Audacity Forum

PGA wrote:I have, this afternoon, performed the same investigation into the recording of "Silence" on my Acer laptop, It is far noisier than my desktop system (-36dB as against -80dB

It's very common for the recording input of laptop to be very poor due to the analogue (pre-amp) inputs.
If your sound card settings have a "Mic Boost" setting, then turning that off is likely to produce a big drop in the noise floor level (though recording from the microphone is then likely to be far too quiet).

PGA wrote:I'm beginning to think that I might, unintentionally, have hi-jacked this topic.

I think the original topic has now been answered.
I probably extended it further than necessary due to my lack of understanding about how modern Windows sound systems work, but I'm now satisfied that the noise level reported by audio_guy_77 is nothing more than the normal noise floor of the sound card.

OK. I'm happy to leave this subject unless anybody else chimes in.

Ok here is my result on yet a 3rd mother board running a fresh install of Ubuntu 11.10.

I am using a good quality E/V mic with a good external pre-amp and feeding that into line in since most mic channels on PC sound cards and on board sound are very bad.

I did a test recording to be sure Audacity was recording my voice.

Though I am just clicking on the input level meter to check for noise, I did make sure preferences were set to 32 bit float and no dither.

If I completely close the Audacity input volume slider I get no noise when I click on the input level meter. YEA!

However, cracking open the Audacity input slider just a hair, with no cables or anything attached to the on board sound, the noise immediately jumps up to -30, -36 per channel. Open the Audacity input slider all the way and the noise is -9 to -12 per channel.

So Linux isn't the cure all. At real world setting I get lower residual noise levels on Windows.

I can buy a Zoom, Roland or similar recorder and then move the files over to Audacity to edit but that is an added expense and hassle.

Ideas? Thanks.

audio_guy_77 wrote:If I completely close the Audacity input volume slider I get no noise when I click on the input level meter. YEA!

However, cracking open the Audacity input slider just a hair, with no cables or anything attached to the on board sound, the noise immediately jumps up to -30, -36 per channel. Open the Audacity input slider all the way and the noise is -9 to -12 per channel...
...I can buy a Zoom, Roland or similar recorder and then move the files over to Audacity to edit but that is an added expense and hassle.

Ideas? Thanks.

Add a YEA! from me, too! On my Win 7 desktop PC, if I close the input device slider in the Mixer Tool bar, I also get a true flat line. And if I crack it open (to 0.1) I get some residual noise.

As for ideas... buy the Zoom, Roland, Tascam, Edirol or whatever and enjoy making location recordings, too! (OK, that's maybe not your scene and I can understand that)

regards,
Peter

Since you threw in an aside question not yet answered, I'll do so...

PGA wrote:There are some, infrequent, occasions when I would like to capture sounds (from the Internet) that are already playing on my PC. Those sounds are already digitized - aren't they? - and so "recording" should just be a case of capturing that digital data - shouldn't it?

Not with "stereo mix" - that captures the audio playing on the sound card (hence already converted to analogue) and then converts it back to digital.

To capture computer playback digitally you have to grab the sound "virtually" before it gets to the sound card output. I can't think of any reliable program that does this for free on Windows, but paid programs that do it include Virtual Audio Cable and Total Recorder.

On Macs, you have to use programs that grab playback digitally, because Apple does not permit capturing audio as it plays.


Gale

PGA wrote: On my Win 7 desktop PC, if I close the input device slider in the Mixer Tool bar, I also get a true flat line. And if I crack it open (to 0.1) I get some residual noise.

Is the true flat line impossible to amplify - open "Amplify" and "New Peak Amplitude" is "-Infinity"? I can't get that without muting the input in Windows.


Gale

Hi Gale,

Firstly, thanks for the answers to the "aside" questions. On the other point, Amplify does not show "-Infinity". The frequency spectrum graph and the Amplify screen are attached below.
I see no sound in the plot: I hear no sound from the speakers (probably a limitation of hardware or humanware); yet Amplify is willing to amplify some sound. If I am interpreting the Amplify details correctly, the effect is going to lift the sound by +50dB, taking the peak sound level to -30.8dB. So the loudest sound in the original recording sample is at -80.8dB, right? So where is that sample in the frequency plot? If it's peak is at -80.8dB there should be colour for it all the way down to -96dB (and beyond), shouldn't there?

PGA wrote:the effect is going to lift the sound by +50dB, taking the peak sound level to -30.8dB. So the loudest sound in the original recording sample is at -80.8dB, right?

Correct. The "peak" level (before amplifying) is -80.8 dB.

PGA wrote: If it's peak is at -80.8dB there should be colour for it all the way down to -96dB (and beyond), shouldn't there?

Not quite. The Spectrum plot is calibrated so that a 0 dB sine wave will show as (approximately) 0 dB.
Because "noise" is made up of very many frequencies, each FFT frequency band will be substantially below the overall peak level.

If you go into "Preferences > Interface > Meter / Waveform dB view" you can change the spectrum scale to allow Plot Spectrum to go below 96 dB.Try setting it to -145.

OK, At -145dB I see masses of noise across all frequencies but at a very low level (below -100dB).
If I have properly understood everything I have been taught over these last few days, this is noise from the soundcard (or noise from elsewhere in the system that has been picked up by the soundcard). At -100dB and below, it is going to be almost, if not entirely, inaudible to most folks at normal playback levels; and totally swamped by any "real" signals from such as music, voice or natural sounds. So I have nothing to worry about. Not that I was worried; I was merely curious.

PGA wrote:If I have properly understood everything I have been taught over these last few days, this is noise from the soundcard (or noise from elsewhere in the system that has been picked up by the soundcard). At -100dB and below, it is going to be almost, if not entirely, inaudible to most folks at normal playback levels; and totally swamped by any "real" signals from such as music, voice or natural sounds. So I have nothing to worry about. Not that I was worried; I was merely curious.

Yes I believe that is the case.