Units used to measure loudness are Sone (loudness N) and Phon (loudness level L). Scroll down to related links and look at "Loudness - Wikipedia" and "Sound level change and the change of the respective factor of volume and loudness"
frequency
longitudinal waves
amplitude
Surface Waves
a wave with long wavelength and high frequency.
sound waves require a medium to transfer energy
FOR A+ USERS THE ANSWER IS Sound waves travel in all directions
sound waves require a medium to transfer energy
-- They are longitudinal waves and material medium is required for their propagation.
Refraction is caused by light crossing from one medium to another.
When two or more waves occupy the same space at the same time, an interference pattern is created.
most of the EM spectrum is visible light.
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Surface waves