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Audio  Questions
1.    AC coupling capacitors: Coupling frequency corner per design's frequency corner. Differential input coupling.
2.    AC coupling capacitors tolerance and final CMRR. How 80 dB CMRR turns into below 30 dB.
3.    Why test results may not fit tolerance mask, yet tested object is fine.
4.    Tolerance mask: Do you specify Fixed Mask or Floating Mask? Mask types.
5.    Why tolerance masks for production tester and product specification are different.
6.    Why sine sweep belongs to the past in the audio testing area - level and noise dependent response, level dependent noise floor, a lot of  DSP, steady tone seen as noise or whistle signal to mute. When sine sweep is the best way to go.
7.    Why today high end audio analyzers may not tell the truth (calibration, repetition, side effects, test signal does not fit specific scenario).
8.    B&K? Audio Precision? ...? Which analyzer is best for you? Why?
9.    B&K? …? ...?  Which reference microphones are best for you? Why?
10.  Why would I spend hundred dollars for microphone calibration when my microphone works fine?
11.  B&K sound meter? Why? Which sound meter is right for you? What is type 1 and type 2?
12.  Sound meters design flaws their manufactures do not want you to know.
13.  Why ringer sound testing with high end sound meter can be a very bad mistake.
14.  Do you properly select audio transducers for your application? Microphone? Receiver? Buzzer? Ringer? Speaker? Why your transducer may not be selected properly while it works OK in your product?
15.  How do you select noise canceling microphone for your application? Common mistakes in microphone selection and noise cancellation estimate.
16.  What really is that “noise canceling effect”? End to end components of noise cancellation.
17.  Test techniques for noise canceling microphone: Level, frequency response, directionality, cancellation effect.
18.  How do you test your product with noise canceling microphone? Many speakers around? Frequency response at 0 deg & at 1"/2' or polar pattern? Best test strategy for your application.
19. Can your microphone cancel noise up to average 15 dB? Explaining myth about “average 15 dB noise canceling effect”.
20.  Why each test technique brings different results and how to compare such different results.
21.  When  “average” can substitute “nominal” for audio transducers? Common misconceptions.
22.  Do you have realistic expectation for audio transducer testing for production troubleshooting?
23.  Why software can adjust microphone nominal level only in some cases?
24.  How you can change transducer level when no access to circuitry available.
25.  Why generic test fixture will not allow checking your audio part specification accurately.
26.  Environmental concern – can you buy microphone for 90 deg C storage and 65 deg C operation?
27.  Why should you care about weatherproof screen for audio transducers.
28.  Weatherproof or Waterproof? Are your audio transducers meeting first or second requirement?
29.  Can weatherproof screen change frequency response or acoustical echo for your product?
30.  Ringer's volume control. Ringer playing tunes. How do you turn volume down?
31.  My ringer is too quiet and I have 1 week left. Can extension tube solve my problem?
32.  Micropower operational amplifiers for audio – mistakes with insufficient slew rate (Band, CMRR).
33.  Why engineering prototypes meet requirement yet production yield will be poor.
34.  You confirmed good echo performance in hands-free mode and complaints are coming. What do you do?
35.  Do you avoid audio transducers from vendors with unknown reputation? Do you have peace of mind when buying more expensive microphone?
36.  Is custom made coupler from manufacturer a must for receiver transducer testing?
37.  Does noise from Signal to Noise Ratio (SNR) substitute noise from Noise Floor measurement? When?
38.  Can I test ringer sound of 2 kHz with 5 kHz analyzer? Yes if…
39.  Techniques to control ringer output level and associated problems.
40.  When ringer meets requirement but only at 0 deg...
41.  Hard drive noise attenuating enclosure does not work as expected. Why?
42.  When and why “A” filter is a must, test detail not present on many specifications.
43.  My  product does not meet requirement unless I turn off “A” filter…
44.  What are A, B, C, G, U, AU filters?
45.  My cellular phone meets specification but does not sound right. What do I do?
46.  Why puff (not pop) effect may ruin performance of otherwise well designed microphone.
47.  How to test puff effect. Test fixture for good repetition.
48.  Specific cases when puff effect can be eliminated with high pass filter.
49.  Nature of puff effect. Can DSP fix poorly designed microphone housing?
50.  Why side tone does not always indicate puff effect.
51.  When puff effect can degrade performance in hands free mode.
52.  Why 99% phones on market have puff effect and some are simple very bad.
53.  Which microphones exhibit best and worst puff effect and why.
54.  Puff effect and microphone directionality.
55.  Puff effect per weather proof screen in case when noise canceling microphone has two ports.
56.  Directional microphone designed for small enclosures.
57.  Can cardioid microphone be made from noise canceling microphone cartridge?
58.  Can noise canceling microphone have rear port more sensitive than front port?
59.  How to modify Front to Rear port levels ratio with weather proof screen.
60.  Weatherproof screen per frequency response and polar pattern. Can they be entirely independent?
61.  Directional microphones with two cartridges. Advantages and disadvantages. Design trade-offs.
62.  Can microphone cartridge be selected properly with no requirement prepared earlier?
63.  When microphone cartridge can be a source of customer complaints after production cranks zillions...
64.  Common mistake with ignoring microphone self noise and why.
65.  Can 6 mm condenser electret microphone match performance of 10 mm microphone?
65.  Can 6 mm condenser electret microphone work well for speech recognition?
66.  Rare applications when 6 mm and 10 mm microphones work equally well.
67.  Spring contacts or flex circuit? How do they compare from microphone performance stand point.
68.  Possible horror scenarios for spring contacts, flex circuit and soldered wire connections.
69.  Can anyone solder microphone cartridges? Why not? Two horror stories and how to avoid them.
70.  Microphone housing: Hard rubber? Soft rubber? How do you tell which one performs better?
71.  Maximum sound that condenser electret microphones can handle. Factors limiting high level signal.
72.  Which microphones accept high level best and worst. Can you define highest sound level for your design?
73.  Can you influence microphone maximum level? Do you do it without knowing?
74.  Condenser electret microphone load. What is behind supply voltage range and load impedance.
75.  Can I use active load for condenser electret microphone? Cases when YES applies.
76.  Bipolar transistor acting as simulated inductance for condenser electret microphone load.
77.  Can microphone load be utilized as frequency response network? Trade-offs and dangers here.
78.  Differential input connected to electret microphone cartridge. Common misconceptions.
79.  What is memory effect for electret condenser microphone cartridge? How to improve production yield for level testing.
80.  Are condenser electret microphone electrostatic sensitive, when Source - Drain contacts have 1 kOhm connection? Why are microphones recommended to handle with static protection?
81.  If static damages microphone cartridges, why are they shipped without proper electrostatic protection?
82.  Can soldering iron without static protection damage microphone cartridge?
83.  How soldering operation can ruin level tolerance build-up calculations.
84.  Full list of level tolerances for every microphone project,  from microphone housing to amplifier output.
85.  Can level tolerance build-up calculations substitute frequency response tolerance build-up?
86.  Can frequency response for specific microphone element change because of microphone handling in production?
87.  Speakerphone acoustical testing scenarios and best reference microphones for each scenario.
88.  Test setup for speakerphone acoustical testing.
89.  Evolution of test signal for speakerphone testing. How do you design test signal for finding speakerphone side effects?
90.  Can voice quality be assessed properly with ONE working prototype? When?
91.  What factors to include when assessing voice quality for your product.
92.  Is voice quality fixed for your product or is it varying with time? How to check, predict.
93.  How to find voice quality problem source & differentiate voice quality between entire system per your product, product per audio transducers.
94.  How poor echo or side tone can make voice quality worse.
95.  Is voice quality fixed for your product or is it varying with time? How to check, predict.
96.  How do you determine Bluetooth protection level on Receive path?
97.  Can Bluetooth audio gain distribution be different between products?
98.  How do you measure Bluetooth loudness rating on Receive and Transmit path?
99.  Can you use pink noise for Bluetooth audio measurements?
100.  Should you be concerned about handset echo when working on Bluetooth audio compatibility?
101.  How do you prepare voice quality test setup for Bluetooth audio?
102.  Should you expect updated, completed Bluetooth audio specifications coming soon?