PhysicsChapter 4: Sound
Ultrasound and Infrasound
Introduction
Human hearing covers only a limited frequency range. For a young healthy person, the commonly quoted approximate range is: 20 Hz to 20,000 Hz
Definition
Infrasound
Sound with frequency below about 20 Hz is called **infrasound*. Humans normally cannot hear it. It can be produced by: earthquakes; volcanoes; large machines; * some animals.
Ultrasound
Sound above about 20 kHz is called **ultrasound**. Humans normally cannot hear it.
Uses of Ultrasound
* medical imaging; * sonar; * industrial flaw detection; cleaning; distance measurement.
Medical Ultrasound
High-frequency sound pulses enter the body and reflect from boundaries between different tissues. The returning echoes are processed to produce images.
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Review the key facts, formulas and checks before you move on.Ultrasound and Infrasound
Sticky Notes · Quick Revision
INFRASOUND
- <20 Hz
HUMAN RANGE
- ~20 Hz–20 kHz
ULTRASOUND
- > 20 kHz