Ääniaalot

Ääniaalot are mechanical waves that transport sound energy through a medium by alternating regions of compression and rarefaction. They require matter to propagate and cannot travel in a vacuum. In fluids such as air and water, sound waves are primarily longitudinal. In solids, both longitudinal and transverse waves can exist, and surface waves may occur along boundaries.

Key properties include frequency (f), set by the source; wavelength (λ) and speed (v) are related by v = fλ. The amplitude describes the strength of the oscillation and relates to perceived loudness. Wave speed depends on the medium and conditions, such as temperature. In air at 20°C, v ≈ 343 m/s; in water ≈ 1480 m/s; in steel ≈ 5000 m/s.

Attenuation reduces amplitude as the wave travels, through absorption (conversion to heat), scattering, and geometric spreading.

Humans hear roughly 20 Hz to 20 kHz. Sound intensity is measured in decibels, referencing a standard threshold of hearing. The same frequency can be perceived differently depending on the environment and medium.

Applications and phenomena associated with Ääniaalot include acoustics and music, communication and voice transmission, sonar and echolocation, and medical ultrasound and nondestructive testing. The study of these waves encompasses wave behavior such as reflection, refraction, diffraction, and interference, as well as how medium properties and boundaries shape how sound propagates and is perceived.