Did YOU KNOW?
When developing a speaker, testing performed on that speaker, such as rub and buzz, is required to determine the noise or hiss and other imperfections of the product under test, especially at low volumes. Being armed with this information for new product design, the research and development engineers can use this data to improve the product and minimize the unwanted noise for better clarity and enhanced sound quality.
Without the proper tools (or sensors) to test the speaker, the engineer can’t be sure if the noise or imperfections to the sound wave is coming from the product they are developing or the very sensor they are using to test the product. This is why more audio engineers are turning to lab grade test and measurement microphones to aide in developing their products. When used in the proper environment, such as a noise free room (anechoic chamber), these IEC compliant sensors have the capability of measuring down to 5.5 dBA (typical) with a 0V (prepolarized) or 200V (externally polarized) test and measurement system. All of the components in the measurement chain: microphone, preamplifier, cables, signal, power supplies, data acquisition systems (DAQ), computers, and test area, can contribute to the noise that the complete system is capable of measuring.
Why Is The PCB Model Better?
Below is a comparison of a typical audio microphone vs the PCB model 378A33 lab grade test and measurement system. Audio microphones typically have a 5 to 20 dB higher noise floor. It is important to note that that just a 3 dB increase is a doubling of sound pressure level (SPL.) Thus, audio microphones have a significantly (several times) worse low noise measuring capability than that of a laboratory grade microphone, in pounds per square inch (psi).
PCB models 376A31, 376A32 and 376A33, are all 48V phantom powered microphone and preamplifier systems. These systems allow any IEC 61094-4 working class standard microphone to be swapped on the 426A14 preamplifier to tailor the microphone (sensing element) to the specific requirement for the application. The 376A32 has a 15.5 dBA to 137 dB dynamic range and 3.15 Hz to 20 kHz (+/- 2 dB) specification, making it great for low noise measurements, such as; disc drives, fans, and component testing. Model 376A33, which is the most common product for the audio market, has a great blend of low noise floor measurements and relatively high frequency and amplitude capability, ranging from 22 dBA to 150 dB and 3.15 Hz to 40 kHz (+/- 3 dB). The 376A33 is perfectly suited for a wide range of applications including speaker and instrument testing, instrument and speaker modeling, and high quality live or studio recording. The 376A31 has a dynamic range of 40 dBA to 165 dB and a frequency capability of measuring 4 Hz to 100 kHz (+/- 3 dB). This is recommended for high amplitude and high frequency measurements, such as; high quality recordings of bomb blasts, gun shots, or loud peak impulse responses of a kick or snare drum.
Depending upon the capability of your test room and ancillary test components in the signal chain, either the 376A32 or 376A33 can be selected for your low noise speaker and component measurement tests.These will help you determine that the noise you are testing is from the object under test and not the microphone sensor used to test it.
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