What type of noise appears as random spikes across a return path frequency spectrum?

Impulse noise is characterized by sudden, high-amplitude disturbances that manifest as random spikes in a return path frequency spectrum. This type of noise is often caused by external factors such as lightning strikes, electrical surges, or the switching of motors, which produce brief but powerful signals. These spikes can significantly disrupt communication systems, making it difficult to discern the intended signals from the noise.

White noise, on the other hand, is a type of noise that contains equal power across all frequencies, creating a consistent and pervasive sound rather than discrete spikes. Thermal noise, resulting from the random motion of electrons in a conductor, also does not exhibit the sudden, distinct spikes associated with impulse noise and instead has a more continuous nature. Signal noise typically refers to any form of interference that affects the clarity of transmitted signals, but it does not specifically denote the sudden spikes characteristic of impulse noise. Thus, impulse noise distinctly fits the description of random spikes across a frequency spectrum, confirming it as the correct choice.