Audio recording background noise

For a long time time I've been trying to get rid of the background noise that appears in every audio recording I make with my computer. Tried different microphones, different sound setting, drivers.

Interesting fact - the volume of this sound is equal whether I use and internal notebook microphone or an external one. I tried really good mics, so I'm sure the problem is not in it.

Laptop on which this problem appears in HP Probook 4720. OS - Windows 7.

P.S. Read an answer to a similar question: Annoying sound from microphone in headphone. Tried everything that was mentioned there. Only I don't have a "DC Offset Cancellation option". And when I disable "Noise Suppression" and "Acoustic Echo Cancellation", noise only becomes more noticeable.

What should I do?

EDIT: Example of the background noise I'm describing: http://eos-soft.com/files/noise.wma.

I think you have 2 options:

1. following on from @slhck's suggestion you should consider an external, say USB-based, audio recording device, however you should also consider noise caused by ground-loop/earth loop. Here's a test for you: unplug your laptop from the mains, do you get as much noise or is it reduced when unplugged? If reduced noise when unplugged, then ground-loop is contributing to the noise. This is fairly common and not a fault as such (nature of the equipment really) and can be remedied by ground-loop isolation such as a ground-lift box or DI-injection box, common low cost pieces of kit from people like Behringer.

2. Don't use the laptop at all for recording, instead use a standalone digital flash-memory based recorder (this is the better option of the 2), one that can accept an external mic if required, such as the Panasonic RR-XS410 for around 50$ / 50 pounds on ebay. Also Olympus models. A 3.5inch jack to XLR mic adapter is available from audiospares.com The recordings can be transfered into the laptop, for editing, by USB, and with Panasonic via the microSD card as well. These recorders record high bitrate mp3 and the panasonic also records wav.

Finally have a look at audio discussions on soundonsound.com and also the audio recording stackexchange site.

Interesting fact - the volume of this sound is equal whether I use and internal notebook microphone or an external one

This, in conjunction with the fact that you're using a laptop only leads to one possible solution. You need to buy an external sound card or an audio interface. The problem is that built-in sound cards need to amplify the signal that comes in from the microphone. When they amplify the signal, they also amplify the noise that is sent with the microphone. There will always be a certain noise level.

However, since the sound card is on the mainboard and close to other devices such as a CD/DVD drive, a Wi-Fi antenna, spinning fans, these will generate interferences as well, which will then be amplified by the sound card.

This is why changing the microphone does not make a difference. Its signal will have to pass through the sound card.

"Background noise" is very generic, but unless you can post an example that shows a different kind of noise, I'd say this is the problem. I've experienced it on many laptops that are improperly shielded.

I record and post a lot of speech in an amateur setting and on one system there is always the exact same signal. The guys who record it tried everything made it much better but never totally gone, finally I just decided to make taking it out part of the post recording process. No doubt any software has the same tools, but I use Audacity and have found the noise removal tool to be invaluable. I just select a second of silence to get the signal profile, then select the whole track and repeat the filter. 3 clicks and a few seconds later I have a clean track. PS if you are doing speech and haven't seen Levelator it is magic. Of course if you are working on producing music neither of these will probably be what you need.

I had a terrible, constant hum, and I followed therobyouknow"s advice copied below:

however you should also consider noise caused by ground-loop/earth loop. Here's a test for you: unplug your laptop from the mains, do you get as much noise or is it reduced when unplugged? If reduced noise when unplugged, then ground-loop is contributing to the noise.

I am using a usb mic to record voice audio in garage band. I unplugged my computer and went to battery power. This totally eliminated the hum. Thanks!!!

As suggested by others, it is advisable to record using an external sound card. A USB sound card will solve the problem. This one is purely noiseless and capable to handle XLR or phono mics. Second part is to avoid surroundings noise; switch off fans, AC and you should have sound proof rooms. Even while recording in professional studios we face noise problems. For that you can use noise remover plugins and finally the kind of software you use for recording.