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# Sound properties: amplitude, period, frequency, wavelength

How to find the amplitude, period, frequency, and wavelength for a sound wave. Created by David SantoPietro.

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• I understand that amplitude determines volume and frequency determines pitch. What changes the quality of a sound? For example, an oboe, a violin, and the speaker in this video can all produce a sustained 440 hz A at the same volume. Why do they sound different?
• Good question.
I think firstly it is to do with the shape of the wave. This will be determined by the features of the instrument (eg a violin tends to be triangluar shape I believe,)
As well as the physics, I expect there will also be stuff going on inside your brain that 'interprets' or evens adds to the sound depending on what other senses pick up....for example if you see an oboe, it can effect the quality of the sound experienced. Obviously things like echo or resonance will also have an impact on quality.

MMm sory its a bit vague but hope it helps ...
• In the displacement vs position graph, what do we mean by position? Where is time? Is this not just position through time, which is basically displacement, which is the y axis, is time not the x axis?

Furthermore, it seems that in the displacement vs position graph, it seems that we are tracking the horizontal motion of a particle and graphing it's distance over time in the vertical direction, at , this is the exact same thing, the particle goes right, the line of the graph goes up, it's even rotated and shown horizontally to reflect this, so there seems to be no difference, as the y and x axis seems to represent the same information, and the same type of information seems to be graphed.
• No, That graph is like a picture showing where MANY particles were at ONE specific moment in time. the x axis represents the "equilibrium location" of the medium's particles. It may be measured as the distance between the particles and the sound source or some given point. In effect this graph is saying, that at this point in time, the particles whose equilibrium is x meters from the source had moved y meters from their equilibrium.
• why cant we hear sound with frequency above 20 000 Hz
• We really just aren't made to. In order to hear a sound our eardrum must vibrate, and 20000 times per second is just too darn fast for it - the energy is dissipated through the bones and softer tissues around it which act as a damper. For more insight on this, look up "natural frequency" and see if you can connect the dots.
• if period increases does wavelenght increase with it ? or does it stay the same ?
• If the velocity is the same, Then by rearranging V=(wavelength or lambda) / T (time period)
Then, an increase in wavelength MUST cause a decrease in Time period & wise versa.
• What was the name of the device that was hooked to the speaker in order to get the visualization of soundwaves?
• How can we get visual representation of sound waves using an oscilloscope ?
• By using a microphone you can convert the sound waves to an electrical signal and that can be displayed on an oscilloscope.
• Is there a difference between amplitude as described in :47 (which is on the displacement vs time graph) and the green arrows at (on the displacement vs 'position x' graph)?
• how does amplitude affect the sound?