Meter Toolbar

Not Ready for Proofreading -

Meter Toolbar displays the amplitude of audio being played or recorded in the project. It is an easy way to see if the audio is clipped, which results in distortion.

The green bar shows the playback level, and the red bar shows recording level. L is the left channel and R is the right channel.

Gale: Is this getting too "Tutorial"? That said, most of what I've added is not available elsewhere AFIK.

Bill - Nov 22/09: My first impression is that we should describe on the mixer toolbar page how the sliders operate. Our goal here is to document the meters. Of course the two interact, but we need to document how the behaviour of the mixer sliders change according to whether or not they can control the system input and output sliders, and the place to do that is on the mixer toolbar page IMO.

Adjusting playback level

The playback level displayed in Meter Toolbar reflects the amplitude of the waveform. The level of the waveform can also be reduced or increased from that amplitude using the gain slider on each Track Panel, directly affecting the playback meter. Note that the output volume slider on Mixer Toolbar does not affect the playback meter - the purpose of the meter is solely to indicate what the loudness of the project audio would be were you to export it as an audio file.

Bill - Nov 22/09: this is unfortunately incorrect (at the moment). If the playback slider has control of the system volume slider then adjusting the slides does affect the indication on the meters. I've been debating this on -devel, advocating that the meters should always be pre-slider, but this has not been implemented yet.

• Gale: On Windows XP and before, the output slider does not affect the meter and never has. Are you saying that it does on Mac? There should be no debate about this. The output slider does affect the meter on Linux in some circumstances and it's a P3 bug: "If Portmixer uses emulated playback volume rather than native, the Audacity output slider will affect the VU playback meters and these may not then reflect the actual volume level of the waveform".
• Bill: On Mac, if the playback slider controls and mirrors the system output volume slider, the meters are post-slider.

Adjusting and monitoring recording level

Use the input volume slider on Mixer Toolbar to adjust the level of audio being recorded. In the image above, note that the blue lines in the recording meter (indicating the maximum peak level attained) are at about -6 dB. This is a sensible level to aim for when recording, because it gives you headroom to make edits affecting volume afterwards.

Bill - Nov 22/09: Do we want a glossary entry for "headroom"?

• Gale: Yes please. can you do that.

Also, if the recording slider does not have control of the system input volume it is now "disabled" - always jumps to maximum. See the discussion on -devel. This is a good thing since all it did in the past was scale the level indicated on the meters before passing the audio on to the track for recording. The disabling of the input level slider indicates to the user that they need to use their system input volume to control the recording volume.

• Gale: Way behind with reading -devel, but I've seen this happening on Linux, and this will have to be documented on the Mixer Toolbar page.

Monitoring

It is good practice to test the correct input level before recording for real. Monitoring lets you do this without actually having to record and then delete a test track. It also verifies that you are recording the input source you expect. There are two ways to turn monitoring on and off:

• Left-click on the recording meter to turn monitoring on. Click again to turn it off.
• Click on the downward-pointing arrow beside the microphone symbol to display the meter drop-down menu. Choose "Start Monitoring" or "Stop Monitoring" as appropriate.

You will probably want to hear the monitored audio as well as see it. To do this, unmute the playback of your input source in the playback side of the Windows or Mac OS X system mixer. If this does not work, enable "software playthrough" in the Transport Menu.

Bill - Nov 22/09: OS X does not have a "system mixer". The only way to hear what you're recording on OS X is to use software playthrough.

Gale: Then how do you describe Audio MIDI Setup if it is not a system mixer? But you're correct the above is too simplistic for OS X and you'd have to enable Audacity playthrough. Does the Mac-only Audacity "hardware playthrough" work, and is it in the Transport menu as well as "software playthrough"?
Bill: Audio Midi Setup is a separate application that lives in the Utilities folder. Most Mac users will be unaware of it until they encounter it in the Audacity documentation. Audio Midi Setup cannot be used for playing your line input through your system speakers or routing it to your headphone jack.
I've never understood why "Hardware Playthrough" is in the preferences at all - this has not been available since OS 9. It is not in the Transport menu on Mac.
Gale: I know Mac has not supported hardware playthrough for a long time, I was just dog-tired and forgot that when I wrote the above. Why Audio MIDI Setup still has a "Thru" box is another mystery again?? But the point is that Hardware Playthrough was put into Preferences on Mac explicitly to remedy Apple's omission. So what I'm interested in is if you had your external mic connected to mic or line (as appropriate) and enabled hardware (but not software) playthrough in Audacity prefs, does it let you hear the monitoring? I do think this is the place to mention this, but I've seen comments that Audacity's hardware playthrough doesn't always work, so if that's true we should only mention software playthrough here.
My understanding is also that a lot of external devices won't work in Audacity unless set up in Audio MIDI setup, so that's the fail-safe line I take.
Bill: AFAIK the "hardware playthough" option in preferences does not work and I have never relied on it - I ignore it. I can't begin to understand how Audacity could provide hardware playthrough when Apple has disabled it. Even the folks at Rogue Amoeba (strange name, great software) can't do it, and they're Mac specialists. They make a little app called "Line In" [1] that does in software what OS 9 used to do in hardware. Yes the "Thru" checkboxes in Audio Midi setup seem to be permanently greyed out and a search in Help does not mention them.
Yes it is possible that to get some external devices to work one may need to use Audio Midi Setup, but I have not personally encountered any.
Is this the place to get into all this?

What the bars and lines mean

The abbreviations used in the image below are explained in the following text.

• CR: Current RMS Level. The right-hand edge of the lighter part of the bar. This shows the average level of the audio and gives a general indication of its perceived loudness. It relates directly to the amplitude of the light blue shading in the waveform .
• CP: Current Peak Level. The right-hand edge of the darker part of the bar. This shows the current peak level of the audio, and relates directly to the dark blue shading in the waveform.
• RP: Recent Peak Level. These lines indicate the highest peak level attained in the last few seconds. They disappear after playback or recording is stopped.
• MP: Maximum Peak Level. The blue lines indicate the maximum peak level attained during the current playback or recording session. They remain visible after playback or recording is stopped, and are reset when a new playback or recording session is started.
• Clip: Clipping warning. The red lines beyond the maximum value of the scale will appear as soon as the playback or recording level exceeds that maximum. Once they have appeared, they remain visible throughout that playback or recording session. They are thus not an indication of current clipping, but an absolute indication that clipping occurred somewhere in the track. The lines remain visible after playback or recording is stopped, and are reset when a new playback or recording session is started.

To find the exact points where clipping exists in a track, enable View > Show Clipping or run Analyze > Find Clipping....

Gale: re the section below, if you set Audacity to record in mono does the meter ever show anything other than left channel? Is that the point we should be making? If people have stereo input and set recording to mono, then they may either get a mono mix of both channels or just the left. If they want to record two different mic channels from a stereo mixer, set Audacity to record 2 channels. If you want those channels to be mono, use "Split Stereo to Mono" by clicking the downward-pointing arrow in the track name. Which point do we want to make here?

Bill - Nov 22/09: Yes, I think that is correct.

• Gale: Which points are important here- all? Or better, just that if you record in mono only the Left channel of the recording meter displays?
• Bill: OK, I see what you were asking. Tough call. Is it "too tutorial" to include all the points above? I think we want to explain what the meters do, not what the computer's sound control panel might do. On that basis, leave it as it is below.

Meter channels

• When playing a mono track, Audacity sends the output to both left and right speakers. Therefore if you leave the pan slider on the Track Panel untouched, both channels of the playback meter will show an identical level. If you pan towards one channel, then the opposite channel will have its level reduced until a complete pan away from it will remove it.
• When recording in mono (for example, from a microphone), usually only the left channel recording meter will be active, although this will depend on how your computer's sound hardware sends sounds to Audacity.

Bill - Nov 22/09: I think the above would be more accurate if you used the language in the div above. That is, if you set Preferences > Devices > Recording to mono, only the left channel recording meter will have an indication. On Mac using the internal microphone you can record in mono or stereo and in the latter case both meters will indicate. I don't know what happens when you use an external mic plugged into a mic jack.

Undocking and Resizing

Like all toolbars, Meter Toolbar can be undocked, but unlike the other toolbars, it can also be resized. Resizing gives longer scales for the meters and hence a more accurate view of the volume levels.

Bill - Nov 22/09: Not all toolbars can be resized but they all can be undocked. In fact I think the meter toolbar is the only one that can be resized.

• Gale: Corrected, sorry!
  

Bill - Nov22/09: I think the image below has possibly been faked. I can't get the meters to be that narrow. Once the meter has been undocked it cannot be resized horizontally (at least on Mac). I've added a floating meter toolbar in a width that I think is realizable.
The resizing behaviour is strange - try it. Set the meter to minimum width while docked, then undock it. Drag the resize handle down. At some point the meters will change from side-by-side to one above the other. Then when the height of the window exceeds the width they will switch to vertical.

• If the meter is docked, you can resize it horizontally by clicking and dragging the right edge.
• To undock the meter, click the handle on the left edge and drag. You can drag outside the Audacity project window, too.
• To resize when undocked, click on the resize handle that appears at the bottom right of the window and drag horizontally or vertically.

Here is an example of Meter Toolbar, undocked and dragged outside the Audacity project, then resized and oriented vertically using its Drop-down menu:

Drop-down Menu

The drop-down menu lets you change the meter's visual orientation, the scale format and more. You can access it by right-clicking on either the playback or recording meter, or by clicking the downward-pointing triangle in either meter.

Disable and Monitoring

• Disable Meter/Enable Meter: Turns the meter off or on. When the meter is disabled it is gray and does not operate.
• Start Monitoring/Stop Monitoring (recording meter only): Starts/stops monitoring of the input (recording) level without actually recording a track. You can also start and stop monitoring by left-clicking on the recording meter.

Meter Orientation

• Horizontal Stereo: Displays the meter at its default horizontal orientation, with the bars extending from left to right.
• Vertical Stereo: Displays the meter vertically, with the bars extending from bottom to top.

Scale

• Linear: Displays the meter with a linear scale where the maximum level before clipping is 1.0.
• dB: Displays the meter with a logarithmic scale where the maximum level before clipping is 0 dB. This is the default view giving more detail for fainter sounds, corresponding more closely to how sound is heard. The minimum value of the scale can be changed in the Interface Preferences.

Preferences

• Preferences: Opens the Meter Preferences window to set the refresh rate for the meters. A higher rate makes the meter show more frequent changes. Too high a rate can cause audio breakup on slower machines.