Week Three Summary of Science Lesson 2

Sound is longitudinal waves that propagate through the medium. Medium or intermediate substances can be liquid, solid or gas. Sound is move through each of those medium by vibrating the molecules in the matter.

So, for example, sound waves can propagate in water, coal and air so, the echo is a reflected wave/reaction of the emitted sound waves. 

Sound waves can not propagate in a vacuum because there is no airborne particles.

Connection between pitch and frequency

The faster the vibration of something producing sound, the higher the pitch tend to perceive that sound to be. The higher the frequency the higher the pitch. 

Connection between loudness of sound and amplitude

Loudness of sound depends on how big the vibrations are. The amplitude of a sound wave is a measure of the amount of energy in the wave. So, greater the intensity of a sound, the greater the amplitude.

Properties of sound waves

Sound waves have properties which are:

- Reflection

- Refraction

- Diffraction

Based on the limits of human hearing, sound waves are divided into:

• Audio sonic - sounds that can be heard in ordinary human ear, has a frequency of 20 Hz - 20,000 Hz.
• Infrasonic - sounds can not be heard in ordinary human ear because it has a frequency below 20 Hz. Example: dogs and elephants.
• Ultrasonic - sound can not be heard in ordinary human ear because it has a frequency more than 20,000 Hz. Example: bats and dolphins.

The speed of sound is the term used to refer to the speed of sound waves propagating in medium. the sound of wave propagation speed may vary depending on the medium that is passed (eg. sound travel faster through water than air), the properties of the medium and temperature. However, the term is more commonly used for the speed of sound in air. The speed of sound wave refers to how fast the disturbance is passed from particle to particle. Since the speed of a wave is defined as the distance that a point on a wave travels per unit of time, it often expressed in units of meters/second (m/s).

Equation for speed of sound:

V= s (distance)/ t

Next, I will discuss about a video that I watched which is, Where Music Meets Science Part 1: Pitch and Frequency.

This video talk about the frequency and pitch. Great composer write music has many pitches ranging high to low and that's keep music interesting. Many musicians choose their instruments based on the musical range of that instrument. If the instrument have high pitch then, it have high frequency and if the instrument have low pitch, it have low frequency. 
To know about the frequency of wave in the air, on the video it describe by a pebble that drops into the water. The water as the air and the pebble as the sound. The pebble get querier when the pebble getting further and further away.  A small pebble creates a higher frequency or high pitch of waves, it creates small waves that very close together. A large rock creates a lower frequency or low pitch of waves, it creates much larger wave that's require larger space to develop. Speed and the size of the wave relates that wave frequency.
One complete vibration of a wave is called cycle. The number of cycles or waves per second is the waves frequency. Another name for cycle per second its called Hertz (Hz). 

Cycle/Second= Hertz or Hz

We can conclude based on the video that sound created by the changes of air pressure, this changes occur in wave like motion. Faster wave or frequency represent high pitches and slower wave or frequency represent low pitches.