signals in this range can directly converted to sound
- C Because the human ear can sense sound in this range
- D Because this is the speaker response range of a modern SSB receiver
Correct answer: C — Because the human ear can sense sound in this range. From the official ISED question bank, verified word for word.
Why
The term audio frequencies covers 20 Hz to 20 kHz because this specific span matches the sounds the human ear can actually hear. The full explanation — and one for every question — is in Pro.
Practise this section
The theory: Ohm's law, power, series and parallel circuits, AC and DC, frequency and wavelength, decibels, and the metric prefixes the exam leans on.