What is the purpose of de-emphasis in the receiver audio stage?

The purpose of de-emphasis in the receiver audio stage is specifically linked to its role in audio processing to achieve a flat audio response while simultaneously reducing noise. This process works in conjunction with pre-emphasis applied at the transmitter stage.

During transmission, pre-emphasis boosts high-frequency signals to combat the higher noise levels associated with those frequencies. When the signal reaches the receiver, de-emphasis is applied to revert the high-frequency response back to a more neutral state. This not only flattens the frequency response, ensuring that both high and low frequencies are reproduced equally, but it also has the beneficial effect of reducing any noise that may have been introduced during transmission, especially in the higher frequency ranges.

This method is particularly effective in FM (Frequency Modulation) systems, where pre-emphasis and de-emphasis work together to enhance overall audio quality and clarity while minimizing the impact of noise disturbances. Thus, option C accurately captures the dual objective of achieving a flat audio response while also reducing noise through this complementary process.