In AM, the amplitude of the carrier signal varies in accordance with the audio signal. This means that any fluctuations or interference in the amplitude of the carrier wave can result in distortion or loss of the audio information. Noise, such as static or other electrical disturbances, can easily affect the amplitude of the carrier, causing audible noise in the received audio.
On the other hand, in FM, the frequency of the carrier wave varies in accordance with the audio signal. This means that the information is encoded in the frequency variations, rather than the amplitude. Noise and interference tend to affect the amplitude more significantly than the frequency of a signal. Therefore, FM is less susceptible to amplitude-based distortions caused by noise, making it more resistant to noise overall.
Additionally, FM has a higher signal-to-noise ratio (SNR) compared to AM, which further enhances its ability to reject noise and provide a clearer audio signal.
For these reasons, FM is the preferred modulation technique for high-quality audio broadcasting, as it ensures better reception and clarity in the presence of noise.