The term "in-frequencies" refers to those frequencies that are uncommon or scarce, and may not be found easily. Synonyms for this term include rare frequencies, infrequent wavelengths, irregular oscillations, and sporadic vibrations. It can also be referred to as low frequency, as it is often found in the lower end of the electromagnetic spectrum. In-frequencies may occur in various contexts, such as in communication channels, sound waves, or even in natural phenomena such as earthquakes. Whatever the context, the use of synonyms for this term can help to communicate its meaning more effectively, allowing for better understanding of the topic at hand.