Audio Expertise for
Telecommunications, Digital and Wireless engineers often add
voice to their design. It has been proven many times that sound quality depends on designer's approach & skills -
and each product sounds differently. Correct conversion of digital signals into analog and sound signals requires a set of critical skills, to ensure high voice quality in the entire chain, end to end,
under all conditions and with all settings of software controls.
Audio Scientific provides this critical set of skills. We take care of all aspects of client design from dBm0 to dBV and dB SPL. We specialize in
audio for telecom, wireless, digital, medical and hand portable products. We
Bluetooth, cellular phones, cordless, telephone handsets,
hands - free, headsets, speakerphones with a variety of accessories, echo cancellers, portable audio appliances,
electronic book readers, noise canceling microphones plus all products where a chain of sound, analog and digital signals involved or voice capability required.
Experience how easy and stress free will be your job when we take care of the
analog end and acoustics. Do not slow down your engineers with audio &
acoustical tasks, delegate such tasks to Audio Scientific! Let Audio Scientific
expertise in analog design and acoustics work for you. Let us shorten your
design time, save you money and faster move your product to market. Compare
voice & sound quality before and after we worked
with you. See Engineering Service Examples
below, Audio Scientific -
Brochure (pdf 508kB),
word doc 65 kB), ask
for a free initial consultation at your location or over the phone, learn about
our Ultra Low Noise Anechoic Chamber,
learn how you can
rent acoustical anechoic chamber on daily basis. Contact Peter Sobczak,
Audio Principal Engineer at firstname.lastname@example.org.
Audio Scientific, 11463 Tree Hollow Lane, San Diego, CA 92128.
Propose a link, report faulty link, send comments to
Acoustics Animations Sound Interactive Demos
Audio Test Equipment
Acoustical Anechoic Chambers
& References Audio Measurement Techniques
Treatment Materials Audio Marketplace
- Ultrasound - Underwater - Wildlife Bluetooth
Audio Circuit Simulators
EMF - Electrosmog
- Schematics & Tutorials
Interesting Sound Websites
Canceling Headphones & Active Hearing Protectors
Reduction & Intelligibility & Voice Quality & Speech
Recognition Ultra High End Devices
Cancellers Suppressors Hands -
Variable Gain Amplifiers
Ultra Low Distortion
Ultra Low Power
Ultra Fast Devices
Acoustics Sound Cards
Audio Companies & Products
Transducers & Headsets
Audio & Telecommunications
Engineering Service Examples
Provide access to our San Diego located sound anechoic chamber. Lease terms
Design appliances with devices like microphones, speakers and buzzers
Conduct Audio Seminars
Setup audio lab at any location of client choice
Hardware Design: dBm0 - dBV - dB SPL - dB Pa
Documentation: Specifications, procedures, design process, manufacturing
Analog Circuit Simulation
Electronic Circuitry Design
Dummy Prototype - product with audio transducers, no electronics
Functioning Prototype - product with audio transducers and electronics
Provide access to our San Diego located sound anechoic chamber
1. Includes power line isolated setup, with all test setup components
powered with individual batteries. We record voice signals down to -3dB SPL "A",
2. Your crew may bring equipment for testing in anechoic chamber and working
on your problem. Our mobile test setup allows automotive tasks like hands-free,
speech recognition, echo canceller, echo return loss, audible noise
Design appliances with devices like microphones, speakers and buzzers
3. Portable audio appliances, laptop, cellular and hands-free phones,
speakerphone and more.
4. Build microphone and speaker into housing including computer monitor
and car interior.
5. All steps from concept to production: Parts selection, documentation,
schematics, drawings, procedures, testing, fixtures, prototypes and calibration
6. Analyze your needs and prepare custom tailored seminar for your
7. General audio, analog circuitry, audio transducers, equipment or
client interest areas presented.
8. Client site or specific case dependent location.
9. Practical tips and answers only audio expert can give.
10. Information about sound nature, sound sources, picking and producing
sound, devices and tricks involved.
11. Problem solving skills at expert depth available on “question and
12. Audio design, circuitry, transducers, parts selection, testing,
troubleshooting, measurement, signal references, sound calibration, test
signals, applying filters, test fixtures and equipment areas.
Setup audio lab at any location of client choice
13. Select anechoic chamber, sound absorbing materials and equipment.
Deal with vendors.
14. Train your crew to use audio test equipment.
15. Design and build specialized test fixtures for general use and
for specific application.
16. Review requirements and prepare detailed list of audio design steps
from concept to production.
17. Evaluate design progress and propose steps needed to speed it up
and move it in right direction.
18. Compare yours and your competitor products in performance and specification
19. Analyze your problem, find what you need and propose detailed action
20. Review schematics, mechanical drawings and audio components?specifications.
21. Review environmental requirement for your product and audio components.
22. Confirm “hearing aid compatibility? “voice recognition compatibility?
“waterproof?and “weatherproof?requirement for product and components.
Hardware Design: dBm0 - dBV - dB SPL
23. Analyze end to end requirement, including mixed signal chips, Codecs,
sensors and audio transducers.
24. Make sure that signals flow properly, following rules.
25. Create requirement for gain, frequency response distribution for
each functioning block in the chain.
26. Specify or evaluate existing circuit interface compatibility with
end devices like speaker, microphone.
27. Create simulation and build devices like loopback fixture, time
delay fixture and more.
28. Digital - Analog - Sound - Microphone & Speaker conversion
29. Specify, select and incorporate semiconductors to meet specific
30. Evaluate, test, troubleshoot and calibrate any portion or entire
existing design, end to end.
31. Extract audio requirement from your documents, industry standards
and customer needs.
32. Create requirement and buying list for requirement for engineering
test equipment with fixtures.
33. Create requirement and buying list for production audio test equipment
and production audio fixtures.
34. Create audio requirement and test procedure for production audio
35. Create audio requirement and test procedure for production audio
36. Create audio requirement and test procedure for product design
37. Create audio requirement and test procedure for product
38. Create level and frequency response limits envelopes, for design
and system verification testing.
Testing and recording
39. Measure and record everything that carries sound or audible frequency
40. Measure and compare yours and your competitor product, specific
segment or end to end.
41. Measure audio transducers like microphones, speakers, ringers,
buzzers, and receivers.
42. Measure directionality, distortion, response, level, noise, tolerance,
echo, sidetone, many more terms.
43. Incoming inspection, qualification and environmental testing, production
troubleshooting, engineering prototypes, vendor samples and more.
44. Sound exposure, correcting test results for noise involved, various
filters and custom-made test signals.
45. Wide range of setup scenario, anechoic chamber to hands-free, from
moving vehicle to flying aircraft.
46. Measure noise created by your product or fixture, evaluate noise
reduction progress, provide detailed comparison charts for each design.
47. Analyze your product and estimate what fixtures are required.
48. Analyze your problem and propose custom design fixture.
49. Fixture design end to end, including mechanics, electronics, transducers
50. Fixtures for testing and troubleshooting circuitry, measuring transducers
and product testing.
51. Fixtures ranging from engineering testing, incoming inspection,
part qualifications and production.
52. Specific problem solving fixtures. Example: Troubleshooting audible
noise, hands-free loopback.
53. Wide range of fixture applications, from high altitude to underwater,
freezing to hot weather, high level electromagnetic noise field to ultra
low level audio signals and more.
54. Translate your product requirement into transducer specifications.
55. Check circuitry compatibility with audio transducers you selected.
56. Evaluate product end to end level and frequency response distribution.
57. Compare and evaluate audio specifications written in different
58. Simulate end to end system for level, response, noise and distortion
59. Create transducers models for accurate simulation of real like
60. Simulate specific problem and specific solution.
61. Simulation files for circuit simulator of your choice.
Electronic Circuit Design
62. Translate product specification into circuitry requirement.
63. Create circuit requirement to match audio transducers.
64. Create requirement for power supply and pc board: Space needed
and design rules.
65. Simulate, analyze and modify existing circuitry, predict and solve
66. Troubleshoot circuitry and propose available solutions, modifications
to meet requirement.
67. Find available on market replacement parts to make your product
68. Find audio components for your application and deal with transducers?
69. Design and build transducers test fixtures for microphone, speaker,
receiver, buzzer, and ringer.
70. Evaluate your audio components per manufacturer or/and your product
71. Evaluate how your audio components stand against another choices.
72. Prepare transducers replacement list.
73. Perform components qualification testing.
74. Select ? Tolerance? “Max Level?and “Min Level?transducers for
75. Evaluate transducers?compatibility with mechanical and electrical
design, per product specification.
76. Analyze mechanics, transducers and electronics level tolerance
77. Analyze mechanics, transducers and electronics frequency response
78. Perform microphones?RF susceptibility testing.
Dummy Prototype - product with audio transducers, no electronics
79. Create ? Tolerance? "Max Level?and “Min Level?prototypes.
80. Evaluate how prototypes stand against product audio specification.
81. Perform preliminary Echo Return Loss test for all prototypes.
82. Assist with pc board layout design.
Functioning Prototype ?product with audio transducers and electronics
83. Create ? Tolerance? “Max Level?and “Min Level?prototypes.
84. Evaluate how prototypes stand against product audio specification.
85. Evaluate pc board design in the audio and transducers areas.
86. Perform preliminary Echo Return Loss and Side Tone tests for all
87. Perform prototypes?RF susceptibility testing.
88. Evaluate prototypes?voice quality with various scenarios.
89. Perform Design Verification Testing. Perform System Verification
90. Assist with pc board layout changes.
91. Select audio transducers for production audio fixtures.
92. Design and build production audio test fixtures.
93. Evaluate and calibrate audio fixtures connected to production testers
with ? Tolerance? “Max Level?and “Min Level?functioning prototypes.
94. Create level and frequency response limits envelopes for production
testers with audio fixtures.
95. Measure 3 production units in audio lab (3 items) and on 3 production
testers (9 items total). Confirm testers?repetition. Calibrate testers?
96. Evaluate production testers?environment, including ambient noise
and RF field.
97. Perform production testers?and production audio fixtures?RF susceptibility.
98. Evaluate testers?results in mass production to ensure proper yield.
Relax testers?envelope if justified.
99. Troubleshoot your product and fixtures to improve manufacturability.
100. Implement Push To Talk PTT feature into your product..
101. Implement Hearing Aid Compatibility HAC into your product.
102. Implement Noise Canceling Microphone or Directional Microphone into
103. Implement Micro Speaker into limited space around your mechanical
104. Reduce Audible Noise in your product.
105. Reduce Echo - improve
echo return loss in your product.
Audio Seminar 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
4. Tolerance mask: Do you specify Fixed Mask or Floating Mask?
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
8. B&K? Audio Precision? ...? Which analyzer is best for you?
9. B&K? ? ...? Which reference microphones are best for
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
13. Why ringer sound testing with high end sound meter can be a very
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 acoustical noise cancellation, electrical noise cancellation, simulations.
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?
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
25. Why generic test fixture will not allow checking your audio part
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
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.
42. When and why “A?filter is a must, test detail not present on many
43. My product does not meet requirement unless I turn off “A?
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
47. How to test puff effect. Test fixture for good repetition.
48. Specific cases when puff effect can be eliminated with high pass
49. Nature of puff effect. Can DSP fix poorly designed microphone
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
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
58. Can noise canceling microphone have rear port more sensitive than
59. How to modify Front to Rear port levels ratio with weather proof
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
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
65. Can 6 mm condenser electret microphone work well for speech
66. Rare applications when 6 mm and 10 mm microphones work equally
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
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.
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
83. How soldering operation can ruin level tolerance build-up
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?
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
99. Can you use pink noise for Bluetooth audio measurements?
100. Should you be concerned about handset echo when working on Bluetooth
101. How do you prepare voice quality test setup for Bluetooth audio?
102. Should you expect updated, completed Bluetooth audio specifications
103. How long it takes to implement Hearing Aid Compatibility - HAC into
104. How do you check if your product is Hearing Aid Compatible - HAC?
105. Where to start when implementing Hearing Aid Compatibility HAC.
106. Should you be concerned about handset side tone (sidetone) when working on
Hearing Aid Compatibility - HAC?
107. The difference between meeting Hearing Aid Compatibility - HAC and
fully meeting Hearing Aid Compatibility - HAC.
108. How to resolve challenges with interpretation of Hearing Aid
Compatibility Standard - HAC Standard.
109. How to resolve challenges around equalization for various
measurements for Hearing Aid Compatibility - HAC.
110. Can different probes be used for various measurements related to
Hearing Aid Compatibility - HAC?
111. How to calibrate Hearing Aid Compatibility - HAC probes.
112. Can Radial and Axial HAC probes be used at a time? Can they affect
113. Can presence of HAC probes affect magnetic field? Can it be
compensated? Would such compensation always work?
114. Hearing Aid Compatibility - HAC compliance per various software
settings across entire volume control range.
115. How to calibrate Hearing Aid Compatibility - HAC probes.
116. Build your probes for Hearing Aid Compatibility - HAC or purchase
117. Accuracy of various Hearing Aid Compatibility - HAC measurements.
118. How to resolve component tolerances against requirements for Hearing
Aid Compatibility - HAC.
119. How to resolve temperature changes around HAC coil.
120. What products may require Hearing Aid Compatibility - HAC, presently
and in the future.
121. Health issues around magnetic field associated with audio path of
Hearing Aid Compatibility - HAC.
122. How to resolve power consumption issues in Hearing Aid Compatibility
- HAC design.
123. Hearing Aid Compatibility design with Bluetooth.
124. Axial and Radial components of Hearing Aid Compatibility - HAC.
125. Can audio and RF portions of Hearing Aid Compatibility - HAC be met
at different spots and still meet overall requirement?
126. Fulfilling Hearing Aid Compatibility - HAC - listening test per
specification. Practical valuation criteria and required measurements.
127. Differences between passive and active probes for Hearing Aid
Compatibility - HAC measurements.
128. Where active probes shine and where passive probes are a must.
What you need is not listed here? Write to Peter Sobczak at
Cellular Phone - Performance Evaluation, test results shown in table
Cellular Phone - Side Tone Test, plots shown with side tone weighting
Cellular Phone - Receiver Frequency Response Test, plots shown before and
after circuit redesigned.
Cellular Phone - Echo Return Loss Test, plots shown with ERL weighting
Condenser Electret Microphone Cartridges, Self Noise Comparison Test - 3
different models & vendors