(a) Infrasound has frequencies less than 20 Hz. Examples: Bats, Dolphins, can emit ultrasound waves
(b) Ultrasound has frequencies more than 20,000 Hz. Examples: Dogs, Children below 5 years of age can hear infrasound.
- Infrasound is defined as sound oscillating from 1 to 20 times per second. Several noise sources are encountered naturally (large sea waves, wind, thunder, earthquake, volcanic eruption, etc.) or artificially (usually related to industrialization: rotating machines, punching machines, transportation, or explosions) are sources of infrasound.
- Ultrasound, just as infrasound, includes frequencies that are inaudible to humans. Various industrial applications include infrasound (cutting, welding, cleaning, machining detection)