Which of the following is NOT affected by ordinary man-made noise in communication?

Microwave signals are typically more resilient to ordinary man-made noise compared to other forms of communication. This resilience comes from their operation in a frequency range that can penetrate through obstacles and is relatively less subject to interference from typical noise sources, such as electrical devices and urban environments.

Laser signals, transmitted through light, can be significantly affected by atmospheric conditions, scattering, and interference from various sources, making them more vulnerable to disruption by man-made noise. Similarly, ultrasonic waves, which operate at frequencies above the range of human hearing, can be influenced by the same types of noise as well.

Therefore, the unique properties of microwave signals, specifically their stability and ability to maintain signal integrity in noisier environments, differentiate them from laser signals and ultrasonic waves, making them less affected by ordinary man-made noise in communication.