Sunday, April 26, 2009

Wave Interference
Definition: phenomenon which occurs when two waves meet while travelling along the same medium
There are mainly two types of wave interference: constructive and destructive
Constructive
When two waves which both have the same displacement direction, they will create a stronger wave with a higher intensity. So in layman’s term: When two waves that are travelling along a line and both are curved in a “u” or “n” shape meets each other, they will form a bigger wave. The most important requirement is that both waves have the same displacement direction. o.O
Here’s a couple illustrations taken from the website: http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l3c.html to depict what have been explained earlier.

As seen down here, two waves (represented by red and blue) of the same displacement direction (i.e. both are curved in an ‘n’ shape) meet each other to form a stronger wave (represented by green wave)
Destructive
So the opposite of constructive interference is destructive interference. As the name suggest, the waves destroy each other when they meet, hence cancelling each other out and no sound is heard.
This is also known as the creation of dead spots, which are basically places where no sound can be heard.
Destructive interference occurs when two interfering waves of different displacement direction meet each other, which will result in cancellation.
Ok, sounds cheem, but here’s another picture to help! ^^

So as seen in the two illustrations, two waves of opposite displacement direction (represented by red and blue again) meet each other and result in the cancellation, as seen by the green line.
However, destructive interference does not mean total destruction of the sound waves. As mentioned earlier, the result of destructive interference is cancellation. To be more precise it means that the affect of one of the pulses on the displacement of a given particle of the medium is destroyed or canceled by the affect of the other pulse when the two pulses overlapped each other, as quoted from the same website http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l3c.html
Superposition
We are currently still struggling to understand the concept of superposition. All that our group can understand now is that superposition is somehow applied to find the shape of the resultant wave during interference.
Anyway in our case, it would be more logical to place the sofa where the audience will be sitting at the point where there is constructive interference. However the problem is how do we determine the point where there is constructive interference? We may probably search more on the website or ask the lab technician one of these days.
Here’s a picture featuring our solution on the location of the audience.

So as seen in this picture, it would be best if we can position the seat at point A or B, which is experiencing constructive interference. The other points are suffering from destructive interference. In the picture, intersecting points between waves of different thickness means destructive interference while intersecting points between waves of equal thickness means constructive interference.
Ok, so now let’s move on to diffraction.
Diffraction
Definition: Diffraction basically refers to the phenomena experienced when a wave encounters an obstacle
Factors affecting diffraction
Wavelength – we will not be able to change the wavelength in this case, even though it may affect diffraction
Size of the Slit – Since we are trying to put as little obstacles between the speaker and the audience, diffraction doesn’t come in handy. However, it is essential when it comes to the sealing of the studio. Sound may come in from the outside of the room and diffracts when passing through any hole in the wall which may cause dramatic effects.
So, another point of our solution is that we have to seal off whatever possible slits that may be present in the wall.





here is the updated mindmap:

Posted by rainbowskies at 2:44 AM

Wednesday, April 22, 2009

Rough Plan

so we will be presenting our rough proposal:
1.we will be putting out stereo speakers at the 4 corners so as to maximize the distance away from the walls so as to create the best reverberation.
2. we will also place them off the ground on the walls.
3.furniture will be placed out of the way of the stereo system and not place any carpets or fuzzy materials to muffle the sound.
this is our basic requirements, we will be elaborating more on this later.

Posted by rainbowskies at 6:15 AM

Wednesday, April 15, 2009

updates on progress

after some weeks, we have finally done the below stated:
1.Read up and research on the different properties of sound relating to our project, namely:
I. reverberation
II. echo
III. interference
2. Do up another mindmap showing our thinking process:

we are planning to:
design the first draft for our project.

Posted by rainbowskies at 3:53 AM

Wednesday, April 1, 2009

M3 PBL

ok...so now we will be talking more about our PBL research problem.
Basically the scenario given is:
We are to set up Dr Physics’ home entertainment studio which includes furniture such as sofa and coffee table as well as a stereo sound system. In our proposal, we must acquire the correct dimension of the whole room as well as the arrangement of the furniture and the stereo system such that it does not distort the sound or compromise its quality.

So the problem is:
1.How can we arrange the furniture and the stereo system to optimize the quality of the sound system taking into consideration all the different factors?
2.How does the quality of the stereo system change if the furniture all placed differently?
3.what are the properties of sound?
4.what is the best dimension and shape of the room which will optimize the sound effect?
this is our mindmap:

Posted by rainbowskies at 3:09 AM