Microphone

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Image:Microphone picture.jpg <ref>https://microphones.audiolinks.com/Samson/WirelessUHF/02289.jpg</ref> Image:large-stand.gif<ref>http://www.udmdjstore.co.uk/pictures/products/36066v374.jpg</ref>


This page is made for a project for Engineering_Design_II_-_Conceptualization_and_Realization_Course.

Contents

Executive Summary

This report examines the Samson microphone and Radio Shack microphone stand and boom extension. Through inspecting these products, we were able to determine their function, how well they work, their manufacture and assembly, failure modes and environmental impact. This information lead to several possibilities for future improvements.

The performance of the microphone was examined under normal use. It was found that there was a fair amount of noise in the microphone, and that the stand was somewhat difficult to reposition. Also, the sensitivity of the microphone dropped off severely when the source of the sound was more than a foot from the microphone.

The mechanics of the microphone and stand were explored as well. Through dissection and research, it was found that a plastic diaphragm inside the microphone vibrates according to incoming sound waves. It transfers its vibration to a permanent magnet moving through a coil of wire, creating a current by induction. This current becomes the signal which is sent to a speaker or recording device. The stand was build of hollow metal tubes held together by joints which allowed the position of the microphone to be adjusted. The assembly was balanced by a counterweight at one end of the boom.

The diaphragm and coil were modeled as a second order mass-spring-damper system. Using a Matlab simulation, it was found that the amplitude of the response is fairly constant op to around 9,000 Hz, and for higher frequencies, it drops off sharply. The implication of this is that the microphone will work well for frequencies under 9,000 Hz, and not as well beyond it. The human range of hearing is 2,000-20,000 Hz.

The methods of manufacturing the products were investigated. The stand and boom were built primarily of metal tubes of the same radius, and the microphone itself had a relatively low part count, and was fit together by simple means. Future improvements include automation of manufacturing, and design fro disassembly and repair.

Possible modes of failure were analyzed (FMEA). The most significant potential problem was the potential of the screw holding the boom in place to fall out. This could be solved by providing replacement rubber pads to the ones that sit inside the boom housing. Another potential problem is that there might not be enough coating on the wire that makes up the coil, causing a short circuit. This can only really be prevented by controlling the quality of the wire.

In assessing the impact of these products on the environment, it was found that the actual manufacture of audio-visual equipment has relatively little impact on the environment, leaving little room for improvement.

Stakeholders

The major shareholders of microphones and microphone stands are the consumers, retailers, manufacturers, transporters and society.

Consumer

  • Ease of use - Microphone must be easy to use, stand must be easy to orient. User should be warned not to point microphone at speakers to avoid feedback.
  • Ease of assembly - Microphone should be plug and play, stand should be easy to put together.
  • Effectiveness - Microphone should pick up sound without user having to be too loud while eliminating background noise, stand should hold microphone in desired place.
  • Ease of storage - Microphone should be easy to turn on and off and not require special storage, stand should be collapsible/occupy less space.
  • Reliability - Products should perform consistently without maintenance.
  • Safety - Product should not harm the user in any way.
  • Cost - Microphone is priced depending on its sensitivity but should be affordable, stand should be priced reasonably depending on quality.
  • Customization - Products should have replaceable or interchangeable parts for use in multitude of settings.
  • Portability - Products should be lightweight but sturdy enough to be transported.
  • Durability - Products should be easy to maintain and not break easily.


Retailers

  • Appeal - Products should attract customers.
  • Profit margin - Products should produce a profit so there is reason to carry product in store.
  • Storage - Products should be easy to stack and store.

Manufacturer

  • Material cost - The materials should be cheap and easy to obtain to maximize production and keep price down.
  • Manufacturing cost - The methods of manufacture should be cheap and efficient.
  • Standardization - Parts should be standardized to reduce complexity of design.
  • Assembly - Products should be easy to piece together in the factory.
  • Time for manufacture - Time should be minimal to produce in large quantities.

Shipping/Packaging

  • Weight - Products should be light to reduce transportation costs.
  • Durability - Products should be able to survive transit.

Society

  • Social Media - Musical concerts, gatherings, sports games, etc., that are dependent on capturing sounds to reach masses require reliable microphones.
  • Long distance communication - Reliant on microphone processing sounds so it can be transmitted to another location.

Product Function

Boom Stand

The purpose of the boom stand is simple: to be able to hold the microphone still in various orientations according to the user’s need. The boom stand which we dissected was designed to have 5 degrees of freedom, allowing the user to position the microphone in diverse settings. The stand and extension allows the user to adjust the total height of the two to a desired height between 33-61 inches. The joint connecting the boom shaft and stand has 3 degrees of freedom, allowing the shaft to pivot, rotate, and translate along its axis. The last degree of freedom is at the microphone holder, allowing the user to orientate the microphone at various angles. The microphone can be positioned at a low height downward angle for miking a drum set or high at various angles depending on the user’s height for stand up.

There are two rubber pads inside the joint connecting the stand and shaft. The friction between the surfaces of the two pads and the boom holder is strong enough to keep the entire boom stand above it still. At the same time the user can easily adjust (pivot) it. If there is too much force, whether it be too heavy of a load or a person pushing on it too hard, the force will simply overcome the frictional force and move the shaft so it won’t be directed to the pipes. One would almost have to be intentional to bend the steel pipes of the microphone stand.

The last benefit of the stand is that it is foldable and can be taken apart.

Microphone

A microphone is a type of acoustic transducer. This implies that it has the ability to covert sound energy into electrical energy. There are various types of microphones classified not only by method of converting energy but also by the directionality of use.

The microphone that we dissected was a dynamic, cardioid microphone. A dynamic microphone is one in which sound energy that enters through the head, hits a small, taut diaphragm which is placed directly above a magnet-wire coil combination. The incoming sound energy forces the diaphragm to vibrate which in turn vibrates the magnet inside the coils of wire. Due to electromagnetic induction, the movement of the magnet inside the coils of wire produces an alternating current (AC) inside the wire. It should be noted that a microphone's function is simply to relay the signals created by the changing incoming sounds to a more powerful device such as an amplifier. Therefore, the current produced inside the circuit of the microphone is not needed. All that is needed is information about changes in potential across the circuit. This is accomplished by setting the impedance within the circuit high enough such that current flowing is zero. Image:DynamicMic.gif<ref>http://www.mediacollege.com/audio/microphones/dynamic.html</ref>

The "cardioid" prefix mentioned earlier indicates the directionality of the microphone. Different microphones are necessary for different purposes. For example, in a situation where many sources of sound are required to be amplified through the same microphone, an omni-directional microphone would be required. On the other hand, for a single user a uni-directional microphone would be the obvious choice. A super-cardioid microphone is a uni-directional microphone with specific characteristics that are best understood from the following figure.


Image:Cardioid.gif

User Study

Microphones and microphone stands are used a lot by professional musicians. We first considered the manner in which some famous singers have used microphones and microphone stands.For example, Bono is a prolific microphone and microphone stand user.

In this clip: Bono with only microphone - Bono uses only the microphone while walking around the platform.

However, in this clip: Bono with microphone and stand - Bono stays relatively stationary while singing into the microphone that sits atop the stand.

In our opinion, the reason for this variation is because of the setting. While in the first clip Bono had the freedom to walk amongst his fans, in the second clip he was on a stage that simply faced the audience denying him the proximity to his fans.

For other musicians, the microphone stand is more of a necessity.

In the following clip Stephen Lynch and friend, comedian-musician Stephen Lynch needs the microphone stand because he is playing the guitar and singing at the same time. Additionally, one possible area of improvement that we noticed was that Stephen Lynch had to lean awkwardly over his guitar to reach the mic. If there were some way to have the space occupied by the guitar accounted for by the stand, it might make the lives of those musicians, who play instruments and sing simultaneously, much easier.

Lastly, we observed the variations in the distance musicians held microphones from their mouths. It seems that singing from further away reduces the volume but also reduces the unwanted noise/bad notes that a singer might inadvertently hit.

Setting up the microphone stand was relatively easy. Everything was intuitive and its 5 degrees of freedom allowed for all the desired orientations. The stand can be easily adjusted in mere seconds, and the microphone was turned on at the flip of a switch. The addition of the boom arm allowed the microphone to be raised over 7 feet, accommodating most users. Attaching the microphone clip to the boom arm wasn't as straightforward. Microphone clips are not standardized, different manufacturers make different sizes, causing us to go out and buy another microphone with an appropriate size.

During the testing of the microphone system, we found that:

  • Microphone was not very sensitive, we had to talk fairly loud for it to register.
  • Microphone will not pick up speech-level sound from more than a foot away.
  • The joint in the microphone clip is very loose, its hard to keep the microphone in position.
  • Solder inside microphone was loose, microphone stopped working after a few on-off switches.
  • Microphone only picked up sound that originated directly in front of it. All other sounds were muffled.
  • Microphone picks up a lot of static, background noise.
  • It makes me sound so bad.

Image:tn_079.jpg

Assembly

  • Note: Refer numbers from the Part List Section

Image:Assembly1.jpg

Image:Assembly2.jpg


Image:Assembly_microphone.jpg

Image:Subassembly.jpg

Mechanical Analysis

Objective: To simulate the frequency response of the acoustic transducer component of our microphone. This will help us determine the working range of the microphone.

Theory: 1) A dynamic microphone works by converting incoming sound energy to electrical output.
2) This conversion is carried out in the magnetic cartridge just below the head of the microphone.
3) As sound waves enter through the head, they strike the diaphragm.
4) This causes a transfer of energy to the diaphragm which in turn begins to vibrate.
5) The vibrating diaphragm causes air molecules trapped underneath it to vibrate. These in turn push down on a coil of wire that surround a magnet.
6) The movement of the coil around the magnet results in the electromagnetic effect as outlined by Faraday and Lenz.
7) This electromagnetic effect produces an alternating electric current in the wires.

Assumptions: 1) The diaphragm can be modeled as a mass-spring system (harmonic oscillator) with damping.
Image:mass_spring.png
2) The incoming sound energy has a sound pressure of around 0.632 Pa. This should correspond to moderately loud singing. Sound Pressure Levels Table. Note: the indicated value of sound pressure for moderately loud singing was chosen subjectively.
3) The above sound is transferred entirely to the diaphragm of the microphone without any energy loss.
4) Air trapped beneath the diaphragm is incompressible. This assumption was made because of the low absolute velocity achieved by the magnet as well as diaphragm.
5)The spring constant of the diaphragm is as a result of the tension that is intentionally induced during manufacture and is equal to 50 N/m. This value is a conservative value for the tension of a diaphragm as described by Patent with diaphragm tension value.Note: We sent an inquiry to Samson Audio the manufacturers of our microphone, requesting details about the diaphragm and magnet. They replied that they would be unable to provide those details because of intellectual property implications.
6) Room temperature (300K) and pressure.
7) The diaphragm is a thin disc of mylar.
8) The magnetic field strength of the neodymium magnet disc used in the setup is approx. 0.2 teslas as reported by magnet strength figure.
9) Number of wire coils was 50.
10) When the coil rotates around the magnet, any one wire goes from experiencing maximum positive magnetic field strength to maximum negative field strength in one half cycle.

Given: 1) Spring constant (k) = 50N/m
2) Dynamic viscosity of air at 300K (b) = 1.983*10-5N.s/m2 viscosity of air source
3) Sound Input pressure = 0.632 Pa
4) Acting diameter of diaphragm = 12*10-3m
5) Thickness of diaphragm = 0.1*10-3m
6) Density of mylar diaphragm = 1.390 kg/m3
7) Magnetic field strength(B) = 0.2 teslas

Calculations:

First mass of the diaphragm was needed:

Volume = Face Area of diaphragm * thickness

      = pi * (12*10-3m)2 * (1/4) * 0.1*10-3m

We know that Density = Mass/Volume

Therefore, Mass= Density * Volume

Mass (m)= 1.390 * 1.1310*10-8 = 1.5721*10-8kg

Now, having all the constants we could use Matlab to solve for the equation of motion of the mass-spring system.

Equation of mass-spring system :

mx" + bx' + kx = Force_Input where Force_Input is an initial condition applied force called Force_Input

Deriving the transfer funtion of the above equation we concluded that,

G(s) = 1/(ms2 + cs + k) where G(s) indicates the transfer function for the given mass-spring system.

This transfer function was then entered into Matlab's inbuit Bode function and the Bode magnitude and phase plots were obtained as shown below.

Image:Bode.png


Note that the frequency domain of the plots ranges from approximately 126 rad/s to 1E+5 rad/s. These limits of the domain correspond to 20 Hz - 20,000 Hz i.e., the human range of hearing.

From the plots we can see that this transducer system gives a very constant amplitude modification except for around x=5.71E+4 rad/s or around 9000 Hz where the frequency response quickly approaches 0. Beyond this minimum, the frequency modification quickly rises again and approaches a maximum at x = 1E5 rad/s or around 20,000Hz.



Parts List

  Microphone Stand Parts
Part Number Photo Part name Mass (g) Notes Material Manufacturing Method
1 Image:ring.jpg Ring (2x) 2 Attaches to microphone end of boom shaft Steel Machining
2 Image:img0185.jpgBoom shaft 493 Steel Pipe(mass includes counterweight) SteelExtrusion
3 Counterweight - SolidSteel Casting
4 Image:micholder.jpgMic Holder 10 Holds the microphone in place, allows the user to pivot the microphone up or down, giving the whole system an extra degree of freedom PlasticMolding
5 Image:bolta.jpgBolt A 3 holds mic holder to #7 Connection A Steel Machining and Threading
6 Image:boltb.jpgBolt B 2 #6 Bolt B can be screwed into #5 Bolt A Steel Machining and Threading
7 Image:connectiona.jpgConnection Part A 12 screws onto the boomPlasticInjection Molding
8 Image:connectionb.jpgConnection Part B71 Connects with #7, allows boom shaft to be pivoted, given the whole boom stand an extra degree of freedom SteelCasting and Threading
9 Image:pad.jpgRubber pad (2x) 8 The two pads go inside #8 Connection B to hold #11 Boom holder. The friction between the surfaces of the two pads and the boom holder is strong enough to keep the entire boom stand above it still. At the same time the user can easily adjust (pivot) itRubberMolding
10 Image:boltc.jpgBolt C 16 Bolt that goes through Connection Part B, the rubber pads, and the Boom holder, connecting them all together, there is a nut that is paired with the boltSteel Machining
11 Image:boomholder.jpgBoom holder 65 has a long hole in which the boom is inserted. Attaches to mic stand via #8 Steel Casting and machining
12 Image:wash.jpgWasher 1 #10 goes throught this washerSteelStamping
13 Image:handlebar.jpgHandle 28 Has a threaded hole in which the end of #10 is insertedSteelCasting and machining
14 Image:thumbscrew.jpgThumbscrew (2x) 3 Acts as a tighener to hold the boom in place. Goes into a hole in #11 Boom holder. The second one goes through the #19 Tripod Core and fixes the #16 Boom to it.Has plastic nub so as not to scratch the boom, which keeps the sprayed finish from being damaged Two kinds of plastic (head and nub) and steel (screw) Molding (plastic) and machining (steel)
15 Image:clip.jpgWire clip 2 Attaches to mic stand, used to hold wire in place Plastic Molding
16 Image:stand.jpgStand Steel pipe. It is essentually the body of the stand, there's a # 17 Fastener Connector between them for the user to adjust the two (Stand and Extension) to a desired height between 33-61 inchesSteel Extrusion
17 Image:extension.jpgStand Extension Steel pipe, the extension has a thinner diameter so it may fit in the # 16 Stand itself. The end of the extension is exploded out so that it can't be easily taken off.Steel Extrusion
18 Image:fc.jpgFastener Connector Plastic fastener connector reinforces tightness, preventing slippingPlastic Injection Molding
19 Image:core.jpgTripod Core Connection between the #16 Stand and the tripod legs of the stand, also serves as a weight to lower the center of mass and prevents the stand from tipping. The #14 Thumbscrew fixes the body to it and the legs are attached using #20 nuts and boltsSteel Casting and Threading
20 Image:nb.jpgNut and Bolt (3x) Used to fasten the legs to the Tripod coreSteel Machining and Threading
21 Image:leg.jpgLeg (3x) One of the ends of the legs was clammed for a tighter fit to the Tripod core, which also allows the #20 bolts used to be shorter Steel Extrusion
22 Image:ends.jpgRubber Ends These ends go on the other end of the legs. Their main function is to increase friction when in contact with the floor to prevent sliding from occuringPlastic Molding


    Microphone Parts
Part Number Photo Part name Masss(g) Notes Material Manufacturing Method
M1 Image:tn_132.jpg Switch slider <1 Allows user to turn microphone on and off Plastic Molding
M2 Image:tn_131a.jpg Sticker A <1 Applied to M1 to denote on and off directions Plastic Stamped out of a thin sheet
M3 Image:tn_131b.jpg Screw A (2X) <1 Holds switch electronics to the microphone body Steel Machining
M4 Image:tn_131c.jpg Screw B <1 Attaches ground pin to the back of the microphone body SteelMachining
M5 Image:tn_141.jpg Body 187 Large, machined Metal Casting and machining, sandblasted finish
M6 Image:tn_143.jpg Rubber disc 2 Holds three pins in place, so they line up with the holes in the cable that attaches to the microphone. Rubber Molding
M7 Image:tn_148.jpg Pin 1 Transmits signal from the microphone to the wire Metal Casting
M8 Image:tn_147.jpg Switch electronics 3 Use physical user input from switch to affect electrical circuit Plastic housing, metal wire Molding (housing), extrusion (wire)
M9 Image:tn_155.jpg Foam cover <1 Covers the magnet and diaphragm Polymer foam Stamping out of a foam sheet
M10 Image:tn_158.jpg Plastic cover 2 Protects diaphragm and magnet Plastic Molding
M11 Image:tn_162.jpg Chip <1 Takes signal from coil (M13) and transmits it to the the pins. Is glued to a slot on M16 Silicon chip, copper conductors Chemical etching
M12 Image:156b.jpg Diaphragm <1 Made from a thin piece of plastic with a spiral stamped into it to give it better elastic properties Plastic Stamping
M13 Coil <1 Thin insulated copper wire Copper Extrusion
M14 Magnet 5 Attached to diaphragm Magnetic metal Casting
M15 Sticker B <1 Covers cavity in the housing, below where the magnet sits Plastic Stamping
M16 Image:tn_154.jpg Housing 10 Holds parts M11-M15, the parts that actually convert sound into an electrical signal Plastic Molding
M17 Image:091a.jpg Wind screen <1 Made of a hollow foam ball. Inserted into the metal screen. Used to soften sounds of users' voices Polymer foam Part was stamped out of a sheet, and then likely heated and wrapped around a spherical mold.
M18 Metal screen 49 Made of a wire mesh attached to metal rings Steel Wires were extruded and woven into the ball shape. The metal rings were likely heated and pressed onto the ball.

Design for Manufacturing and Assembly (DFMA)

Design for Manufacturing

Materials: Plastic and Metal

Engineered products can be made out of a variety of materials. Depending on the application the choice of materials can allow a product to perform well or cause it to fail. Even among appropriate material choices, some materials have advantages over others for a number of different reasons. The parts that construct the boom stand and microphone are mainly constructed of either plastic or steel. In general, plastics can be good for inexpensive, complex shapes, while metals are good for it's durability and long lasting applications.

The category of plastics as a whole also has advantages and disadvantages. It is generally relatively easy to create highly complex plastic parts, with both small and large features, and with high aspect ratios. This is because plastics are easily molded in a variety of ways. Plastics also tend to be less dense than metals. From an aesthetic perspective, some plastics can be used to create unique shapes for beautiful products. However, many people tend to associate plastics with cheaper products, which can be both an advantage, or a disadvantage. For example, plastic is a good material choice for single-use forks and knives, but these utensils will never look as good as metal utensils. A major disadvantage of plastics is that they are usually made out of petroleum, which is an unsustainable resource. However, progress is being made in creating plastics from organic materials.

Another major materials category is metals. Metals tend to be very strong in both tension and compression, and tend to have a very long life span. They are less likely to deform than plastics, which makes them good for high-precision applications. From an aesthetic perspective, metals have a unique place in the human psyche. Metals also have a unique luster that people often find very appealing. The major disadvantages of metals are the potential to rust (depending on the type of metal), and the fact that they need to be mined, which can often be an inefficient process that causes a lot of environmental damage.

Microphone:

During the disassembly, one issue we encountered was removing part M6 from the body. M6, a rubber disc used to hold the pins in place, seems to have been attached to the base via a strong adhesive. Although this manufacturing method makes dis-assembly difficult, it is ideal for this product. The pins need to line up perfectly with the holes in the cable, possibly thousands of times during the product's life span. This means that the rubber disc must not be allowed to shift within the body. Even thought the disc is already press-fit inside the body, it is important that it is securely joined as well.

One possible area of improvement is in the soldering of electrical components and wires. Inconsistency in the soldering could be a sign that this was performed by hand. Automating this process would not be very difficult; both the chip and the switch electronics are rectangular. Considering the high volume of microphones being produced, it would be feasible to create a soldering rig that would quickly attach wires to the components.

Boom Stand:

The few parts that plastic (handle and end of thumbscrews) along with the rubber ends on the bottom are most likely made through injection molding. Injection molding provides a high volume mass production of identical parts with very low tolerance. The initial tooling costs are very high but the unit costs are low (meaning a high initial fixed cost but in exchange the marginal cost per unit is sufficiently low), thus when a large quantity of identical parts are produced injection molding will save money in comparison to other processes.

The counter weight on the end of the boom shaft and the tripod core are both solid pieces of metal made through the casting process. The counter weight is then either press fitted or glued onto the end of the boom shaft. The casting process (my guess is die casting) has a similar manufacturing feature as injection molding cost-wise. They are generally a high volume production with high initial tooling costs but low unit costs.

All the steel tube components have identical thicknesses and diameter, meaning that they can all be produced by the same machinery while each part is cut into the desired length. The raw steel is cast then made into a pipe by stretching the steel out into a tube. The steel tubes are seamless, which are suitable for the job as the shafts for being strong, durable, and light weight. The exterior of all steel components are sprayed on a metta-black finish for a good look to appeal to the consumers.


Design for Assembly:

The assembly of the parts can be either by man or machine. In our opinion, it would make more sense to use man power instead of having the assembly process be automated. To our surprise, the after the stand was dissected and analyzed it took less than 5 minutes for a single person to reassemble everything part together. Pliers were the only tool needed for the process, used for tightening bolts.

Failure Modes and Effects Analysis

Considering ways in which a product could potentially fail is an important part of the design process. All products should be designed so that they are safe and reliable for use. Potential dangers must be eliminated before production. FMEA reports identify potential failure modes and assign corrective measures. Risk priority numbers (RPN) are calculated (S*O*D) and then assigned to each failure mode to assure proper prioritizing. Higher RPNs are addressed first. The scale used for measuring S,O,D can be found in the Engineering Design textbook by Dieter and Schmidt. <ref>Dieter, E and Schmidt, L (2008). Engineering Design. Fourth Ed. McGraw-Hill.</ref>

S= Severity of Failure
O= Probability of Occurrence
D= Detectability of Failure


Assembly/Parts Failure Mode Consequence of Failure S Causes of Failure O Prevention D RPN Recommendations Responsibility
On/Off Switch Soldering Becomes Loose Microphone will not turn on 5 Bad soldering 6 N/A 2 60 Check soldering before assembly Controls engineer
Diaphragm Torn Diaphragm Inoperable 5 Misuse or Outside particles gets inside microphone 1 Foam Cover 2 10 N/A N/A
Wire Coil Torn Microphone inoperable 5 Improper use/production 1 Testing during production 6 30 N/A Controls Engineer
Wire Coil Inadequate coating to separate each wire Decreased electromagnetic effect 4 Improper use/production 1 N/A 8 32 N/A Controls Engineer
Magnet Looses magnetism Decreased sensitivity of microphone, inoperable 4 Over time or microphone is subjected to strong magnetic field 1 N/A 7 28 Don't go near extreme magnetic fields N/A
Microphone Housing Broken Microphone in pieces, wires exposed 5 Impact 1 N/A 1 5 Do not drop on floor after serving someone N/A
Microphone Clip Loose Joint Unable to orient to desired location 3 Loose Screws, wear from use 6 N/A 1 18 Tighten Screws constantly, add friction to joint Controls Engineer
Microphone Clip Broken clip Unable to attach to microphone 4 Improper use, impact 4 N/A 1 16 N/A N/A
Boom Stand Screw Loose fastener Unable to stay in position, falls down 7 Improper use, wear 3 Rubber pads inside boom housing 2 42 Replace rubber pads to ensure boom stays gripped in position N/A
Extending Stand Grip fails Stand does not stay extended 7 Wear from lots of use 2 Exploded end 1 14 Add rubber stoppers or grips Design Engineer
Rubber Pads Worn down thickness Boom shaft is unstable, gravity overcomes friction force 3 Worn pads 1 N/A 1 3 Do not pivot shaft aggressively or unnecessarily N/A
Rubber Ends Torn or lost Stand may slide 2 Worn down ends 1 N/A 1 2 N/A N/A
Cord Clip Broken or lost Loose Cord 1 Misuse 1 N/A 1 1 N/A N/A
All steel/metal parts of stand (Stand, tripod legs, boom arm , etc) Oxidation Aesthetic value, uncomfortable to touch 3 Neglect, exposure to water 2 N/A 1 6 Anti-rust finishing Controls Engineer
Microphone Feedback High pitched noise/static 3 Pointing microphone at speakers 8 N/A 1 24 Add warning label telling user not to point microphone at speakers N/A

From the generally low RPNs, we can see that this product is extremely safe and only has one part (falling boom stand) that could potential harm the user. Most problems can be avoided with a product test before packaging.

Design for Environment

In designing a product, it is important to consider the environmental effects along with the consumer. Conducting a Life Cycle Assessment (LCA) can improve the product's environmental-friendliness and reduce costs in the long run.

Toxic Release

This table and graph show the amount of toxic release into the environment. Note that the amount released by specifically the manufacture of audio-video equipment is minuscule compared to the other sectors involved.
Image:dfe-toxic.jpg Image:dfe-toxicpie.jpg

Energy

Since the product is heavily based on electrical power, this table shows the energy breakdown. Power generation is also the main sector here.

Image:dfe-energy.jpg

Greenhouse Gas Emissions

Greenhouse gases, such as carbon dioxide and chlorofluorocarbons, contribute to the prevalent problem of global warming. With a $1 million injection into the Audio-Video Manufacturing sector, the overall global warming potential (GWP) increase by 574 metric tons of CO2 equivalent.
Image:dfe-greenhouse.jpg Image:dfe-greenhouse-pie.jpg
As we can see from the graph above, the actual audio-video manufacturing process only contributes 19.7 MTCO2E, less than 4% of the total. Most of the emissions come from power supply. If a CO2 tax was passed, the manufacture of audio-video might take a hit, but not as hard as most of the other sectors. For a $30 CO2 tax rate, the production of a single microphone would only incur a minute tax of $.02. The stand would also incur just $0.02. On the user's end, they would have to pay $0.32 extra to run the microphone due to the severe CO2 taxes on power generation.

Air Pollutants

Conventional air pollutants such as carbon monoxide largely affect weather patterns like causing smog which in turn can cause respiratory and other health problem in affected areas. Most of the problem comes from power generation and the manufacture of petroleum. Audio-video manufacturing was not even in the top 10 pollutant sources.
Image:dfe-airpollfixed.jpg

Production vs Use

Image:production vs use.jpg
As we can see, most of the cost comes from the use of electricity when operating the product.

Conclusion and Recommendations

Our assessment of these products is that, overall, they are well-designed. There were several issues that should be resolved in other products if they are to be competitive. First of all, it was found that that there was a fair amount of noise in the signal and that the microphone was difficult to maneuver. These problems should be the first ones to be taken care of.

The manufacture of the products seems to have been done in the simplest way possible. Disassembling the microphone, however, was difficult, and future design iterations should take into account the need for customers to take the microphone apart and repair it. Also, the soldering process could be automated, if it hasn’t been already.

Upon analyzing the mechanics of the system, it was found that there is a lot of sound energy that is wasted. This leaves the potential of a sound harvesting device. The manufacture of the product has very little impact on the environment. The only potential to make the products more eco-friendly is to improve the energy efficiency of the products themselves or the methods used to manufacture them.

Team Members and Roles

Luo Xing Ni- DFE, Stakeholders, FMEA, User Study
Daniel Liptz- Parts List, Executive Summary, Conclusion, Assembly, DFMA
Justin Yi- Parts List, Assembly, DFMA, Product Function
Nakul Gupta- Mechanical Analysis, Product Function

References

<references/>
Note: For sourced images, the reference can be found by clicking on the image. For values used in mechanical analysis, the source link is provided alongside.

Appendix

Matlab Main

clc;
% Mechanical Analysis

% 1) Mass of diaphragm

diameter=0.01905;

thickness = 0.1*10^-3;

density = 1.390;

Area= pi()*diameter^2/4;

Volume = Area*thickness;
mass = density*Volume;

% 2) Spring constant of air enclosed

adiab_const = 1.4;
atm_pres = 101325;
air_length = 0.00635;

k = adiab_const*atm_pres*Area/air_length;

% 3) External force on diaphragm

Sound_input = 0.632;

Force_input = Sound_input * Area
<br

Bode Plot Code
%Boce_model.m

mass = 1.5721e-008 ;
%Force_input =7.1478e-005*2*abs(abs(sign(t-1))-1);
k= 50;
b=1.983*10^-5;
Area= 1.1310e-004;
w= [20*2*pi:10:20000*2*pi];

Num = [0 0 1];
Den = [mass b k];

sys = tf(Num,Den);
bode(sys,{20*2*pi,20000*2*pi});

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