Sunday, May 17, 2009

MINDMAP


this is the new mindmap:

Posted by rainbowskies at 6:51 AM

Final PBL report

Dear Everyone:
this is our final PBL report and possibly the last post on this blog. it has been a great time doing this project. enjoy:

1. Problem Statement:
The problem is to set up a home entertainment studio, which includes furniture such as sofa and coffee table as well as a stereo sound system such that the sound quality can be maximized.
2. Background research:
Relevant information and concepts which are/can be put into use:
• Echo
• Reverberation
• Diffraction
• Interference
• Superposition

Echo: Echo is basically the reflection of sound after it has hit something hard and distant.

Reverberation: It is the phenomenon whereby a reflected sound ray enters our ears in less than 0.1 seconds after the original sound wave. Since the original sound wave is still in our memory, we are unable to distinguish the difference between the original and reflected sound wave, thus we will hear the 2 sound waves as 1 prolonged sound wave as it has combined together.

Reverberation time:
Reverberation time is the time, in seconds, for the average sound in a room to decrease by 60 decibels after a source stops generating sound. The optimum reverberation time for a space in which music is played depends on the size of the room and depends on the material to be produced in the space. Rooms for speech require a shorter reverberation time than for music as a longer reverberation time can make it difficult to understand speech.

Echo VS. Reverberation: The largest difference between these 2 phenomenons would be the time taken for the reflected sound waves to go into a person’s ears. The reflected sound waves in reverberation enters a person’s ears in less than o.1 seconds while the reflected sound waves in echoes enters a person’s ears in more than o.1 seconds. Thus, we can clearly distinguish the reflected sound wave from the reflected sound wave in echo, but not in reverberation.

Diffraction: Diffraction basically refers to the phenomena experienced when a wave encounters an obstacle. It is the apparent bending of waves around small obstacles and the spreading out of waves past small openings.

Factors affecting diffraction are as follows:
1.Wavelength – We will not be able to change the wavelength in this case, even though it may affect diffraction
2.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 hence it is necessary to seal off whatever possible slits that may be present in the wall.
Interference: Wave Interference is a phenomenon which occurs when two waves meet while travelling along the same medium. There are mainly two types of wave interference: constructive and destructive

1. Constructive Interference: 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.

2. Destructive interference: The opposite of constructive 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. 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.

Superposition of waves:
The principle of superposition may be applied to waves whenever two or more waves travelling in the same medium at the simultaneously. The waves pass through each other without being disturbed or without being combined together. The net displacement of the medium at any point in space or time, is simply the sum of the individual wave dispacements. This is true of waves which are finite in length (wave pulses) or which are continuous sine waves.

3. Solution:
After some discussions, we have come up with a solution to set up a home entertainment studio, which includes furniture such as sofa and coffee table as well as a stereo sound system such that the sound quality can be maximized. This is the result.

1. Room
The room will be square in shape. The dimension of the room has also been decided to be at 34m by 34m for reverberation to occur since the speed of sound in air is approximately 340m/s. Reverberation is able to produce a better sound effect as the sound waves can combine together to form a prolonged sound wave which will make it sound louder. By making the room square, the sound effect will also be quite uniform in the whole room.

2. Carpet
Carpet is soft and fuzzy, thus by setting up a carpet on the ground; it will be able to absorb the sound waves when it reflects off the wall to the ground. It will ensure that there is no excess reverberation of sound waves as it will cause the sound to be muffled.
3. Stereo System
The two speakers will each be placed in a corner and will also be hung on the wall. This to ensure not too much sound waves that are produced by the speakers will be absorbed by the carpet on the floor and will be reflected off the walls instead. The speakers are also placed at the optimum distance away from the listener, hence ensuring that the sound waves have been thoroughly scattered and spread out before reaching the listener.

Through the use of an external online calculator, we have determined the distance of the optimum reverberation time to be 2.541790490341754secs, which is quite a long time, thus showing that our design is quite feasible. This will also help to ensure that the sounds do not sound too dead, muffled or too soft. The 2 speakers should also be placed at the maximum distance between them so that their sound waves do not interfere with each other as they are spread out.
For the stereo system, we will also be using one with a receiver having higher wattage. This will give a more detailed and dynamic sound and also a more versatile and powerful performance than one with lesser wattage, even at volumes low to medium.



4. Walls
The walls will be made of smooth concrete. This is to ensure that sound waves will be reflected and not be absorbed, hence maintaining sound quality and reverberation can also occur. Diffusers will also be placed on the walls to spread out the sounds waves in the room in all direction so that the room will not be so “dead” but instead have a livelier feel to it.
5. Furniture
The sofa will be placed in the middle of the room where constructive interference will occur so that the sound quality the listener receives is optimum. The coffee table will be placed next to the sofa so that it will not be in the way of the sound waves. At the same time, the listener sitting on the sofa will be able to enjoy coffee conveniently.
The disc cabinet will be placed at the back of the studio to make sure that sound waves produced by the speakers will not be interrupted. The sofa and coffee table will be of a very high mass as a higher mass ensures lesser absorption of sound waves. The coffee table and sofa will also be made of a hard material so that it can reflect the sound waves off.
6. Enclosed Area
The home entertainment studio will be designed in such a way that no external sound waves would be able to enter. This will help ensure that the sounds in the room are enjoyed in its original context and no external interference occurs. This will be achieved by making the walls as heavy and sturdy as possible instead of being hollow as sound waves can easily diffuse into a hollow wall. There will also be sound-proof windows set up so that sound waves will be kept outside of the room. For the door, weather-strips can be installed at the gap of the door or we can install a very sturdy door such that no sound waves are able to come in.
We can also install acoustic sound panels on the walls and ceiling and also install acoustic damping tiles on the ceilings so that sound waves do not enter through there.

Reflections
Difficulties faced as a group and how the group went about solving them:
1. We did not know which specific direction we should head in as the problem statement was very different from what we had done.
2. There was also difficulty in terms of collecting data.
3. Sometimes, we even have a conflict of ideas as there are a variety of answers we can explore. However, we managed to solve this problem through effective communication between the group members.
What we did well as a group:
1. Our group was rather consistent in developing our ideas as we constantly updated our mindmaps to show the development of our thinkings.
2. We were also very cooperative and we each contributed equally to produce the final product.
3. We were also able to internalise what we have learnt as we were able to rephrase the information we found on the net to the research report we produced on our blog.
4. Everyone also had their own share of ideas to share pertaining to this project.
How we can improve:
1. However I think our group could have improved in terms of collecting data as I feel that the data we collected maybe limited. This could probably be rectified by approaching other sources of information such as other websites, doing field research, going to the library, etc. Our group was rather dependent on the internet.

What skills we have learnt:
1. I have learnt how to researching and come up with solutions for a problem.
2. I have learnt to manage and prioritize my time, as research usually takes a longer time and I need to have a good sense of timing to achieve whatever I need to.
3. I have also learnt to work with my teammates given the short amount of time we have. I have also experienced real independent study as the PBL we are doing on is based on an entirely self-study topic.
4. I have also learnt how to think out of the box as this PBL allowed me to come up with creative ways of approaching the question.

How our critical thinking skills has been enhanced:
1. Given the vast amount of resources, I have learnt to pick out what I need and to use them in producing our solutions for the problems.
2. I learnt how to come up with solutions using different perspectives to combat problems effectively.

What difficulties we faced during the PB solving process and how we go about solving them:
1. There was difficulty in understanding most of the new terms like diffraction and wave interferences.

However this was easily solved by doing research.
2. In the course of the PBL, I may often get frustrated when I am unable to finish my tasks on time, such as researching on a certain topic, or when I am unable to produce the mindmap for our blog.

I have solved all these by learning to manage my time better.

3. Next there were problems determining the room acoustics so as to prevent the sound produced by the speakers from getting affected. This was harder as we had to look into many aspects such as the placement of the furniture and the materials of the wall e.t.c
However, after much discussion among the group members, we were all able to come to a consensus.
What further improvements could we have made?
1. I could also have done more detailed calculations to back up our proposal idea to make it more convincing.
2. I think I could have explored the question in much more depth and present it in a more detailed manner than the present one.

Posted by rainbowskies at 6:38 AM