Questions to sound waves and the amplitudes - The right answers
 
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Question a): As a simple representation of a sound wave, a water wave is given.
a) In the figure, the amplitude
a has to be drawn.
 
Wasserwelle Frage
 
Question b): What are two important sound field parameters shown usually by the amplitude?

Regenbogenlinie

The correct answer to question a): The amplitude a is based on the neutral zero line.
 
Wasserwelle Antwort
 
The correct answer to question b): The sound amplitude shows the sound pressure variations Δ p in Pa or N/m² and the displacement of the air particles ξ (xi) in m.
 
See the excellent explanation:

"Soundfield Quantities of a Plane Wave − The sound amplitudes": http://www.sengpielaudio.com/SoundfieldQuantitiesPlaneWaveAmplitude.pdf
 
Note:
There is only a small general knowledge of the word amplitude in acoustics and audio engineering. Some claim that there is only one amplitude for the sound - just the "sound amplitude" or "noise amplitude". So what exactly is a sound amplitude?

 
As sound field quantity we know, the sound amplitude as the amplitude of the particle displacement (air particles), the sound pressure amplitude, the amplitude of sound particle velocity and the amplitude as pressure gradient.
 
Additional links:
"What is amplitude?"
http://www.sengpielaudio.com/calculator-amplitude.htm
 
Relationship of acoustic quantities − plane progressive acoustic sound wave http://www.sengpielaudio.com/RelationshipsOfAcousticQuantities.pdf
Relationship of sound field quantities − ξ, v, a and p (German) http://www.sengpielaudio.com/ZusammenhangDerSchallfeldgroessen.pdf
The Formula Wheel - Formulas of Acoustics (Audio)
http://www.sengpielaudio.com/FormulaWheel-Acoustics.htm
 
Discussion in the forum "tonthemen.de" − "Test questions for students about the amplitude of sound waves" with typical wrong answers (German):
http://www.tonthemen.de/viewtopic.php?f=1&t=2174&p=17406#p17406
 

Regenbogenlinie

 
http://tsunamiacs.blogspot.de/2008/06/hydrophone-tsunami-earthquake-marine.html
http://tsunamiacs.blogspot.de/
 
By Charlotte Lim, Jinny Pang, Fiona Tan, Soh Weiqing [Class 304] 25 May 2008
 
Tsunamis are obviously waves and as such they follow the fundamentals of waves. These basics are as follows:

 
Tsunami Welle Amplitude Wellenlaenge
 
This above picture shows the amplitude not correctly. Shown is the wave height.
Wave height is not amplitude. Wrong is the following text: The amplitude is the distance from the bottom of the trough to the top of the crest.
 
The amplitude, a, of a wave is the distance from the centre line, or the still position, to the top of a crest or to the bottom of a trough. Be careful with this quantity, because the centre line is not always given, like here.

 
http://ffden-2.phys.uaf.edu/212_spring2005.web.dir/Justin_Priest/wavelength.png
http://ffden-2.phys.uaf.edu/212_spring2005.web.dir/justin_priest/Tsunami%20Physics.htm
 
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