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)
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.
Answers
Hi and thank you for posing your question to the community. I've shared your post with the CTS Holders Room so that they can engage directly with you on the topic. You can follow it here: https://xchange.avixa.org/rooms/cts-holders-group/conversations/60388
