Sound waves

• The speed of sound is the distance travelled by a wave divided by the time taken.
• Sound travels faster through solids than liquids or gases.
• in the ear sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound
• ultrasound waves have a frequency higher than the upper limit of hearing for humans, so they cannot be heard.
• seismic waves are produced by earthquakes
• P-waves are longitudinal seismic waves. They travel faster in water than in rock.
• S-waves are transverse seismic waves. S-waves cannot travel through a liquid.
• Echo sounding uses high frequency sound waves to detect objects in deep water and measure water depth
• The conversion of sound waves to vibrations in solids works over a limited frequency range. This limits the range of human hearing (20Hz to 20kHz)
• Ultrasound waves are partially reflected when they meet a boundary between two different media. The time taken for the wave to reach a detector can be used to determine how far away the object is.
• In echolocation, animals emit sounds that bounce off nearby surfaces and return to their ears as echoes. These echoes contain information about the location and nature of obstacles in the environment.
• ultrasound can be used in medical imaging for pre-natal screening for pregnant women.
• The reason ultrasound is used for imaging of unborn babies is that it is safe to use whereas x-ray imaging would not be safe.