A background rumble appears in a sound from microphone in Sound blaster Live.

Hello!
A background (about 50hz) rumble appears in a sound from microphone.
Windows XP SP2.
I tried two headsets (which surely are good). The rumble decreases if
I touch the computer case. I checked the inside of the case, did not
find any improper contacts. The sound card is Creative sound blaster
live ct4830. I tried the latest Microsoft and Creative drivers. The
Creative driver does not output sound from microphone to speakers at
the same time, but only from a recording from the microphone. How to
prevent the rumble?
Best regards,
Dima

 

"D" wrote ...

In common use, "rumble" applies to low frequency *random noise*
such as from an air duct or a subway train or from a distant highway.

If you are hearing interference from your power mains (presumably
50Hz if you are posting from Russia), that is called "hum" and it is a
very *constant* tone.

We will assume that you mean that you are hearing interference
from power-line hum. If it is *rumble*, then it is acoustic and you
should be able to hear it with your ears, no headset, no computer.

Does it hum when no headset is plugged in?
If so, then there is a problem with the computer or sound card.
If no, then *both* of your headsets have a problem

Does the hum change when you move the headset around
the room?

Does it hum when you try using a differen computer mic?

rcrowley posting from rec.audio.pro

 

Is "rumble" a precise term or are we chasing a mains hum?

 

IMO, this undoubtedly means you have a ground problem. As if
"about 50 Hz" was not enough of a tipoff. It's always 50 or 60.

But it MAY just be a totally crappy microphone. Try another one,
preferably a good one.

If it's NOT the microphone, I am not a technician so I can't
tell you how to fix it, but first thing you should do is check
that everything to do with you system is plugged into the SAME
AC circuit, preferably same outlet with power bar(s), and then
you can buy or borrow (or steal I suppose) a little gizmo which
you plug into the wall outlet and it tells you if everything's
OK. Other than that, ask a technician.

That si impossible. Check your mixer volumes, mutes etc.
Watch out for feedback, it can be VERY unpleasant, but no sound
card manufacturer will disable mic to speakers direct just
because of that.

 

What are you recording, I know you state form a microphone, but are
you plugging in something else into the microphone socket? If so that
would be the problem try plugging it into the line in socket.

If it is a microphone then make sure that it is being fully pushed
home, if it is then try another one (they aren't exactly expesinve).

Others have mentioned ground loops etc, but try the easy bit (normally
the cheapest bits) first.

As a matter of fact I get a continual low level 50hz hum from my line
in post unless I actually plug something into it then it dissapears,
so you could also try turning off all ports you are not using before
doing your recording.

 

Thanks Richard Crowley for your explanations!
It does not hum when no headset is plugged in.
One of the headsets is brand new and checked.
Yes, the hum changes when I move the headset around the room: the
further from the computer case the louder.
Yes, it hums when I try using a differen computer mic: both headsets.

 

Yes, we are chasing a mains hum.

 

Thanks thanatoid for your suggestions!
I checked my mixer volumes, mutes etc. and did not find anything
wrong. I uninstalled the Creative driver.

 

Thanks kráftéé for your suggestions!
I checked with brand new headset - the same.

 

"D" wrote ...

Then you can eliminate any problem with the computer,
the sound card, or any software including drivers, etc.

What does "checked" mean? Do either of the headsets work
OK on another computer?

I would take a wild guess that it has a shielding or grounding problem.

The problem may be with the basic design if both headsets
show the same symptoms.

 

Sounds like it's not the mic, but you may have a short of some
kind or ground loop in your headphone connection. If the
headphone connection is at the front of your machine, a
technician has to check it.

If it's a jack on the soundcard, you can remove the sound card
and take it to a technician without having to take the whole
computer over there.

 

Theanks Richard Crowley for your suggestions!
The hum is from speakers, not from the case. Yes, either of the
headsets work OK on another computer.

 

Thanks thanatoid for your suggestions!

 

Thanks Richard Crowley for your suggestions!
The hum is from speakers, not from the case.
Yes, either of the headsets work OK on another computer.

 

The problem is likely caused by the combination of "speakers" being
disconnected by the insertion of the head phones AND the volume knob of
the speakers being cranked up rather high. Now the speakers are
amplifying the hum of the little power wart.

 

Thanks Richard Crowley for your suggestions!
The hum is from speakers, not from the case.
Yes, either of the headsets work OK on another computer.

 

Then it is possible that the sound card has a problem.
Since the sound card feeds power into the microphone in
the handset, the filter capacitor on the microphone power
may have a problem that is letting 50Hz hum get injected
into whatever microphone is connected. You would not
hear this unless a microphone was connected. Since the
headsets work OK on another computer, that casts the
suspicion back on the sound card.

 

Perhaps the sound card just has the problem that it's a Soundblaster
Live! and you're using the mic input. A SB's Line in/out is
acceptable quality but the mic input is a joke.

 

You're welcome and good luck. Check if a new sound card isn't
cheaper than fixing yours!
Creative is basically OK and ultra-compatible although
perfectionists complain about the sound/specs.
M-Audio if you're a musician or have very good ears.
Turtle Beach is pretty good too if you can find one.

 

Thanks Bob I for your explanation!
How can the speakers amplify the hum of the little power wart if they
are disconnected by the insertion of the head phones?
A Sony ECM-T6 microphone and another desk-top microphone don't hum! A
new Koss sb/45 headset and Philips SBC HM300 headset hum from their
microphones.
How to make Koss sb/45 headset microphone work?
Best regards,
Dima