Frequently Asked Questions

Microphones & Acoustics

Get your most commonly asked acoustics questions answered.

Section I: Definitions and Terminology
Section II: Microphone Recommendations
Section III: Calibration and Testing
Section IV: Specification Clarifications
Section V: Specialty Microphone Applications
Section VI: Maintenance and Handling

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What are the black protective rubber caps on PCB® microphone/preamplifier systems used for? Where can I view all the PCB® microphone videos? How do I clean a microphone? When can I remove the microphone grid cap? How should I properly care for and handle my microphones? What is Phantom power? How do I estimate what my output voltage will be so that I can set my resolution on my DAQ? What does the phase specification for a microphone represent and how is it used in acoustics applications? If two sound waves are equal in amplitude but opposite in phase what is the net effect? If I add two sound sources together, for example 2 Pa each, what is the net effect on the sound pressure level in decibels? When performing acoustic measurements in a tube, why is it recommended that the wavelength of sound be bigger than the diameter of the open end of the tube? How do I obtain enough constant current for a low noise microphone, if my Data Acquisition System limit is 2 mA? Can I use a microphone designed for one response field, within a different field? And how do I correct for it manually? What is the minimum sound pressure level that a PCB® microphone can measure? Where can I view all the PCB® microphone videos? When should I use a windscreen, and what is the material used? What is NAH and its relationship to ’array’ microphones? I want to flush mount a microphone in a pipe. I understand that problems can arise from improper venting. What consideration should be given to venting and what can be done to prevent improper venting? What is the recommended microphone for wind turbine testing? Can a microphone be flush mounted with the grid cap removed? What is the rise time of PCB® model 377A12 microphone? What should I do if the pad on the water resistant microphone (PCB® model 130A24) gets clogged from contamination or oil? What is the anticipated impact of using a microphone at 6290 ft. above sea level? Does a windscreen affect the sound field and output of the microphone? What is the standard for compliance of working class, test and measurement microphones? Why is the output of my prepolarized microphone 180 degrees out of phase with my externally polarized microphone? How do I estimate what my output voltage will be so that I can set my resolution on my DAQ? How do I obtain enough constant current for a low noise microphone, if my Data Acquisition System limit is 2 mA? What is the minimum sound pressure level that a PCB® microphone can measure? What is the maximum cable length I can use for a PCB® model 377B02 microphone and model 426E01 preamplifier? Will a preamplifier change the sensitivity of a microphone? What is the maximum temperature that microphone and preamplifier system can withstand and how does the heat affect the application? What is the maximum SPL limit of a microphone? How is it specified? Can I use a PCB© microphone beyond its specified frequency range? Does PCB’s model 079A02 adapter for 1/4" microphones to 1/2" preamplifiers affect microphone performance? I have static pressure coefficient for my PCB® microphone preamplifier system but what is the static pressure limit? Can this microphone operate at 40,000 feet? What is the operating temperature of PCB® model 377B02? Why are there two sensitivity specifications on my PCB® microphone calibration certificate? How does a preamplifier impact the dynamic range of microphone? Does increased sound pressure cause a positive or negative voltage at the output terminal? Why do PCB® 130E21, 130E22 and 130A23 array microphone models have different diameters than the 1/4" 378 series microphones. What would cause a difference in results between a PCB® model 130E20 array microphone and a working standard PCB® model 378B02 microphone? Is the temperature coefficient linear beyond the IEC 61094-4 (working class microphone) required limits of -10 °C to +50 °C? What are the temperature coefficient effects of a preamplifier? Should cartridge characteristics be considered or do I need to also consider the temperature response of a preamplifier? Is it safe to use a microphone at its maximum rated temperature? What is the difference between absolute phase and relative phase for condenser microphones? What is the difference between PCB® model 130E22 and model 130A23? What is the minimal sound pressure level (SPL) measurable with a microphone? Where can I view all the PCB® microphone videos? Can a prepolarized ICP® microphone be used with an externally polarized preamplifier and power supply? How does distance affect the sound pressure level? When I receive a PCB© calibration certification with my microphone, can it be used, as is, or do I need to calibrate it at my test site? Is it better to calibrate a microphone and preamplifier separately? Why do the PCB® short preamplifier models, 426A07 and 426A13, have 2 vent holes in them? Can I calibrate PCB® model 378A04 low noise microphone with any handheld calibrator? Do I need an adapter to perform a single point field calibration check on the PCB® model 130B40 surface microphone? What is the importance of the vent hole position in a preamplifier? Will you get the same results (at frequencies < 1 kHz) when you use a free-field random incidence or pressure response microphone? How does distance impact the results for my measurement microphone? Why do I measure a different sensitivity in the field than what is listed on your factory calibration certification? Are the PCB® model 377 series of microphones 100% tested? Will improper grounding negatively impact the noise floor of a microphone? Are drop tests performed on PCB® 377 series microphones? Can calibration corrections be provided for PCB® microphones in an Excel format so software corrections can be done? When measuring sound with test and measurement microphones do I need to be in an anechoic chamber? How often should I calibrate my microphone? Can noise floor calculations be used to discover sources of unwanted noise? What are the recommended microphones for machinery health monitoring? What is Phantom power? What is the maximum cable length that you can use with a test and measurement microphone? Where can I view all the PCB® microphone videos? What is the difference between a PCB® array microphone and PCB’s 377B02 microphone? Both models 130E20 & 377B02 appear to be free-field ICP® microphones with BNC connectors. We previously used low cost vocal music microphones and are looking at upgrading to test and measurement microphones. What are the basic differences and advantages? What are the advantages and disadvantages of a traditional 200V microphone set-up, as compared to the more modern prepolarized design? Which holder is recommended for the 1/4" array and 1/4" working standard for PCB® 378 series of microphones? Which prepolarized microphone is recommended for qualifying an anechoic chamber? Which PCB® prepolarized condenser microphone offers the highest amplitude measuring capability? Is there a prepolarized, cost effective solution to a 1/2" externally polarized low noise microphone? What is the most cost efficient working class pressure microphone for low amplitudes for sounds up to 10 kHz? Can a 1/4" microphone be used with the high temperature, PCB® model ½” HT426E01 or other vendors’ ½” high temperature preamplifier? Does the size of a microphone impact its frequency and dynamic range? What microphone is recommended for determining the direction or noise source location of sound? Which microphone is recommended for low frequency measurements? How do I choose between a 1/4" and 1/2" measurement microphone? In my application, I need a cost effective way to perform sound pressure mapping, beam-forming, holography or noise source location with multiple microphones. How do I do this? I need to take sound pressure measurements in a confined area or a high temperature environment. Which microphone should I use? When should a surface microphone be used? When should prepolarized microphones be used for acoustic testing? What is the maximum cable length that you can use with a test and measurement microphone? What is the standard for compliance of working class, test and measurement microphones? What are octaves? Why is the output of my prepolarized microphone 180 degrees out of phase with my externally polarized microphone? What does the phase specification for a microphone represent and how is it used in acoustics applications? What does it mean for two or more sound sources to be incoherent? What does it mean for two or more sound sources to be coherent? Where can I view all the PCB® microphone videos? What is ICP®? What is the difference between the LEMO® type and the coaxial cables used with test and measurement microphones? What is the difference between a condenser microphone and a piezoelectric pressure sensor? What is A-weighting and what is the best way to implement it? What is an a-weighted filter? What is the rise time of a microphone? What is a polar plot and how is it used? What is the noise floor of a microphone? What are the principles of anti-aliasing and how are they used? What is acoustic transmission loss? What is decibel addition and how is it used to assess and reduce noise? How are acoustic directivity patterns used for noise source location, beamforming, holography and sound power mapping? What is a temperature coefficient and how is it applied? What is TEDS?