Home - back to the cover page
Experiments - to all the experiments conducted on the four dishes
Conclusion - to the answer to the question on the dishes
Birds - all the bird calls recorded by the dishes
E-Mail - write back, with comments, crits.
This is a very basic approach to the Parabolic Sound Reflector Dish. This page basically outlines how the dishes were made in a very brief summary of the basic tests preformed on all the dishes. The reason for having a Parabolic Sound Reflector is so that sounds in the distance can be heard with ease without having to physically go to the source. This is useful in bird watching and spy operations. Our intentions are to continue our project because it brought such great rewards of knowledge, also because of advice received from various judges. We now want to see what the outcome of a comparison between different types of dishes would be. However just doing a comparison between the different substances, aluminum and fiberglass, is not going to yield sufficient knowledge, we are also interested in the type of amplifying units used, and extensions onto the best dish. Further more, we intend to place all information on the internet, where millions of people can view it. Also a program will be written that will be zipped and this can be down loaded for future reference. The application of this device - the Parabolic sound reflector - is Bird watching, and as such all experiments will be conducted in order to see which dish can be used in this field, if any. AIM
For simplicity we are going to call the four dishes by name Alpha, Beta, Gamma and Delta respectively, also we are going to have a control, a simple microphone with n amplifying unit attached to it. We expect Gamma will be the best, Delta second, Beta third and Alpha fourth because Gamma has all the improvements and Alpha has the least.
Our aim is to construct more dishes and make a comparison between the three to see what the difference would be between their receptive capability. What we then want to do is see which of the four is the best at receiving sound.
This dish is to be an exact replica of Beta only that instead of Aluminum as the medium we will use fiberglass. The microphone with be the same.Alpha: Being a very low budget, unprofessional dish. It will be made of aluminum with a simple amplifying unit and a more spherical shape.
Beta: This is last years dish which is near parabolic shape. It has a standard amplifying unit and we tried to make look as professional as possible.
Gamma: This is going to be the most sophisticated dish of all the dishes. It will have a high quality amplifying unit and is an amalgamation of all our past experience and advice. The battery will be attached to the wrist and the amplifier to the lower arm.
Delta:
The Control: This will simply be an amplifier and earphone setup to exact replication of all the other amplifiers save that of dish Gamma. It is just to make sure that the dish is the one responsible for the amplification than the amplifier is.
We also want to see if using the electronic amplifier LM380 chip will have any difference than using the filtered amplifier LM380. We also came up with various questions, and want to answer these by conducting several experiments.We want to allow millions of people to see this project, as some might want to construct a dish, to help them bird watch, as the commercial devices are expensive. So we want to make a home page, and place it on the net, however due to insufficient funds, this will have to be on a "free" site, which might be overlooked. Also we want to write a Turbo Pascal 6.0 program to speed up down load time so that it does not inconvenience the browser. And make a slide presentation, so that the information can be accessed easily and quickly.
The over riding AIM, is to find the dish that best rcords Bird calls. Since this device is used primarily for that purpose the AIM is to find the perfect home made dish, to do just that. (See Birds, for great detail)
THE MEANING:
In this section we discuss the meaning of "PARABOLA" and related words. Most people do not know what these words mean. As part of our research, we went to the Howick Library, searched on CD-ROM encyclopedia and even resorted to the Internet and this is the information that we found:From the "NEW OXFORD ILLUSTRATED DICTIONARY"
Parabola:(n) Plane curve formed by the intersection of a cone with a plane parallel to it's side. Parabolic-ical:(adj. s.) Of, like a parabola.
From the "THE CONCISE OXFORD DICTIONARY"
Parabola:(n) an open plane curve formed by the intersection of a cone with a plane parallel to its side, resembling the path of a projectile under the force of gravity.
From the "WORLD BOOK ENCYCLOPEDIA"
A parabola is a specialized type of curve. A parabola is formed by a plane that intersects a right circular cone that is parallel to one of its elements; that is, it is a CONIC SECTION or a parabola may also be defined as the locus of points that one equidistant from a focus point and a fixed line (the DirectX.) By using these latter definition a parabola may be constructed by ruler and compass. Parabola in terms of mathematics: The parabola is a plane curve formed by the intersection of a cone with a plane parallel to a straight line on the slanting surface of the cone. Each point of the curve is equidistant from a fixed point, called the focus, and a fixed straight line, known as the DirectX. The parabola is symmetrical about a line passing through the focus and perpendicular to the DirectX. For a parabola symmetric about the x-axis and with its vertex at the origin, the mathematical equation is y2 = 2 pr, in which p is the distance between the focus and the DirectX. A parabola is the curve that describes the trajectory of a projectile, such as a bullet or a ball, in the absence of air resistance. Because of air resistance, however, the curves in which projectiles travel only approximate true parabolas. Parabolic mirrors are ref-lectors that have the shape of a parabola rotated about the parabola's axis of symmetry. Parabolic mirrors reflect rays of flight in parallel lines from a light source at the mirror's focus.
WHAT IS A PARABOLIC REFLECTOR DISH?
The Parabolic sound reflector dish is basically an amplifying unit of sound as a whole. It is made in the shape of a cone - that can have many different depths and diameters. As sound waves hit the dishes interior they each bounce individually at ninety degrees off the surface eventually all passing through a single point named the focal point. At this point a microphone is placed to collect all the sound waves. From there an amplifier strengthens the volume of the sound and the sounds are heard.
Put simply it is a mechanical ear. The dish has the same principle of working as the ear.
How the ear works:
The pinna. or outer ear collects the sound waves and forces them down the ear canal, The sound reaches the ear drum, and the ear bones (namely the hammer, anvil and stirrup.) These amplify the sound. The amplified sound then travels into the cochlea.
The cochlea contains thousands of hair like cells. These cells convert the minuscule movements, caused by the amplified sound, into nerve impulses, which are then transmitted, by the auditory nerve, to the center of hearing in the brain.
How the Parabolic Reflector works:
The dish of the Parabolic Reflector collects and forces sound waves to the microphone, where they are converted into electronic impulses. From the microphone the sound impulses travel via a wire to the amplifying unit, where they are amplified. The amplified electronic impulses then travel to the headphones and are converted into sound waves that travel into the listeners ear.
To summarize:
 |
The dish collects sound as does the pinna( outer ear.) |
|
The car canal transports sound to the amplifying ear bones. The electric wire transports the electronic impulses to the amplifying unit. |
|
The bones of the ear( Hammer. anvil and stirrup.) amplify the sound. The amplifying unit amplifies the electronic impulses. |
|
The auditory nerve carries the impulses to the brain. The wire to the earphones carries the amplified impulses to the headphones. |
|
The brain registers the sound. The headphones, while not registering the sound, transmit the electronic impulses into actual sound thus allowing the user to register the sound. |
How the amplifying unit works:
An amplifier is any device or circuit that receives a signal, amplifies it (that is, makes it stronger), ideally without changing the signal in any other way and sends the signal out again, only stronger. Electronic amplifiers can be based on electron tubes or semi-conductor devices. The simplest electron tube that can perform amplification is the triode. However, in most modern devices, electron tubes have been replaced by semi-conducting circuit elements, such as the transistor. Our amplifier is even more advanced and we are using a chip amplifier.
Operation of Amplifiers:
The amplifier that we are using is based along the following explanation:
In a basic transistor amplifier, the transistors act as sources of current or voltage whose output value is larger than the input. As the input from the microphone enters the amplifier the output is in ratio to the input, obviously increased. This is called the gain of the amplifier. Other gains that are sometimes considered are the current gain, which is the ratio of output current to input current, and the power gain, the ratio of power output to power input.
How the earphone works:
An earphone converts electrical impulses into vibrations. The vibrations create little beats onto the thin film of material that then can be heard as sound.
MATERIAL INFORMATION
Gamma will have better parts and attachments than Beta and similarly for Beta to Alpha. For modifying the reverberations, we have two types of materials, sound-absorbent and sound-reflecting. Soft materials such as cork and felt absorb most of the sound that strikes them, although they may reflect some of the low-frequency sounds. Hard materials such as stone and metals reflect most of the sound that strikes them. Thus we are using aluminum to construct Alpha and Beta and Fiberglass for Gamma because commercially this is the material that is used and we want to get Gamma as - perfect as possible. After our experiments were conducted, we discovered that the material does not make that much difference (between fiber-glass and aluminum at least).
The microphone has a casing surrounding the structure that not only protects it but also gives the microphone a sense of direction. Some microphones called omnidirectional microphones have no direction and pick up sound from all directions. Others tend to pick up sound only in the direction you point. In this project an omnidirectional microphone will be best as sounds only come from the direction the dish is pointing. The way sound behaves will also play an important role in the accuracy of our project thus we are doing experiments to overcome each situation.
Speed of sound: This speed depends on the frequency and the medium that the sound is traveling through and not on the amplitude. Properties effecting the speed of sound are density and compressibility. The denser a medium is and the less compressible it is, the slower the speed of sound will be. Generally liquids and solids are more dense than air. But they are far less easily compressible, thus sound travels faster in these mediums.
MATERIALS
The materials we used had to be as light as possible as well as the cheapest available. This was one of our goals. The locating of the materials was easy, as well as finding the plans for construction. The list below has the exact materials used as well as the amount of materials used.
The materialsfor ALPHA:1 Circular piece of aluminum
1 Brass rivet
1 Sawn piece of aluminum piping
1 Piece of 2.5mm wire
1 Piece of 5mm wire
1 Wooden hammer
1 Sack of sand
1 Gas cylinder with torch
1 Can black spray paint
1 Can clear lacquer
1 camera and flash
1 Length electrical wire
1 Microphone jack
I Set earphones
1 Earphone jack
1 Roll black insulating tape
1 Crystal microphone
1 PM 9 battery
1 Battery clip
1 Tape box
1 Piece veri board
I LM380 integrated circuit
1 2.7 ohm resistor
1 .uF capacitor
1 100uF capacitor
1 10k ohm preset
I Soldering iron
1 Length solder
The materials for BETA:
1 Circular piece of aluminum
2 Brass rivets
2 Sawn pieces of aluminum piping
3 Brass strips
2 Pieces of rubber
1 Piece of cardboard
1 Camera with flash and film ( To document construction)
1 Sack of sand
1 Gas cylinder with gas torch
1 Wooden hammer
1 Can black spray paint
1 Can clear lacquer spray paint
I Newspaper
1 Glue
1 Sander
1 Length of electrical wire
1 Roll black electrical insulation tape
1 microphone jack plug
1 Set earphones
1 Ear phone jack plug
1 Lrv1380 integrated circuit chip
2 Capacitors
1 Resistor
1 Crystal microphone
1 PM9 battery
1 Battery clip
1 Preset (not utilized)
The piece of cardboard was for a template of the parabolic shape. The sack of sand was for a base on which to beat the dish. The gas cylinder and torch was for heat to anneal the dish as required. The electronic components were for construction of the amplifier. For the control assume that the components remain the same as for dish BETA. Without the aluminum or handles.
The materials for GAMMA:
1 Piece cardboard
I Can black spray paint
1 Can silver spray paint
16 Pieces 1" Styrofoam
1 Bottle wood glue
1 Hacksaw
1 Small metal hammer
1 lm2 piece of heavy fiberglass
1 Sandpaper
1 Bolt
1 Castle nut
1 Press stud
1 Tube Super glue
1 Drill + Bits
1 Axe Handle
The electronic components:
Eavesdropping amp:
Resistors: Transistors
R1:1.5m Q1:2N5089
R2:15k Q2 :2N5089
R3:330k Q3 :MPS652O
R4:1Ook Q4 :MPS652O
R5:10k potentiometer
R6:3.3k
DR7: I Ok Miscellaneous:
R8:lk
R16:680k SWIA,B,C : 2 pole linked switches
R9:680k SW2,3 : 2 pole switches
R10:4.7k Earphone jack
R11:1.5k 9v battery
R12: 1Ok potentiometer Battery clip
R13:10k potentiometer Crystal microphone
R14:lk veri board
R15:lk Wire
Soldering ironsolder
Capacitors :
C1 : l m f
C2 : 1 m f
C3 : 15 m f
C4 : 1 m f
C5 : .01 m f
C6 : .01 m f
C7 : .01 m f
C8 : .01 m f
C9 : .01 m f
C10 : .01 m f
C11 : 1 m f
C12 : 100 m f
Components Amplifier:
LM 380 chip
Resistors: Capacitors:
2.7k Resistor 1 m f
1Ok Preset 100 m f
Miscellaneous:
9 V Battery
Headphones
Battery clip
Crystal Microphone
Veri-board
solder
chip holder
soldering iron
wire
The simple Audio Amplifier:
Resistors:
R1: 1 Ok
R2: 68k
R3: Ilk
R4: 2.2k
R5: 10k
R6: 22k
Capacitors:
C1: 10 f16V Electrolytic
C2: 10 f 16V Electrolytic
C3:.01 f Disc ceramic
C4: 100 f 16V Electrolytic
C5:.04 f Disc ceramic
C6: 470 f16V Electrolytic
Semiconductor:
Tr 14: NP Type DS548 transistor or similar
D1: 1N 914 Diode
Miscellaneous :
T1: Audio coupling transformer 3k2 3k2
T2: Audio coupling transformer 1k2 8k2
8k loudspeaker
soldering iron
Veri-board
Crystal microphone solder
9V Battery
Battery Clip
The materials for DELTA:
All the components as for Alpha and Beta for the amplifier and the following.
4 packets of Fiberglass
2 cans of Resin
Sandpaper
Scissors
Catalyst
I Drill and bits
Beta as mould
Release agent
Furniture polish
Swimming pool
Knives
Screwdriver
Plastic packets
Grease proof paper
Handle
Microphone
Screws
All materials were relatively easy to obtain, however, some of the materials were scrap, and these were found at home, and thus might prove difficult to obtain.
METHOD
As with the original dish a diary was kept to record the events of construction. Cataloged for each major event that occurred, minor events were omitted for the sake of succinctness.ALPHA
Day 1: The aluminum was purchased. The first stages of softening began
Day 2: The aluminum was ready for moulding. This took place with a wooden mallet.
Day 8: The aluminum was in a dish like state. But kept bent slightly out of shape. Now sanding could begin (to smooth the dish).
Day 10: The dish is now smooth. The construction of the handle now began.
Day 12: The handle was fixed to the dish.
Day 13: Construction of the amplifier unit began.
Day 15: The amplifier was completed and attached to the dish.
Day 16: The dish was now polished and spray painted.
Day 17: The dish was completed, and now the experiments could begin.
Hammering,
with a hand created wooden hammer, to smooth and not tear the dish
BETA
Although Beta was previously made, a year before, the dish needed extensive repairs and was refitted with amore advanced microphone.
Day I: The aluminum was purchased. The first stages of softening began
Day 2: The aluminum was ready for moulding. This took place with a wooden mallet.
Day 6: The aluminum was in a dish like state. Now sanding could begin (to smooth the dish).
Day 8: The dish is now smooth. The construction of the handle now began.
Day 10: The handle was fixed to the dish.
Day 11: Construction of the amplifier unit began.
Day 13: The amplifier was completed and attached to the dish.
Day 15: The dish was now polished and spray painted.
Day 17: The dish was completed, and now the experiments could begin.
Attaching
the handle to dish Beta.
GAMMA
Day 1: The necessary parts were bought for the construction of the dish.
Day 2: 16 pieces of Styrofoam were glued together to create a solid block which was then smoothed down into an exact parabolic shape. A cardboard mould made from a graph of the parabola was used as a base. The Styrofoam was then covered with plaster of Paris.
Day 3: The mould was smoothed down to generate a perfect smooth mold for the fiber glass. Thereafter it was covered with a lacquer which then was absorbed into the plaster and began to eat away at the Styrofoam. The gaps were then filled with poly-filler and the mould smoothed down again.
Day 4: The fiberglass was spread out over the mould and left to dry overnight.
Day 5: The dish was removed from the mould taking the plaster of Paris with it, everything then had to be smoothed down so that there were no bumps on the inside of the dish.
Day 6: The dish was spray painted and the handle was attached.
Day 7: The amplifier was added along with the microphone.
Day 8: The experiments could begin.
DELTADay 1: The necessary parts were bought for the construction of the dish.
Day 2: Dish Beta, was covered in Vaseline to protect it. A cast, or fiber glass was mounted onto the dish, this allowed to dry. once dry, it was removed.
Day 3: The mould was smoothed down to generate a perfect smooth mold for the fiber glass. Thereafter it was covered with a lacquer which then was absorbed into the plaster and began to eat away at the Styrofoam. The gaps were then filled with poly-filler and the mold smoothed down again.
Day 4: The fiberglass was spread out over the mould and left to dry overnight.
Day 5: The dish was removed from the mould taking the plaster of Paris with it, everything then had to be smoothed down so that there were no bumps on the inside of the dish.
Day 6: The dish was spray painted and the handle was attached.
Day 7: The amplifier was added along with the microphone.
Day 8: The experiments could begin.
Amplifier
for Delta
STAND
We decided to construct the stand so that all three dishes could be displayed together in minimal space to make room for the other peripherals. At first we took a long metal pole which was then cut exactly into three and each part sanded down and covered with an antitrust solution. Then the pivot was welded onto the three poles creating a tripod. After that a suitable piece of wood was found and carved and sanded into shape, another plank was then glued and nailed into original piece for more strength. Later three holes were drilled one at each end and one in the center for the pivot. A piece of wattle was then selected to be ground and carved down into an impressive make-shift doweling rod to be slotted into the drilled holes to provide a peg for the dishes to slot onto. Finally all the parts were painted to look aesthetically pleasing. We kept the stand in parts so that it could be easily dismantled and carried around if used for some reason in the commercial field.
The
template and mould for dish Gamma
DIFFERENT PARTS OF THE DISHES
Filter:
Gamma has a filter attached to the dish but unfortunately it is not working. A filter is an electronic circuit that selectively passes or rejects electrical signals according to their frequency by means of a network of capacitors, resistors, and inductors. Filters are classified according to their function. A low-pass filter transmits signals that have a frequency below a specified level; a high-pass filter transmits only high-frequency signals.
Bandpass filters pass a narrow range of frequencies while rejecting signals having higher or lower frequencies. Band-elimination filters transmit all hut a narrow band of frequencies. An important class of filter is the active filter. Where as a conventional or passive filter attenuates some of the signal it is designed to transmit as well as much of the signal it is designed to reject, active filters use one or more Operational amplifiers to restore the level of the desired signal to its original amplitude. Filters are widely used in electronic circuits. They are used to reduce or eliminate electrical noise, enhance the quality of speech transmission systems, and eliminate fluctuations in the amplitude of an electrical current.
Amplifier:
An amplifier does exactly what the name means, it increases the volume of what ever the microphone picks up. In order to increase the amplification, amplifiers are often designed by connecting several stages in cascade. This means that the output of the first stage supplies the input signal to a second stage; the output of the second stage is connected to the input of a third stage, and so on. The overall gain of such a multistage amplifier can be determined from the basic definition of gain, or it can be found as the product of the gains of the individual stages. The modern equipment, such amplifiers are usually manufactured on a tiny square silicon wafer, about 2 mm (0.08 in)along each edge, and can have gains of 10,000 to 1001000 times. Our amplifier is a little larger about 50mm by 50mm and can have a gain of up to 50 000 times.
In order to obtain the required gain and to improve the matching of the input and output impedance's. two circuits may be combined in cascade form. It is also possible to use three-stage connections. This is especially advantageous when the circuit is in monolithic form on a single silicon chip, since all circuits and connections are fabricated in the same operation, and increased complexity of the circuit does not appreciably raise the manufacturing cost.
TYPES OF AMPLIFIERSAmplifiers can be classified according to the frequency range that they are designed to handle. For example, an audio amplifier is for the range from zero to about 100,000 cycles per second, or hertz; an intermediate-frequency (IF) amplifier is for 400 kilohertz (kHz) to 5 megahertz(MHz); a radio-frequency (RF) amplifier handles signal frequencies up to several hundred MHz; and an ultrahigh-frequency (UHF) amplifier employs specialized electronic devices that enable it to operate above 100 MHz. A special, monolithic form of amplifier has positive and negative inputs, giving an output controlled by the difference of the input signals, and is called a differential amplifier. This amplifier discriminates against noise and other inputs common to the two terminals. It is often used with various feedback circuits and is then called an operational amplifier (op-amp), because it was originally used for mathematical operations on signals, such as summation, differentiation, and integration.
FACTORS
When doing any project involving fieldwork there are always varying factors that must be taken into account. And depending on how you cope with the different factors, your conclusion may change. Our project is very dependent on certain factors.
Some of the factors are:
Temperature: If the air just above the ground is colder than the air above (in the morning) than the sound waves actually bend towards the earth in an are. Thus it is possible to hear a person from farther away.
Pressure: It has a scattering effect on sound which greatly diminishes it so hearing is not accurate. The pressure varies at different altitudes.
Humidity: This factor has a similar scattering effect as pressure. Humidity is not as big a factor as pressure though.
Rain: The noise of rain on the dish seriously decreases its ability to pick up sound.
Human: Each and every one of us has a hearing capacity which, in some, is better than others. This also effects the dish's ability to pick up sound.
Wind: This factor disperses sound to a much greater extent than humidity or pressure
Materials: The material that we construct the dishes out of does not make a large difference to the clarity and quality of sound that is picked up.
We know the factors and we must now over come them. so here are our solutions:
Temperature: Use a thermometer and work at an average of 20oC.
Pressure: It depends on altitude so we shall work at the same altitudes. Except for the Hilly and cliff experiment.
Humidity: Humidity will not effect the experiments very much therefore we shall not worry about its effects, as we cannot find a solution, nor do we have the equipment to combat it.
Rain: We shall simply not work in rain.
Human: All of us shall do each experiment and we shall calculate an average.
Wind: By the construction of a simple barometer/wind sock we will work at not more than 5km/hour.
THE USES OF THE PARABOLIC REFLECTOR DISHThe first recorded use of a Parabolic Reflector Dish was to help helmsman on board ships to listen for the fog horns from different ships and from coastal light houses. The helmsman would wear a pair of dishes mounted on a stand with a hole drilled through the center of the dish, with rubber tubing leading from the dish to the ear of the helmsman.
Now days the dish is used mainly as a receiver and sender of satellite, TV and radio waves. The dish can send sound as well as send radio waves etc. similarly it can also receive radio waves etc.
The dish also has uses for bird watchers. The dish can be made of a lightweight material and can be carried easily. The advantage of having the dish is that you can hear and locate the bird before you see it. Experiments into the accuracy of the dish were conducted, but these proved valuable to only static sources of sound, and the time it took for an accurate location of the sound source, would seem to long for a bird watcher hoping for just a glance of a bird, especially if the bird is agitated.
The most common use today is that in the world of espionage. Private investigators and police may use the dish as a bug - to eaves-drop on suspects.
Home - back to the cover page
Experiments - to all the experiments conducted on the four dishes
Conclusion - to the answer to the question on the dishes
Birds - all the bird calls recorded by the dishes
E-Mail - write back, with comments, crits.