What type of interference can be attributed to unwanted signals heard in addition to desired signals?

Cross-modulation interference occurs when unwanted signals are inadvertently mixed with desired signals, leading to the unwanted sounds or distortions alongside the intended audio or communication. This type of interference commonly arises when multiple signals are transmitted in the same waveband, and non-linearities in the receiving equipment create additional frequencies that carry the unwanted information. As a result, operators may hear not only the desired transmission but also other signal components that interfere with the clarity and quality of the intended communication.

Harmonic distortion refers to the unwanted harmonics generated by non-linear devices, which usually affects the fidelity of the audio signal but does not involve the mixing of different signals. Phase distortion involves changes in the phase relationship of signals, impacting the timing of frequencies but not necessarily introducing additional unwanted signals. Signal clipping occurs when the signal level exceeds the maximum capacity of the system, resulting in distortion, but it is not the same as mixing unwanted signals. Thus, in the context of this question, cross-modulation interference accurately describes the phenomenon of unwanted signals appearing alongside desired transmissions.