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Client Comments on Report 1

We received your report, and we have some comments and questions. It sounds like you have identified a few opportunities for improvement including noise reduction, sensitivity / efficiency improvements. Please respond point by point to the items below. We are looking forward to seeing your ideas in Report 2.

• Executive Summary: Clear coverage of findings in each area. Would be better if shorter (~50%) and more concise covering only most interesting or nonobvious findings (e.g.: don't need to tell client that manufacturer and retailer are important stakeholders to consider, but if there are important needs specific to the design of the product, could mention those).
  • Made the summary more concise and focused on recommendations and how we arrived at them.

• Stakeholder Needs: Good list of needs. Some appear to be missing such as durability, ability to turn on/off, avoidance of background noise and feedback, quick to adjust, etc.
  • Updated stakeholder's needs to reflect additional issues.
• Use: Good description. How long does it typically take for a user to set up the microphone, and how long does it take to adjust all of the degrees of freedom to get the microphone into a comfortable position?
  • Added time of assembly and usage to user description.
• Assembly: Nice clear labeled image of stand and mic.
  • Why, thank you.
• Mechanical Function: Clear explanation. For mic it is described that the diaphragm "causes air molecules underneath it to vibrate. These in turn push down on the magnet that is surrounded by coils of wire." Is it really true that the diaphragm is not physically connected to the coil of the magnet? If so, how is the magnet suspended? Isn't the mass of the magnet too great to respond to high frequency air vibration? Your diagram seems to show a coil attached to the diaphragm that moves past a stationary magnet. Please revisit this and provide an updated explanation with picture or diagram if necessary.
  • There are in fact stationary coil-moving magnet components as well, however after revisiting our product based on your observation we realized that our microphone was a stationary magnet-moving coil. Appropriate changes were made to the report
• Mechanical Analysis: The client does not read MATLAB code so please include your equations using standard mathematical notation, defining your specific notation. If you want to include code it should be standard pseudo-code (although MATLAB-specific code could also be included with the pseudo-code). Any MATLAB functions that represent some more complicated numerical method should be briefly explained instead of just mentioned.
  • The Matlab code was removed from the main text and added to the appendix.

Formatting your lists as lists instead of as paragraphs would make the report easier to read.

• • You seem to say in different places that the number of coils is either 50 or 10, so please clarify.
    • It was in fact 50 coils. Made the necessary corrections.
  • What do you mean when you say that formula used to find generated emf was "crude"?
    • Finding the emf generated is no longer the aim of the experiment and this comment was removed.
  • How do you set SPL = 0.6Pa, b=2e-5 for air? Cite sources.
    • The link to the sources were added
  • How do you know k = 50 N/m for this diaphragm? Is it linear? Is it consistent with material and geometry assumptions?
    • The link to the source had already been provided. As noted in the main text, Samson Audio was unable to give us specific details on the tension applied to the diaphragm within the microphone. This link was the only one available that provided some insight into possible numerical value of tension applied to the diaphragm. Tension applied to the diaphragm is probably decided by method of manufacture of diaphragm. That is proprietary information.
  • It appears G is a function that is zero for all t except t=1, so this is an impulse with a length of time = 0. Matlab will not be able to resolve this and will likely approximate it as an impulse with a time length equal to deltaX, the step size of the simulation. Thus your input depends on the simulation parameters - not good. Should define a well-defined input pulse to get a meaningful response.
    • As suggested in the next point, we removed this part of the analysis and replaced it with a Bode plot of the frequency response.
  • Why not examine a Bode plot instead? More revealing of response characteristics.
    • We acted on this suggestion and agree that the Bode plot was more revealing
  • The two graphs provided do not have axes labeled or time steps specified - difficult to interpret. Table is not clear.
    • Those graphs are no longer part of the revised analysis
• Bill of Materials: Good list. Why is casting and machining listed for one of the plastic parts? Please clarify.
  • Mistake has been fixed. Plastic part is made from molding.
• DFMA: Good observations about material and manufacturing choices. Do you have any comments on DFMA guidelines that were or could have been followed?
• FMEA: Your FMEA conclusions seem to contradict the failure you observed with the soldering. Please reconcile.
  • Soldering failure rate fixed to reflect failure more accurately. Added feedback failure mode.
• DFE: If a CO2 tax were passed, causing electricity prices to increase, presumably these cost increases would be passed to the industries purchasing electricity, so expenses associated with the full carbon emissions in the supply chain would be relevant to the product. Please give us an estimate of how much this might add to the life cost of the product. You also did not comment on emissions associated with production vs. use.
  • Production vs Use table has been added. CO2 tax costs has also been calculated and added to Greenhouse gases section.
• If any of your images, figures, or text were taken from another source, please be certain to provide proper attribution.
  • Added citations in references section.