Microphone Hum

[Flossi]

I am using VS11+ and a Optimus Unidirectional Condenser Mike Type 33-3017 --600 ohm Impedance. When narrating a project a hum is heard in the background , does the fault lie in the VS or the computer , I have a Dell Inspiron 530 Viv E 4400 Core Duo 200Ghz 800Mhz FSB 2 Mb cache Dual Ch. 2 GbRAM 250Gb H.Drive 572 Mb nVidia Ge Force 8300GS ( 1 Gb memory ) Video Card. Vista Home Premium Rev.1.03

[sjj1805]

Without seeing your exact set up we can only guess.
If you have a computer desk and the microphone is placed on the desktop then it is possible that it is picking up the sound of your CPU rather like when Tonto tells the Lone Ranger that there is a train approaching by placing his head on the railway track.

[MrA]

I am using VS11+ and a Optimus Unidirectional Condenser Mike Type 33-3017 --600 ohm Impedance. When narrating a project a hum is heard in the background , does the fault lie in the VS or the computer , I have a Dell Inspiron 530 Viv E 4400 Core Duo 200Ghz 800Mhz FSB 2 Mb cache Dual Ch. 2 GbRAM 250Gb H.Drive 572 Mb nVidia Ge Force 8300GS ( 1 Gb memory ) Video Card. Vista Home Premium Rev.1.03

Hum is created by having a microphone on and a recording device "hearing" the same microphone.

Grahically, picture taking a picture looking into a mirror with a mirror as the background. You see a lot of "mirror" images. In audio, this is called "hum".

Just move the mic..

[etech6355]

Hum is created by having a microphone on and a recording device "hearing" the same microphone.

I think maybe you mean Feedback. Hum can also feedback when the mic is to close to the speakers..

Hum is usually power line interference, 60hz or 120hz, commonly caused by poor shielding, ground loops, capacitive coupled .or an open ground.
Low cost mics and low cost wiring.

This is why low impedance balanced mics & inputs are better (XLR mic's & cables).

Because he's using a capacitive mic (which puts out more voltage), maybe he could try the Line-In connector, worth a try.
The computers unbalanced mic input is usually pretty noisy.

[2Dogs]

@Flossi

and if you get the same hum when you try making an audio recording with, say, Windows Sound Recorder, using the same mic, it should rule out VS as the cause.

[etech6355]

Yes, and if he stays with the same mic the only chance he has is to do what "MrA" suggested which is move the mic away from the source of interference, which could also be his hand if he's holding the mic.
I wonder if his computer & monitors plus connected equipment are properly grounded.

[DVDDoug]

Optimus Unidirectional Condenser Mike Type 33-3017

That microphone has balanced low-impedance* output. Your computer has a high-impedance unbalanced input. Are you using an impedance-matching transformer? If you are using a simple adapter (without a transformer) your signal will be too low. When you increase the gain to compensate, you will also increasing the background noise. And, the unbalanced connection will be more prone to picking-up hum/noise.

Keep in mind that the signal-to-noise ratio is affected by both the signal and the noise. (A strong signal can overcome the noise, and a weak signal can get lost in the noise.) So, speak with a strong-clear voice and get as close to the mic as you can without picking-up breath noises, or exaggerating the proximity effect (bass boost), etc. Of course, you may have to reduce the gain to prevent clipping (distortion).

I can think of 4 possible sources for the noise:

1. Electromagnetic hum from the AC power all around you. (This is the most common source of AC "hum".) You can minimize this by using shielded-balanced cables.

2. AC power hum (or other electrical noise) getting into your soundcard. If you are using an external preamp or mixer, these can have the same problem. In this case, the only solution is a stronger signal, or better equipment.

3. Mechanical vibration. Put the microphone stand on something solid.

4. Acoustic noise. Find a quiet room and turn-off the heater and/or air conditioning.


If you can keep the hum/noise low enough, a noise reduction filter may be able to eliminate it completely. I think Video Studio has an audio noise reduction filter, but I use a separate audio editor.



*This is good! Professionals use balanced, low impedance microphones because they have good (electrical) noise immunity.

[dazzler2]

Of course preventing hum is a separate issue from getting rid of it once you have it.

I had hum....from my camcoder on irreplaceble video clips, caused by the speaker being too far from the camcorder mikes. Lacking an external mike, I now use a small Olympus digital recorder. It is amazing what you can do with it.

Two excellent programs for deleting hum or inserting moments of silence etc. to block instantaneous noise are Goldwave and Audacity.

I've had excellent results with Goldwave and less so with the much raved about Audacity.

With Goldwave you can load an avi which will allow you to work on the sound only, leaving the video untouched. You then save the cleaned up sound as a wav file. I then place the cleaned up wav file in an audio track directly under the video avi file it's associated with in my project. Then I mute the audio in the avi and play the rest together after selecting project.

Audacity was unrelable, mostly crashing when I tried to load a separated wav file for cleaning.

Hope this helps.
Don

[etech6355]

HUMMMmmmmmmmmmmmmmmmmmm

30hz, 60hz, 120hz Notch Filters (for 60hz power, USA etc)

[Flossi]

First let me say thank you for the many responces posted.I have not got a matching transformer. I've tried Picture Gallery --no difference .
The hum is more of a shsss than a buzz .There is a small phut sound as the mic is switched on / off. I did'nt have the problem a month ago. Recently each time I log on I get a 'Speech Recognition' box which I cancel, is this a mere coincdence ? Thanks Flossi