loud

Loud is an adjective describing sounds with high intensity, or more generally, sounds that are easily heard or attention-grabbing. In everyday speech, a loud sound is one that stands out from its surroundings due to its amplitude, spectral content, or suddenness. The word can also describe environments or events that produce such sounds.

Physically, sound level is quantified by sound pressure level, measured in decibels (dB). The human ear perceives loudness nonlinearly, and is most sensitive around 2–5 kHz. A-weighted measurements (dB(A)) adjust for this sensitivity and are commonly used in safety standards. The scale is logarithmic: a 10 dB increase is roughly perceived as twice as loud, though context matters. Thresholds of hearing are around 0 dB SPL, while typical speech is about 60–70 dB, and pain can occur near 120–130 dB SPL.

Loudness is a psychoacoustic quantity, distinct from sound pressure. It is influenced by duration, spectral content, masking by background noise, and listener factors. The phon scale expresses loudness level across frequencies relative to a reference tone, and the sone scale provides a roughly linear measure of perceived loudness.

In practical applications, managing loudness is important in music production, broadcasting, architecture, and occupational safety. Engineers shape loudness for clarity and comfort, and safety guidelines limit exposure to loud sounds to protect hearing health.