#wave propagation

• Anacoustics — A specialized branch or area of study within modern physics and sound engineering dealing with the analysis of the absolute absence of sound or the propagation of elastic waves in extremely low-density media (such as vacuums or upper atmospheric layers), where the transmission of acoustic waves becomes structurally impossible due to the lack of a fluid molecular medium.
• Antifeding — An orthographic variant or secondary graphic fluctuation in Romanian for the technical term 'antifading'; a property or circuit capable of compensating for radio signal intensity fluctuations. Although modern standards recommend 'antifading', the form with 'e' survives in older engineering papers.