What is one way that voice is transmitted in a pulse-width modulation system?

Pulse-width modulation (PWM) is a technique used to encode information in a digital signal through the variation of the width of the pulses. In the context of voice transmission, the key characteristic of PWM is that the duration of each pulse is adjusted in accordance with the amplitude of the voice signal at a given moment. This means that when the voice waveform has a higher amplitude, the pulse duration is wider, and when the amplitude is lower, the pulse duration is narrower.

This method effectively captures the nuances of the voice signal, allowing the modulation to represent the original audio more accurately. By encoding voice information in this manner, the system can transmit rich audio details while maintaining the clarity needed for effective communication.

The other options do not accurately describe PWM. Variations in frequency or amplitude do not pertain to pulse-width modulation, as they suggest different modulation techniques such as frequency modulation (FM) or amplitude modulation (AM). The notion of a fixed duration for a pulse would negate the fundamental principle of PWM, which revolves around changing the pulse widths to convey information.