【 Weak current College 】 microphone sensitivity calculations

Sensitivity is the microphone on the unit of sound pressure excitation output voltage and input sound pressure ratio, it is in mV/Pa. As with circuit-level metrics consistent sensitivity can also be a decibel value.

Early DB more units dBm and dBV says:

0dBm = 1mW/Pa, that is, under the input sound pressure 1Pa to 600 Ω load of 1mW power output defined as 0dB;

0dBV = 1 V/μ b a r, in 1 μ b a r input sound pressure produced by 1V voltage output defined as 0dB.

Now the unit of DB d B μ says:

0 d B μ = 0.775V/Pa, coming under the input sound pressure 1Pa Mike 0.775V voltage output defined as 0dB (so that the microphone sound pressure-voltage level measurement after the conversion, the circuit generally 0 d B μ = 0.775V this reference units).

Obviously, no matter how sensitivity that we can convert it to d B μ, subject line enter into Pa this unit (own note: here add: 1Pa = 10 μ b a r. Back in the calculation of the useful to the formula) for example: NEUMANNU89 microphone sensitivity is 8mV/Pa, can directly by 20lg [(0.008V/Pa) ÷ (0.775V/Pa)] its sensitivity is about-40 d B μ.

Another example: AKGC414 microphone sensitivity to-60dBV by 0dBV = 1 V/μ b a r = 10V/Pa (here used the formula mentioned before: 1Pa = 10 μ b a r) to find the sound pressure-1Pa 60dBV output voltage X:20lg [(XV/Pa) ÷ (10V/Pa)] =-60

Conclude that X = 0.01 (V), that is, its sensitivity to 10mV/Pa. Then-20lg [(0.01V/Pa) ÷ (0.775V/Pa)] can have its sensitivity is about-37 d B μ.

MIC related terms

2:1RuleofAmbience

2: 1 environmental sound capture rules. Means that if you want to capture the same amount of indoor environment of sound, heart-shaped microphone distance to the sound source should be the whole point to the receiver to the audio source distance of 2 times. This is ideal for indoor environmental sound recording is very important.

3:1RuleofMicrophonePlacement

3: 1 microphone placed rules. Refers to the simultaneous use of two microphones on the same sources during recording, the second microphone to 1 microphone distance, is the first handset to the sound source distance of 3 times, the best results. For example, suppose the first handset to the sources of the distance is 1 ft, 2nd best place point the microphone should be at the first microphone position 3 feet, because it can be a time delay between thanks to the microphone and the differences in the problems caused by phase-reduce to a minimum. In addition, the rules for using multiple microphones against multiple sources for the recording of it still applies. Specifically, suppose we now want to use two microphones on 2 different audio sources for simultaneous recording, so that the two microphones, the distance between them should be at least to the respective sound source distance of more than 3 times. Finally need to remind you that any rules are experience, is for informational purposes only. In actual operation, you also need a concrete analysis of specific issues. Don't forget, your auditory reaction is the world's best rules!

A-BStereo

A-B stereo. Sometimes called "time delay stereo". Refers to the simultaneous use of two intermediate with a certain distance intervals of all point to the receiver, to the same stereo sound and image capture microphone recording techniques. Because of the way in this recording, microphone distance will give audio signal brings the time delay and phase differences, and the ear of the auditory system is based on these different levels of sound signals to the sources, spatial positioning and eventually formed in the brain that signal sound field of stereo sound and image, thereby giving the listener very strong sense of stereo space and, therefore, in the microphone further away from the sound source, the "Omni microphones + A-B stereo recording" combinations, usually recording masters preferred solution. As with all the reasons to the microphone, mainly because it in no matter how far away from sources of cases, the precise factual captured audio sources of low-frequency section. By contrast, the directivity microphone not vulnerable to the effects of proximity, but also easy to more distant from the sources of loss of low-frequency response.

AbsolutePhase

Absolute phase. Typically, in the vast majority of the microphone, the diaphragm is positive pressure (positivepressure) is generated in the anode voltage when output. In other words, if the signal polarity in the transmission path not changed, you should build in speaker Terminal anode voltage and then through the speakers at the listening position into positive pressure wave (positivepressurewave). The sources of original polarity can be in phase with speakers to reproduce the phenomenon that is the so-called "absolute phase".