This question is from CTS-D AVIXA Activity which is from Design 1: ENV - Microphone. Microphone Pre-Amp Gain Required You need to choose a microphone for a new auditorium. Your sound source is a presenter located 2 feet (609.6 mm) away from the microphone, with a measured SPL of 72 dB. In order to route and process that signal, you need to amplify the microphone level signal to line (0 dBu)

Anand Munuswamy Sachudanand on Jul 17, 2023 • 1 answer
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Most microphone preamplifiers will provide around 60 dB of amplification. You have a choice between two microphones: SM58: A Dynamic Microphone Equivalent Voltage Specification: -54.5 dBV/Pa (1.85 mV) MX418 A Condenser Microphone Equivalent Voltage Specification: -35.0 dBV/Pa (17.8 mV) 1 Pa = 94 dB SPL Answers: Pre-Amp Gain Required SM58: -74.29 dBu MX418/C: -54.79 dBu Till this it's OK and have understood. But given on same page is: Assuming you have a 60 dB gain in your microphone pre-amp, the SM58 is not sensitive enough for this application. The closer you can get to 0 dBu, the better the microphone will be for the application. You need 83.5 dB, but you only have 74.29 dB gain, leaving you 9.21 dB short. I have doubt on how this 83.5 dB has come. Could someone help me, please.


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Lisa Matthews, CTS - AVIXA on Jul 17, 2023
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