Phantom low frequency noise at ambient

[rickter]

Hi all. What does your ambient response look like?
I tried inside house, basement, calibrated, followed all config steps in windows, different computers, outside of house, at work, you name it.

Low frequency response at ambient is artificially high down to 5Htz. It can't be room modes beause I get a similar resonse out doors minus the singing birds.

I compared it to a ECM8000 analog using True Audio RTA. The ECM8000 seems more realistic with low frequencies reasonably similar to high frequencies in a quiet room.

This mic seems to be picking up or creating low frequencies.

I contacted tech support and they suggested I try the forum. :(

Any ideas before I send it back?

[Mechanic]

Re: Phantom low frequency noise at ambient

Are you playing the recommended test track(s) at this time ?

[rickter]

Re: Phantom low frequency noise at ambient

Quiet room. No signal.

[DrBoar]

Re: Phantom low frequency noise at ambient

I noticed that you have sine sweep and smooting on. Could it be an algoritm artefact?
Try set it to pseudo noise and no smoothing?
Have you tried a laptop not connected to power? It is a long shot but those two peaks at 120 and 180 could be mains harmonics, if you live were there is 60 Hz mains.

[Face]

Re: Phantom low frequency noise at ambient

I experience this in one room in my house, I have no idea why it happens there but nowhere else.

[rickter]

Re: Phantom low frequency noise at ambient

I'm gussing you case is room modes. My phantom low frequencies happen everywhere, even in the woods on battery. Harmonics is a good idea but 60 Htz response is lower, 20Htz is very high. 5Htz is even higher but I cut that off in my pic. I'll change the noise setting and smoothing but I don't expect that to help.

Thank all of you for your comments.

[DrBoar]

Re: Phantom low frequency noise at ambient

If you save curves from different locations and add them to the same graph how well do they match?
20 Hz at 70 dB is at the edge of audiability but 50 dB at 400 Hz is way above such thresholds, does it sound quite?

I can hear the mechanical ventilation in my house but if I turn that off it is really really quite. Perhaps I will take a measurement...

[rickter]

Re: Phantom low frequency noise at ambient

The curves from different locations generally match. I've measured everywhere it's quiet. I live in the woods and have taken the MIC outside, same results. I also compared the curve to a ECM8000.
The 8000 has a realistic, relatively flat curve at the noise floor. Can others post their noise floor curves with the OmniMic?