Sound
por GAN MINGHAO
1. How is sound produced?
1.1. Sound waves is produced by vibrating objects
2. Audible Frequencies
2.1. 20Hz-20kHz(audible frequencies)
2.2. Ultrasound: Sounds above the upper hearing limit
2.3. Infrasound: Sounds below the lower hearing limit.
2.4. Echolocation:the sonarlike system used by dolphins,etc to detect objects by emitting usually high-pitched sounds that reflect off the object and return to the animal's ears or other sensory receptors.
3. Pitch and Frequency
3.1. Pitch:Property which distinguishes sounds.
3.1.1. pitch of a note depends on its frequency.
3.1.1.1. the higher the frequency the higher the pitch
4. Ultrasound
4.1. Sound with frequency above 20kHz
4.2. Sonar: Technique of using ultrasound to locate underwater objects.
4.3. Used to clean small,intricate items such as jewelry,spectacles,etc.
4.4. used in quality control and continuous monitoring during manufacturing process.
5. Definition
5.1. Energy propogated from one point to another as a wave.(longitudinal wave)
6. Propagation of Sound
6.1. vibrating objects alternately pushes and pulls on the air adjacent to it.
6.1.1. Compression
6.1.1.1. Layers of air pushed close together.
6.1.2. Rarefaction
6.1.2.1. the air layers pulled together.
7. Transmission of Sound through a medium
7.1. sound waves need a medium for transmission.Cannot propagate through a vacuum.
7.1.1. Solid
7.1.1.1. Fastest,because it is the densest.
7.1.2. Liquid
7.1.2.1. faster than in gas, because it is denser than gas.
7.1.3. Gas
7.1.3.1. Slowest, less dense compared to solid or liquid.
7.2. the speed of sound depends on the differences in the strength of the inter-atomic forces and closeness of the atoms in the three states.( The denser the medium the faster sound travels)
8. Speed of sound
8.1. Distance/ Time Taken
9. Echo
9.1. when the reflected sound is heard as a separate sound after an interval of silence
9.1.1. v=2d/t