Prior Accomplishments and Service Examples for Audio Scientific, San Diego, CA
Audio Scientific is an independent consulting company, serving cellular phones, wireless, portables and telecom companies. Our experience covers over 30 years in the field of electronics, including audio transducers (microphones, speakers, receivers, ringers, buzzers), acoustics, analog & micropower circuit design, voice quality with projects for companies worldwide.
Our lab is fully equipped to deal with almost any technical, audio related problem. We have built a long line of custom designed fixtures, allowing wide range of repetitive tasks requiring very special acoustical accommodations. We perform tasks covering 0.1Hz to 200kHz frequency band and signals well below -3dBSPL”A”. Our ultra low noise, RF shielded Anechoic Chamber allows unique applications with its ambient noise of -55dBSPL”A”. We work on small projects like speaker, microphone implementation and larger projects from concept to production.
and Service Examples for Audio Scientific, San Diego, CA -
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Professional Experience for Peter Sobczak, Audio Scientific, San Diego, CA
3-2013 to 2-2018 COUNTRYMAN ASSOCIATES, INC. Menlo Park,
· Responsibilities included new product design, current products support, and production support.
· Designed micro power analog circuitry for various miniature microphones. Includes opamp based, transistor based and mixed analog circuitry. Simulated circuitry, worked on PCB layout design.
· Improved existing products for better RF immunity, better dynamic range and better compatibility with multiple interfaces.
· Improved measurements techniques for engineering and production stations. Simple, cheap solutions allowed building at will many inexpensive test stations.
· Built a line of simple and more complex Test Fixtures for more accurate, faster and simpler manufacturing process. Examples - 0.1dB precise MIC sorting for 1kHz level - 0.2dB precise MIC pairing for frequency response - XLR microphone check for polar pattern in various production phases - PCB noise testing for detecting low level noise on board.
· Rebuilt Polar Plot test setup. Resulting improvements were dramatic and allowed improvements for company’s flagship microphone with dual capsules.
· Created a new technique for microphone RESP testing with instant distance adjustment capability. This allowed accurate RESP within distance range ˝” to 18” on small benches and easy, inexpensive duplicating such setup.
· Analyzed existing products requirement, translated them into requirements for individual components, assisted a team when multiple part models available, part turned obsolete or different part allowed better product performance.
· Investigated, troubleshot microphones with borderline performance, special cases for customer returns and special / custom builds. Included noise, polar pattern, inconsistent level, uneven Frequency Response, unusual DC voltages, insufficient maximum signal.
· Built a long line of microphone powering boxes to allow microphone testing per conditions equal to specific interfaces and Beltpack Transmitters.
· Built entirely new Microphone Noise Testing Station with simple criteria covering full line of microphones, PCBs.
· Analyzed customer requirements for custom microphone connections. Created custom microphone wiring diagrams to allow microphone compatibility with more than one Beltpack Transmitter. Or to allow more than one microphone working with given transmitter.
· Worked toward newer technology on production benches, searched for better tools and setups. Examples: Ultra quiet fans cut dramatically on audible noise level on benches, allowing cleaner acoustical test data. Prepared conditions for transition to 0201 parts with introduction of Ultra Thin Soldering Tips, Ultra Thin Desoldering Tweezers Tips, Ultra Thin Cobaltima Tweezers.
1-2008 to 2-2011 LAB126 - AMAZON
Audio Engineer - Contract
· Worked in full range of Kindle design activities, analog circuitry, acoustics, guided PCB layout design.
· Analyzed older Kindle model toward achievable audio improvements, worked on a line of new Kindle models.
· Wide range of measurements covering full performance of Headphones, Microphones, Hands-Free Speakers.
· Supported production in aspects like troubleshooting of distorting speakers, test fixtures.
1-2006 to 12-2007 PALM
Audio Engineer - Contract
· Supported Audio Team in full range of Smart Phone design activities, analog circuitry, acoustics.
· Headed Hearing Aid Compatibility HAC development. Implemented various solutions into Smart Phones, designed, and built instrumentation and fixtures allowing early estimates for HAC compliance.
· Analyzed various aspects of Speaker, Ear, Microphone, Vibrator transducers performance within Smart Phone enclosure. Created performance criteria and Reference documents.
· Created Audio Reference documentation covering multiple Audio projects.
2002-2005 NOKIA MOBILE PHONES San Diego, CA
Senior Design Engineer
· Responsible for developing audio – acoustics in cell phones through all stages from concept to production.
· Headed HAC - Hearing Aid Compatibility development in cell phones. Developed a line of solutions in order to achieve HAC compatible cell phone. Participated in HAC standard development. Analyzed audio requirements, directed HAC component development, designed HAC audio circuitry and guided associated PCB layout, developed and built a line of passive and active test fixtures and probes, developed detailed test procedures for engineering, high volume production and Product Evaluation Groups. Design efforts focused on component and product miniaturization while maximizing audio signal quality. All HAC support related to very high volume manufacturing and components development.
· Studied all aspects of implementing Class-D amplifier into CDMA cell phone. Considered aspects affecting audio signal quality like RF emissions, various feedback signals through battery system, PCB layout, filtering and shielding techniques in cell phones.
· Participated in evaluation, developing requirements and testing techniques for integrated circuits containing RF filters and ESD filters on audio signal path.
· Tested audio and audio & RF performance of cellular phones, focusing on standard conformance and sound quality.
· Evaluated audio performance of cell phones related to various settings of SW based audio controls and audio DSP enhancements. Worked with a line of Codecs, A/D and D/A solutions in cell phones.
· Implemented a line of acoustical solutions for Ear speaker and Hands-Free micro-speaker acoustics in cell phones with ultra small space, simulated of acoustics and analog circuitry, designed matching audio circuitry, evaluated end to end audio signal quality, built and evaluated SLA prototypes with micro speakers and microphones, created associated documentation like detailed test procedures, test reports, component requirements and more.
· Resolved many electrical & acoustical echo/feedback problems related to audio design with micro acoustics and analog circuitry sharing space with digital/RF solutions.
· Headed PTT “Push To Talk” Speaker development in cell phones. Designed and built test equipment and fixtures for evaluating components, solutions & entire product.
· Provided guidance to DSP, Baseband, Mechanical, System Design, Product and Production Testing teams.
· Evaluated a line of audio components & miniaturized solutions for all performance aspects including lowest and largest signals, extreme environmental operating conditions and stress, RF - immunity and susceptibility, conducted & radiated, various supply schemes, gain distribution schemes, full audio & mechanical compatibility with associated external attachments & accessories, very high volume manufacturing & planning. Participated in inspection of overseas plants and more.
1993-1999 HUGHES NETWORK SYSTEMS San Diego, CA
Audio Principal Engineer
· Provided expertise in audio, acoustics and analog circuitry. Coordinated design and analysis of electro & acoustical products for automotive, cellular and wireless applications from concept to production.
· Provided guidance to DSP, Baseband, Mechanical and Production Testing teams.
· Specialized in noise canceling technology, including microphone transducer with housing and corresponding circuitry.
· Invented test procedure for finding acoustical isolation between microphone and receiver paths which allowed predicting echo number in advance, at the early stage of phone design. It tremendously reduced tooling costs, shortened design time and allowed obtaining patent for improved microphone boot design.
· Redesigned complex circuitry and acoustics for variety of cellular phones and telephone systems in order to enhance sound performance and to meet specifications.
· Reorganized and rebuilt Audio Lab due to required higher capacity. Introduced innovative testing procedures with custom designed fixtures, which allowed obtaining virtually all test results and sound quality information from a single, quick test.
· Developed accurate, truly noise-free technique of recording analog and digital telephone line signals for voice quality evaluation.
· Designed and built a line of fixtures for audio lab and production testing, focusing on test accuracy, reliability, simplicity, minimum noise pickup and easy of use.
· Evaluated speech recognition in many vehicles. Investigated relations between vehicle size, shape, and interior design per microphone, speaker frequency response, and level in hands-free mode.
· Invented test process for remotely evaluating acoustical properties of all types and sizes of vehicles by making a hands-free phone call with custom made test signals.
· Investigated various omni-directional, uni-directional, bi-directional and second order microphones in hands-free mode for best location in a car. Focused on voice quality, ambient noise and vibration pick up.
· Wrote audio documents with requirement and test procedures for design verification, system verification, production, transducers, dispatch speaker, vehicle hands-free, speakerphone, echo canceller and more.
· Developed simulation models for audio transducers including noise cancellation microphone cartridges.
· Reviewed available on 1998 market ringers, noise canceling microphones and leak insensitive receivers for low voltage and small enclosure cellular phones.
· Designed two wire circuit for active microphone that provided twice more signal swing compared to competitors microphones signal swing.
· Routinely solved audio and telephone design problems at both the circuit level and the system level, exploring concepts like ROLR, TOLR, DORL, ERL, sidetones and isolation.
· Analyzed and troubleshot end to end systems consisting of sound - transducer - amplifier - A/D converter - transmit - loopback - receive - D/A converter - amplifier - transducer - sound. Calculated conversions between dBmo, dBV, dB SPL with distribution of level, gain, noise, signal swing and frequency response.
· Extracted audio specs from standards like TIA-579, TIA-IS-85, IS-55, IS-56, IEEE-661, IEEE-269, ETS 300 and documents for CDMA, TDMA, GSM and more.
1989-1993 SHURE BROTHERS, INC. Evanston, IL
Senior Design and Development Engineer
· Designed and developed electroacoustical products for noise canceling, wireless, automotive, voice recognition, teleconferencing, medical electronics and aircraft applications. Design included analog and some digital circuitry focusing on cost, reliability, power management and manufacturability. Proficient in SPICE design simulation. Created documentation and specifications based on customer requirement.
· Participated in numerous projects simultaneously going into production.
· Designed first FAA approved DTMF microphone with lighted keypad for aircraft industry.
· Designed universal noise canceling telephone handset which meets all requirements for Motorola, AT&T and RCA.
· Designed and built noise canceling telephone handset with two omni-directional cartridges providing a 15 dB average canceling effect.
· Designed a $0.50 micropower amplifier working below 0.6 Vdc.
· Designed micropower (2 Vdc, 100 uA), wide-band, 90 us delay circuit to compensate phase shift between two bidirectional cartridges.
· Designed current source amplifier allowing ten microphones to operate with a common load without mixer.
· Designed high temperature circuit for vibration canceling unit of two ceramic sensors. Stabilized sensitivity to within +/-3 dB while exposed to temperatures within -40 to +150 C.
· Designed and built active resonance circuit amplifier with simulated inductance for quadropole microphone in reflecting surface environment.
· Designed and built auto response circuit modifying frequency response of automotive microphone depending upon audio or noise level.
· Designed adjustable frequency response circuit eliminated rejections and expensive repairs.
· Designed and built test fixture to test small DCR changes in AC coupled circuits. It replaced less sensitive impedance meter.
· Designed a $1.20 circuit that matched balanced inputs with non-balanced sources. It solved hum pickup problem and replaced a $5.50 amplifier plus matching transformer.
· Designed and built a test fixture to check transformer shield can quality. Developed electromagnetic hum pickup standard and test procedure.
· Reviewed company products and set requirement for replacement parts including all potentiometers (new vendor), resistors (unification) and condenser microphone cartridges. Redesigned production circuits eliminating germanium transistors/diodes.
· Located and removed response variation source in production mixer. Changed PC board layout and dressed wires.
· Set standard for radio frequency interference test simplifying procedures.
1988-1989 J. B. ELECTRONIC TRANSFORMERS Chicago, IL
Electronic Lab Technician
· Tested and evaluated production and engineering samples of inductive devices. Work involved phase shift, insulation resistance, turns ratio, self - resonance and saturation frequency testing. Assisted engineers in development and design of devices.
1987-1988 NICOLET INSTRUMENT CORPORATION Madison, WI
· Tested, calibrated and repaired electronic biomedical equipment to component level.
· Designed hand held headphone transducer test fixture, reducing polarity and continuity check time from five minutes to five seconds. It replaced entire bench consisting of oscilloscope, reference microphone and signal generator, which bench allowed only polarity check.
· Eliminated noise from a Compact Console speaker, using complex troubleshooting technique and math.
· Designed hand held test fixture detecting and recognizing polarity of acoustic pulses.
1982-1986 DIORA Dzierzoniow, Poland
· Designed analog and digital circuits for home entertainment products including low noise audio and RF circuits.
10-1999 to present DBA AUDIO SCIENTIFIC San Diego, CA
§ Stays on the top of newest audio technology, including latest microphones, speakers, audio ICs, ultra low noise & ultra low power devices.
§ Assisted all audio design aspects for Electronic Book Reader – multiple Kindle models at Amazon, Cupertino. Implemented Speakers, MEMS and Condenser Electret Microphones with corresponding acoustics, Text – to – Speech, various audio test and audio evaluation techniques.
§ Assisted all audio design aspects for Smart Phones at Palm, Sunnyvale. Headed HAC – Hearing Aid Compatibility development in Smart Phones.
§ Developed test technique and test instrumentation for testing Infrasonic Microphones below 0.1Hz. Cut infrasound microphone Frequency Response measurement time down to 30seconds.
§ Analyzed Bluetooth specifications from voice quality, interface compatibility and audio compliance stand point. Based on various industrial standards, created a set of audio specifications, far more detailed than Bluetooth general audio specifications. Focused on matching Bluetooth chip interface with various Codecs, various handsets & hands-free scenarios.
§ Built test fixtures for measuring audible part of Hearing Aid Compatibility at component and product level.
§ Tested audio and audio & RF performance of cellular phones, focusing on standard conformance and sound quality. Incorporated voice feature into portable, wireless modem.
§ Provided audio assistance to Wireless Local Loop, GSM product. Designed and built a line of active and passive interfaces for measurements in engineering lab and in high volume production. Supported design team in aspects of RF related audible noise, PCB layout, evaluated end to end electrical & acoustical echo, created audio specifications and procedures, evaluated and specified audio requirements for analog circuitry, components, Codecs, telephone line interfaces and ESD protecting devices.
§ Set up audio lab, based on anechoic chamber and sound analyzer, capable of virtually every audio related task, from ultra high quality sound recording and device evaluation to cellular phone testing.
§ Designed and built a line of fixtures for accurate and repeatable measurement of audio transducers and cellular phones.
§ Invented phone echo measurement technique with a phone call and custom designed test signal, allowing phone echo test without base station.
§ Invented noise-canceling microphone with Flat Frequency Response and ultra low noise of 12 dB SPL. It provides high quality sound recording in presence of high level ambient noise.
§ Designed complex test signal for testing highly non-linear devices with extensive signal processing. Primarily used for cellular phone testing with frequency response and SNR varying with signal level.
§ Designed and built personal communicator that triggers audible alarm when ambient noise exceeds preset level. It consists of a 1 uA, 2.5 Vdc, 100 dB gain amplifier circuit, allowing one dynamic transducer acting as microphone and speaker at a time.
Large value microphone
does not work properly with one of Beltpack Transmitters. RF immunity for
microphone is questioned, but no known RF filtering techniques reduce audible
noise from microphone. Shipping microphone to customers is put on hold. All
testing indicates excessive noise, but microphone alone is fine, works with long
line of other transmitter models. Critical Beltpack transmitter also works fine
with many other microphone models. Noise analysis indicates transmitter might be
producing noise itself on supply voltage pin. Adding RC filter to supply voltage
pin restored microphone performance.
WROCLAW POLYTECHNIC INSTITUTE, Wroclaw, Poland Master of Science: Electronics, 1980 Major: Electronic Acoustics
WROCLAW POLYTECHNIC INSTITUTE, Wroclaw, Poland Bachelor of Science: Electronics, 1978
· In 1997 completed Bruel & Kjaer Seminar "Electroacoustic Measurements on Telephones"
· In 1995 conducted Engineering Seminar "Microphone Cartridges & Noise Cancellation Techniques"
ADDENDUM - ADDITIONAL DESIGN ACCOMPLISHMENTS
· Circuit for precision DCR test of powered transformers.
· Circuit to test eight transformer parameters simultaneously. Reduced test time sixty times and eliminated error sources.
· Ultrasound distance meter with precision compensation of sound speed variables.
· Circuit to switch between sensors in a car from telephone keypad.
· Test fixture for phase mismatch of two sound sources.
· Evaluated shielded cables for shield resistance noise, shield capacitance noise, shield vibration noise, shield protection against hum and RF field.
· Circuit to detect microphone presence at one of many inputs, that automatically activated right signal path.
· RF Booster audio circuitry providing high CMRR for fax signal.
· Hand held probe with ultra low noise circuitry to measure low level signals across capacitors.
· Ultra low noise preamplifier to boost level of B&K microphones and allow recording of very quiet sounds.
· Various fixtures for measurement of noise canceling microphones on the flying airplane. Measured on the airplane variety of telephone handsets with different microphone model and polar pattern each one.
· Telephone handset consisting cardioid microphone and dispatch speaker.
· Simulated, redesigned circuitry and measured level, frequency response to unify many telephone systems, platforms for various vehicles and various microphones.
· Evaluated various telephone handsets from many countries in order to select the best handset for newly designed satellite system.
· Measuring setup for DSP group to allow audio performance evaluation for DSP solutions.
· Recommended audio solutions and interface circuit detail to be required and incorporated into future micropower Codec chips.
· Test technique, fixtures for quick evaluation of acoustical resistance, wind, dirt and water screen materials.
· Test technique, fixtures for level, frequency response repetition of ringers, speakers and microphones.
MISSION CRITICAL PROJECTS
· Cellular phone entering production distorted sound under certain conditions. Various teams investigated distortion for weeks with no success. Solution: In a few hours found that piezzo speaker distorted only when high level combined with certain words. Replaced speaker with another model and distortion stopped.
· Production phone with poor yield had no access to audio signals. Various attempts to troubleshoot rejected phones failed and finally production stopped. Solution: Within 2 days designed and built a fixture acting as reference phone with zero tolerances. Testers checked level by comparing phones to reference phone and production continued.
· Engineering samples of hand held, noise canceling microphone sounded different each one and customer could not place an order. Solution: Within hours found varying quality of acoustical screen in front of microphone port. Selected right screen material to fix a problem. Customer placed an order and microphone went to production.
· Customer reported echo from production phone. Solution: Investigated the phone, within hours found microphone housing weakness and proposed to increase microphone port size, thus increasing sound level and boosting signal to echo ratio. Improvement satisfied customer and more orders followed.
· Customer reported echo problem with telephone handset entering production. Solution: Immediately found electrical echo signal developed across handset cable resistance. Proposed adding spare wire to active wire, reducing resistance on signal path and lowering echo signal to satisfying level. It allowed design team meet schedule and cost.
· Satellite System designed to support election overseas could not be shipped due to blowing fuses during power up. Design team could not fix a problem with 48 hours left. Solution: Analyzed schematic diagram. Immediately found that FET input capacitance was not included into charge scheme during powerup time. Proposed new values for near resistors and capacitors to fix a problem. Within 4 hours a few units were modified, checked and ready to ship.
· Docking Station for automotive phone generated variety of audible noise, design team worked months with no success. Solution: Modified circuit gain distribution, changed op amps bias circuitry and interface configuration. Eliminated all noise within a week, and design team met projected budget plus schedule.
· Dual Mode Phone generated audible noise, detected just before scheduled production. Solution: Immediately located noise source, modified pc board layout, op amps bias circuitry and phone interface circuitry. Noise went down to acceptable level, allowing the phone enter production.
· Marketing changed transmit response requirement for telephone handset entering production, with expected redesign & retooling time a month. Solution: Immediately investigated a problem and proposed new shape microphone port. Existing tooling required only minimal modification and the handset met tight schedule.
· Telephone Handset production could not move to Mexico due to poor production yield. Solution: Immediately found that vendor unsoldered microphone pads to remove solder, creating holes on microphone back and distorting frequency response plus level. Offered new procedure for vendor that fixed a problem.
· Cellular phone with dispatch speaker caused distortion when its speaker sounded loud. Radio frequency reference device vibrated from speaker sound and modulated RF signal, thus causing distortion. Solution: Investigated vibration spectrum. Immediately developed custom test signal for speaker. RF team used such signal as the only troubleshooting technique available to compare various solutions and make design decisions resulting in distortion free phone.