The science of the sound wave is important in everyday life, from its use in car mufflers to the high tech office. In this paper I’m going to talk about the sound wave and describe its characteristics, show how this science was applied to muffler design, and computer design.
Sound is a pressure wave that consists of tiny fluctuations in the air pressure. The amplitude in general, is the maximum change in value of a parameter during the oscillation of a wave. In amplitude, that parameter will usually be pressure. The amplitude of a sound is the loudness of the sound. In illustration, this is the distance between a peak or trough. See illustration on previous page.
The frequency is defined as the number of vibrations, oscillations, or cycles in a repeating process occurring per unit time. In the context of sound, it is the number of compressions passing a fixed point of reference in one second. The resulting unit of frequency is called Hertz (Hz).
Frequency is perceived as pitch.
Intensity is the rate at which sound energy flows through a defined area. Since the flow of energy is power, the dimensions of sound intensity are power/area. Usually, sound intensity is measured in watts/meter2. Intensity is perceived as loudness.
Radio Waves In the modern society, radio is the most widely used medium of broadcasting and electronic communication: it plays a major role in many areas such as public safety, industrial manufacturing, processing, agriculture, transportation, entertainment, national defense, space travel, overseas communication, news reporting and weather forecasting. In radio broadcasts, they use the radio waves ...
Interference is a synonym for superposition. Constructive interference is the amplitude of the combined wave, which is created by superposition and is greater than the amplitude of either component wave. Destructive interference is the amplitude of the combined wave created by superposition and is less than the amplitude of either component wave.
Superposition is a concept that describes the way in which sound waves, and waves more generally, interact. In essence, two waves passing through the same point in space at the same time combine in a linear fashion to create a single new wave. If the displacement from equilibrium caused by the first wave equals “a” and the displacement from equilibrium caused by the second wave equals “b”, the resulting displacement from equilibrium for the combined wave will be “a + b”. This is an algebraic addition. Since “a” and “b” can be positive, negative, or equal to zero, the resulting sum can also be positive, negative, or equal to zero.
The period is the time required for a single wavelength to pass a fixed point of reference. The period of a sound wave is the inverse of its frequency. The phase of a wave is an expression of how far through its cycle of oscillation it has progressed. Because the mathematical description of wave motion is similar to the mathematical description of motion in a circle, wave phase is expressed in degrees or radians.
A wave completes its cycle in 360°, just as a circle is completed in 360°. Half a cycle is 180°, and a quarter cycle is 90°. The relative phase of two similar waves is a measure of how synchronized they are.
The speed of a wave is the ratio of distance traveled to time required, for example, the distance traveled in one second. The speed of sound is no different than the speed of an object. Usually the speed of sound is thought of in terms of one cycle of a wave. In one cycle, sound travels a distance of one wavelength. The time required for one cycle is the period, so the speed is the ratio of the wavelength to the period. Dividing by the period is the same as multiplying by the frequency, so the speed of a wave is often expressed as the product of wavelength and frequency.
METHODOLOGY Two experiments were done last time due to some circumstances that made the class to lack time and to be late compared to the official class syllabus. The students were able to accomplished the job by equally dividing the time into two. The first experiment was about Kundt’s tube. In this experiment, longitudinal sound waves will be produced in a metal rod and an air column. Using the ...
The wavelength is the distance between one peak or crest of a sound wave and the next corresponding peak or crest. The product of the wavelength and the frequency of a sound wave yields the velocity of that wave. The waveform is the detailed way in which a parameter changes during the oscillation of a wave. For sound, that parameter will usually be pressure. In practice, this is the shape of a wave on a graph. Waveform is perceived as timbre.
The muffler of the car is part of the exhaust system, which carries out several functions. They are getting hot, noxious exhaust gasses from the engine to a place away from the engine compartment, significantly muting the noise output from the engine, and in the case of modern cars, reduce exhaust emissions.
The exhaust system includes many parts for doing the functions listed above. Included in the picture below the exhaust manifold, “y” pipe, catalytic converter, resonator, exhaust pipe, muffler, and tail pipe.
The muffler’s job is to muting sound output and is preformed in many ways. The three ways that it accomplishes this task is absorption, restriction, and reflection. They can use all three methods or just one, they all work. I am going to elaborate on the reflection method because it mutes sound the best.
A reflection muffler is the type of muffler that I will be elaborating on. It is the most sophisticated type of muffler. They often utilize absorption principles in conjunction with reflection to make the ultimate high-performance silencer. The sound wave is used against itself in the reflective muffler. When two like waves collide, they “cancel” each other and leave no energy except a spot of low-grade heat.
Conventional reflection mufflers use U bends within the muffler to reflect the flow and sound back and forth in a S curve through the body of the muffler. This type of muffler provides the most sound volume reduction. Chambered mufflers have angled walls within the muffler body to reflect the sound and flow from side to side. If you ever decide to open up one of these mufflers it is easy to see the restrictions within. There will be areas of heat discoloration on the side of the muffler anywhere there is a restriction in flow. This is usually at the first V wall separating flow and the first reflection back toward the middle of the muffler.
A sound wave is a disturbance. When it travels through air, it bounces the air molecules around and they vibrate. They then hit other molecules and cause a chain reaction. In a different material, such as metal, sound actually travels faster. this is because the molecules are much more tightly packed (water is not dense because the molecules just roll over each other, and air is even less dense, ...
There are numerous ways and engineering tricks to make a reflective muffler, too. Hedman Hedders made a muffler that looks a lot like a glasspack with a catch. The outer casing is sized so that high-pitched engine sound is reflected back into the core of the muffler. Where those high-pitched waves meet their death is where they slam right into a torrent of more sound waves of like wavelength coming straight from the engine.
This is a 2000 Eclipse GT Stock Muffler. In this muffler, all the sound must pass through the small-perforated holes in the short pipe in the first chamber. The second larger chamber is more of an echo or resonance chamber for sound reflection. The exhaust then flows out the pipe to the tip with its own little muffler built into it. In these designs one can see that the science of the sound wave is applied in muffler design. In reducing the loudness of the sound wave the used interference by a reflection chamber where these sound waves are used in superposition to destroy each other by colliding into one another, canceling out.
Another unusual application of sound wave science is in the design of office equipment. People like their equipment to be very quiet. In the case of building computers, when they are complete with all of their components running, they have to pass a certain decibel level. The dB level is the intensity or amplitude of the product. In one case, a product was made and passed the dB test and was put out on the market. Then there were many complaints because the machine claimed to be really loud. The engineers felt the same way too and ran the dB tests on it again and again and every time it passed the dB specifications. Finally, they came to the conclusion that it was the fan that was making the sound and it wasn’t the dB rate that was high, it was the frequency of the sound. To pass high frequencies sound the intensity doesn’t have to be that high. So that is why the fan passed the test but still had a pitch, which was noticeable and irritating to the human ear (Desai N.Pag.).
Sound is part of our everyday lives. Just like we have eyes for, we are given ears for hearing sound. We rarely take the time to think about the characteristics of sound and the ways that they are made. The basis for an understanding of sound and hearing is the physics of waves. Sound is a wave, which is created by vibrating objects and spread through a medium from one location to another. In this ...
In conclusion, the science of sound can be used in everyday applications. The mechanics of a muffler and the dB’s of a fan are just a few examples. The physics of sound will continue to evolve as human being continues to advance in technology.
ISUZU, “Performance Exhaust System Basics”, <http://www.isu
ANC, “What is Sound”, <http://www.signalsystemscorp.com>,
Teo, Alvin, “Exhaust Flow in an Automobile”, < http://www.
NSX Prime, “Exhaust Theory”, <http://www.nsxprime.com>,
Road Race, “3G Eclipse Exhaust Pics and Info” < http://www.