Standing Wave
A wave pattern that appears stationary, created when waves reflect and interfere with themselves.
A standing wave forms when a sound wave reflects off a surface and interferes with the incoming wave. At certain frequencies (room modes), this interference creates a stable pattern of nodes (minimum pressure) and antinodes (maximum pressure) that appear to stand still rather than travel.
In room acoustics, standing waves are responsible for: • Bass buildup at walls and corners (pressure maxima occur at boundaries) • Dead spots where bass nearly cancels (pressure minima) • The uneven low-frequency response that plagues small rooms
The term "standing wave" is often used interchangeably with "room mode," though technically a standing wave is the physical phenomenon while a room mode is the specific frequency at which it occurs.
Standing waves are most problematic at low frequencies where wavelengths are long enough to fit between room surfaces. A 50 Hz wave has a wavelength of about 7 meters.
Practical Example
Playing a 50 Hz tone in a room
Wavelength = 343 / 50 = 6.86 metersIf the room is ~3.4m (half wavelength), the 50 Hz tone will form a standing wave with maximum pressure at both walls and minimum pressure at the center.
Related Terms
Room Modes · Axial Mode · Wavelength
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