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OffTopic > Recording - CD Quality

#104953 - sgeos - Wed Oct 04, 2006 5:13 pm

What is the cheapest way to record acceptable CD quality voice samples. I will be recording 98 ten second samples. For a CD- imagine that. (blue book, if anyone cares)

acceptable != hearing my computer's hard drive when the volume is turned up. =)

-Brendan

#104992 - keldon - Wed Oct 04, 2006 10:37 pm

The cheapest way is to use your headphones as a microphone and the 'lousy' pre-amps in your sound card to boost the volume.

Next is to buy a cheap dynamic mic for a dollar. That can get quite good results for vocals.

You will hear your computer hard-drive if you have amplified the signal picked up by the microphone enough to hear it.

#104994 - gauauu - Wed Oct 04, 2006 10:50 pm

I've found that the cheap computer mics (like the ones for skype and whatnot) work well also. Get as much distance between you and the computer (or other noise generators) as possible, and angle the mic away from them (although that doesn't help so much if it is a condensor style mic).

Keep the mic recording volume relatively low, and get right up next to the mic when you speak. Record about 10-20 seconds of "silence" which will be useful for getting a background noise profile for noise removal if you end up being able to hear computer fan or other background in your recording.

When finished, depending on the audio quality, you may want to use something like audacity to amplify the recording to the maximum non-clipping volume, and then use the noise removal, profiled with your silence that you recorded, to remove any background hiss if it's noticable.

#104996 - keldon - Wed Oct 04, 2006 11:20 pm

gauauu wrote:
although that doesn't help so much if it is a condensor style mic

Condenser mics can be directional, non directional, omni-directional or bi-directional just like dynamic mics. They are condenser mics because they capture the sound using capacitors, requiring phantom power.

The signal to noise ratio will goven the amount of noise in your recording. Your mic provides [something like] a 1/10th of the voltage that a CD player would provide meaning that it must be amplified before the DAC process. This is carried out by a preamp, but the crappy ones in most sound cards produce a lot of noise when doing so.

So even if you record at a low volume, you will still be hearing a lot of noise either way. Recording silence should help programs like audacity profile the noise - I would guess that it uses the spectral analysis method of counteracting noise; although it may not.

#105102 - tepples - Thu Oct 05, 2006 11:27 pm

keldon wrote:
Recording silence should help programs like audacity profile the noise - I would guess that it uses the spectral analysis method of counteracting noise; although it may not.

As far as I know, it does. I seem to remember giving a broad description of Cool Edit's algorithm to an Audacity developer who wanted to know how a noise killer worked.
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#105144 - sgeos - Fri Oct 06, 2006 11:50 am

tepples wrote:
As far as I know, it does. I seem to remember giving a broad description of Cool Edit's algorithm to an Audacity developer who wanted to know how a noise killer worked.

Do you happen to know of any command line noise killer filters? (wav format).

My friend recommends a $20 to $40 (Canadian) microphone:
Quote:
As for the microphone, what you really need is the muffler. that poofy part on the head of the mic. The poofier the more background noise is muffled. Yet it would pick up your voice very well.

My mic has some stats listed (headings not listed because I don't feel like translating them):
Noise canceller microphone
300Hz~8KHz
~10kΩ
.-61dB?4dB

Do these mean anything useful?

-Brendan

#105162 - wintermute - Fri Oct 06, 2006 2:46 pm

One of the best means of recording I've ever found was a cheap radio microphone I purchased from the local market for the princely sum of ?5 (approximately $10 ). This allows getting a lot of distance between the audio source and the computer - I can actually record from the street outside :)
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#105169 - keldon - Fri Oct 06, 2006 3:21 pm

Most of your noise is created by the preamp in the sound card, so no matter what unpowered mic you have you will be getting noise produced by it. Without a preamp there is no good mic. If anything try to borrow one, you might be lucky to know someone with a device that has a decent preamp.

Mixers have preamps, and the better the mixer the better the preamp. Some effects units will have some sort of preamp, I know the korg multi effects unit does, so you might be able to find some guitar playing friend with all the kit you need.

You can also try the 20dB+ on a DI box or an echo chamber; just anything that can allow you to bypass you stock card's preamp.

Quote:
Do you happen to know of any command line noise killer filters? (wav format).

There are plenty of noise reduction algorithms/techniques, but they are all destructive and lose quality to some degree. I did google and couldn't find much on command line programs. I'm sure it's there, I've just got a dirty cold and I was a little sloppy with my search.

#105266 - sgeos - Sat Oct 07, 2006 3:15 am

pts' Linux audio recording tutorial seems to list command line tools- for linux, at least.

-Brendan