1. Sound travel
Sound can travel through solid, liquid and gas. The media that sound can travel fastest is solid. This happened because the distance between the molecules of solid are close one each other, so the energy needed to transfer is maximum. The speed of sound in solid like steel can reach 5000 m/s. While the second media is liquid, where the molecules are closely packed one each other. Sound can travel in water with 1500 m/s. In gas, like air sound can travel 330 meter every second.
There are 3 requirements where we can hear sound that is produced, they are :
1. Vibrations. Sound is produced by vibration. Vibration in the back and forth movement by its normal position (equilibrium position).
2. Media. Media is needed by sound to transfer its energy. Light does not need media to transfer. The media can be solid, liquid and gas.
3. Receiver. Ear is used to receive signal or frequency that sound produce. The frequency must be 20hz -20khz for human to hear. If below than that it is infrasonic where dog or cat can hear, and ultrasonic where larger than 20khz where animals like dolphin or whale and shark can detect the sound.
2. Loudness and Pitch
Loudness and pitch are two different terms that very often found in musical shows. We can difference them. Loudness is talking about amplitude, you can larger or decrease the loudness of vibration by decreasing the amplitude or decreasing the force that cause the object to vibrate. While pitch is about frequency. This is the sound color. You can change the pitch by changing frequency which means that by changing the wavelength of the sound wave. Loudness is measured in decibel. decibel is the unit of loudness. The theshold where the human can hear to prevent hearing damage is 90 dB. Baby cying, aeroplane, motorbike can cause damage of human hearing. Thats whya we should close our ear if near those souce of vibrations.
