Problem with Mic Frequency Response

[tirolator]

Hello

Should I not have a flat response with the Mic? I made no measurment - just press red Button in the RTA.
I am concerend about the rising curve at about 8k...
thx

 

[sam_adams]

Should I not have a flat response with the Mic?

No you wouldn't see a perfectly flat line with the mic because it is, of course, measuring the background noise of the room. Even in a very quiet space with the mic capsule isolated from the environment, there will still be the self-noise of the microphone to deal with.

 

[tirolator]

Thx for reply. Yes I know that it would not be complete flat, but I thought at the Topend it should be more flat when it is very quiet. How should I make a correct measure then? At deeper frequency it’s not sutch a problem. But why does it rise so mutch at the top end?

 

[sam_adams]

Thx for reply. Yes I know that it would not be complete flat, but I thought at the Topend it should be more flat when it is very quiet. How should I make a correct measure then? At deeper frequency it’s not sutch a problem. But why does it rise so mutch at the top end?

All mics will have a degree of self-noise. Some of it will be caused by the mic electronics or the preamp and some of it—at the very lowest level—is caused by air molecules bouncing off the mic diaphragm. USB mics have that rising curve because of the noise shaping in the ADC in the mic. Does it affect your measurements? Given that the noise is at such a low level when compared to a speaker signal at 75 dB to 85 dB, probably not.

 

[tirolator]

All mics will have a degree of self-noise. Some of it will be caused by the mic electronics or the preamp and some of it—at the very lowest level—is caused by air molecules bouncing off the mic diaphragm. USB mics have that rising curve because of the noise shaping in the ADC in the mic. Does it affect your measurements? Given that the noise is at such a low level when compared to a speaker signal at 75 dB to 85 dB, probably not.

Thx for your reply - no I think it should affect the measurment, but how do I know if my mic measures correct? How do I know if it not adds somethin what I dont want.
Just for example - I use REW in Cars to tune the Systems. Does not a crazy curve from a mic get added to my acoustic measurement from the Speakers? For Example - the mic shows at 8khz a peak from 3db and this 3db get added on top of my acousticcurve. Or do I missunderstand something?