PHY 8 Sound Flashcards
What are sound waves ?
Longitudinal waves which can only be transmitted in a material, elastic medium.
What is the impact of a Vacuum on sound ?
Sound is produced by vibrating matter, there is no matter in a vacuum and therefore no sound.
What are compressions in terms of sound ?
They are also known as condensations - they are regions where particles of matter are close together.
What are rarefactions ?
Regions where particles are sparse. They are low pressure regions of sound waves.
What is the relative velocity of sound in solids, liquids and gases ?
Solids > Liquids > Gases
How does temperature affect the velocity of sound ?
Increase in temperature increases the velocity of sound.
What are frequencies below 20 Hz known as ?
Infrasonic
What are frequencies above 20 000 Hz known as ?
Ultrasonic
What is the sound frequency (pitch) that can be percieved by the ear ?
20 - 20 000 Hz
What are the SI units of Hertz ?
Cycles/Second = S-1
What is sound intensity ?
The rate of energy (power) propagation through space
intensity (I) = Power/Area = F2 x A2
F= Frequency, A = Amplitude
Describe a noise that could be heard at 160 DB ?
An aeroplane engine
Describe a sound that could be heard at 20 DB ?
A whisper
What are beats in terms of sound?
When sounds of different frequencies are heard together, they interfere. Constructive interference results in beats.
