Question

What are the two main properties of a sound?

Answer 1

Sound waves travel in the form of compressions and rarefactions of small volume elements of the medium. Sound has certain distinctive properties, for the way sound energy travels in waves. Properties of sound are speed, loudness, and pitch.

Complete answer:
Sound is a longitudinal wave which makes it possible for us to hear. Sound waves are usually considered as plane sinusoidal waves, which are specified by some certain properties such as frequency, amplitude, speed and direction.
Amplitude of any wave tells us about the amount of energy it has. It is the distance of maximum vertical displacement of the wave from its equilibrium position. Amplitude of a sound wave is related to its loudness. The louder the sound means more energy.
Frequency of a wave is the rate of vibrations travelling through the medium. In terms of sound wave, frequency is related to pitch of the sound. Frequency of sound waves decide whether a sound is perceived is high pitched or low pitched. More frequency means high pitch sound and lower frequency means low pitched sound.
The speed of sound is the distance travelled by sound waves in a time period. Sound waves travel with a speed much lower than the speed of light.

Note:
Loudness of sound is measured in decibel. It is a unit of intensity in sound waves. Noise above 70 dB in longer term may damage your hearing. Loud noise above 120 dB can cause immediate harm to your ears. The frequency of sound waves is its pitch.