Wavelength connects the temporal domain (frequency) to the spatial domain (physical size), and this relationship governs virtually every aspect of acoustics. Sound interacts differently with objects depending on whether the object is large or small relative to the wavelength. When an object is much larger than the wavelength, it reflects sound efficiently and casts a shadow behind it. This is why high frequencies (short wavelength) are easily blocked by barriers and reflected by surfaces. When an object is much smaller than the wavelength, sound diffracts around it as if it were not there. This is why low frequencies (long wavelength) pass around obstacles and are difficult to block. Acoustic absorption materials must be a significant fraction of a wavelength thick to be effective. A 50mm acoustic foam panel provides meaningful absorption above approximately 1700 Hz (wavelength 200mm, panel is quarter-wavelength). Below that frequency, the foam is too thin relative to the wavelength. This is why low-frequency absorption requires thick panels, deep cavities, or membrane absorbers. Speaker coverage is also wavelength-dependent. A horn controls directivity only at frequencies where the horn mouth is larger than the wavelength. Below this frequency, the horn loses control and the speaker radiates more broadly. Room modes occur at frequencies where the room dimensions equal half-wavelength multiples. A 5-metre room has its first axial mode at 34.3 Hz (wavelength = 10 metres, half-wavelength = 5 metres). SonaVyx's RTA mode reveals these modal peaks and dips in the measured response.