Audacity Forum

mike656 wrote:-5db down? When recording i'm reaching -6db on audacity (if i'm reading it right).

0 dB = Red Line. Maximum signal level.
-6 dB = Half of full scale amplitude. Equivalent to a signal that goes between +0.5 and -0.5 on the vertical scale in Audacity.
-12dB = Quarter of full scale. Equivalent to a signal that goes between +0.25 and -0.25 on the vertical scale in Audacity.
-24dB = 1/8th of full scale. Equivalent to a signal that goes between +0.125 and -0.125 on the vertical scale in Audacity.
-96dB = very very quiet. The smallest unit of amplitude in 16 bit digital audio.
- infinity = silence.

Notice that the figures are given as negative numbers. That is because "dB" is a ratio rather than an absolute measurement - it is always referenced to a given quantity. In the case of audio signals, the "dB" figure is usually with reference to the maximum signal before clipping (0dB). In the case of digital audio, that is a signal that goes from +1.0 to -1.0 (full scale on the vertical scale on Audacity tracks).

As we are counting down the dB from 0dB (maximum) to "minus infinity" (silence), -5dB is just a little louder than -6dB. (strictly speaking it is slightly greater amplitude, but because of the way our ears work it is also dependent on the frequency whether it is louder or not. -6dB at 1kHz sounds very much louder than -6dB at 100Hz, or -6dB at 10kHz).

I think that I measured the maximum peak level in that clip at -5.2dB, so yes you will have been seeing a peak level on the recording meter of around -6dB. You can see the dB level on the recording meter with more precision if you grab the meter with your mouse and drag it around and stretch it to the full width of your computer screen (you can then drag it back into a "docking" position and it will remain the size that you have made it. Also, in Audacity 1.3 you can switch to a "linear view" which is good for viewing the peak levels more accurately.

mike656 wrote:Yeah i'm recording off of streaming radio broadcasts.

When they made the radio broadcast they limited the peak levels so that all of the highest peaks are at about the same level (dynamic compression). Because there are no sudden spikes to catch you out you could set the recording level a little higher, say around -2 or -3 dB. You would not try that with a live microphone recording as you would probably find occasional peaks that jump up 12dB higher than anything else, and if you have not allowed sufficient "head room" then those peaks will clip.

mike656 wrote:By increasing the recording level, are you meaning to increase the level of "What U Hear"?

The audacity volume control is maxed out so i'm assuming thats what you mean....

If you look in the Windows Mixer or sound card control panel (where you set the "What U Hear" level) you will see that there are adjustments for both recording levels and playback levels. When you re recording from "What U Hear" (also called "Stereo Mix") the recording level depends on both the recording level AND the playback levels. Because it is recording the signal at the sound card output, it will record louder when the output level is louder. You should turn up the playback level for what you are recording (possibly called "Wave out", or "PCM out") and turn down or mute all other channels (such as Microphone, Line, CD, Aux....) This will minimise the noise that is recorded.

Very kewl, thanks Stevethefiddle. It all makes sense to me.