DAWs provide many great advantages in audio production over old school analogue workflows. Besides being immensely instinctive environments in which to work quickly in they also make it very easy for us to be able to visually interpret what audio is doing in certain audio applications and processes. Without us having the ability to see audio we would find it near impossible to tune a vocal, conform a complex drum pattern to the grid, surgically remove an unwanted sound from a dialog recording and more.
In this article we explain several different ways that audio is graphically represented in DAWs and a number of different tools from a range of developers to help you understand not only what these visuals tell us but to show you what they are for and how to interpret these graphics and displays to help you. This article isn’t a deep physics lesson in audio, instead we try to explain each of these points as practically as possible.
We are going to kick off this article with two of the most basic forms of how audio is displayed in the digital domain followed by some more complex displays:
Waveform views are the bread and butter of any DAW. You most likely stare at these for hours, perhaps taking them for granted as you chop them about on your timeline. Without waveforms, we would find it much more difficult to perform the most basic of audio edits, which is a mainstay of any DAW. With a quick glance of a waveforms, we can get a sense of the performance style and dynamic range, which is useful for a number of things such as working out where we are in terms of time in a song. Waveforms can also show us basic discrepancies in a performance such as small knocks and thump sounds between vocal takes or clipping if a signal was recorded too hot and help us to get clips in time or in sync.
Beside being an essential means of visually interpreting audio, waveforms also enable us to be able to edit, move and remove sections in seconds. Without detailed waveform views we would find it almost impossible to slip out of time sections within a performance into the pocket. We would also struggle to line up duplicate clips and edit out unwanted noise. This section may seem somewhat obvious but we felt it was important to include this essential audio display to start this topic to remind us all how important waveform displays are in audio production.
Level meters are the second bread and butter way of visualising and interpreting audio, which you find throughout any DAW. Level meters come in all shapes and sizes from basic scale levels you find in mixer windows through to analogue inspired VU meters with bouncing needles. They help us with two main aspects, one for getting sound into a DAW to set appropriate signal levels when tracking as well as for meeting specific delivery specs when outputting our mixes.
DAW mix windows typically display signal level on a decibel (dB) scale in real time when the DAW is in playback or record. They display signal level for each channel may it be mono, stereo or surround by a colour determined by the DAW (Example: green for Pro Tools, blue for Logic Pro X). Typically when signals approach 0 dB the level in the meter will change colour to yellow and beyond 0 dB the level turns red symbolising that clipping has occurred. For more on using level meters in a DAW check out our article Getting To Grips With Pro Tools Part 6 - Recording Levels. Don’t worry if you aren’t using Pro Tools, the principles in this article will apply to any DAW.
Level meters can display a variety of different meters which are all suitable for certain audio applications. Pro Tools provides 17 different metering modes. To learn about each of these, check out our article Tutorial - Understanding The Advanced Metering In Pro Tools.
The other area that audio metering is really important for is the final delivery stage to enable us to deliver our mixes to the appropriate spec for the customer. In both music mastering and broadcast workflows, the there will be a delivery spec that you are required to deliver to. It may be a maximum peak level, or often these days loudness and true peak levels. The key here is to have the correct meter for the delivery spec you are working to, otherwise you will run the risk of having your mixes rejected.
Loudness is becoming the de facto standard for delivery specs for more and more broadcast. OTT and music master deliveries. The specs are usually built around the BS1770 standard and measure loudness in LUFS or LKFS, they are 2 names for the same measurement. For broadcast or OTT workflows, check out Mike’s excellent Understanding Loudness course…
If you are delivering music mixes to streaming services then do check out this series of tutorials…
You can find spectrum analysers in EQ plug-ins like the Fab Filter Pro Q2 or as standalone plug-ins like Visualizer from Nugen Audio or Insight 2 from iZotope. They simply show us the amplitude of any given input signal, it may be a vocal or an instrument, across the full frequency range from 20Hz to 20kHz. They can help us to determine how to set an EQ or filter curve on a track as well as show us the results of our EQ’ing efforts. On the flip side, the ballistics of spectrum analysers can negatively influence our EQ decision making which can lead us to over-egging the pudding.
For example, spectrum analysers are great for quickly finding resonances that require a touch of subtractive EQ. For broad brush applications of EQ you are better off not looking too deeply into what the analyser is showing you as it’s better to apply wide bands with your ears guiding your instincts rather than your eyes drawing imaginary curves through the ballistics. Check out these 2 reviews on the Nugen Audio Visualizer 2 plug-in and iZotope’s Insight. Both of these have a range of the tools covered in this article, not just spectrum analyzers…
In this show and tell video review Mike takes a tour around the Visualizer 2 plug-in from Nugen Audio. Watch and see what he finds and how it could help you visualize your audio.
In this video, Mike offers a show and tell review of the metering & visualisation plug-in from iZotope. In September 2018 iZotope released Insight 2 which added a number of options including an Intelligibility meter.
Spectrogram Waveform Displays
The king of spectrogram displays has to be the audio restoration software iZotope RX. it does take a little time to get used to the spectrogram and how to interpret it but in the case of the example above, the brighter the orange, the louder those frequencies will be. You have frequency on the vertical axis and time on the horizontal axis and like the waveform on a DAW you can zoom in to see things in more detail.
The easiest way to understand how a spectrogram works is by seeing it in action. Check out these two tutorials, one using Visualizer from Nugen Audio and the other using iZotope RX…
As you can see from these tutorials, the spectrogram display is an essential part of tools like iZotope RX. It would be fair to say that iZotope RX wouldn’t be the excellent tool it is without the spectrogram window to display very clearly what we are listening to and help us to be able to surgically remove problem areas of audio.
A histogram for any kind of data is defined as ‘an accurate representation of the distribution of numerical data’. There are two types of histogram in common use in audio visualizers and Nugen Audio VisLM loudness meter has the both so is a good place to start. In the centre section of the VisLM2 window we have the first one, the loudness history view, which displays the historical loudness and true-peak clip values over time.
The second is the loudness distribution display and represents the distribution of loudness measurement within the Integrated loudness measurement, which you can see on the left hand side of the images above. You also get the distribution type of histogram in a number of plug-ins like Maxim from Avid and a slightly different version in its predecessor, the Digidesign version of Maxim. in these 3 cases the histogram shows how the loudness is distributed across the dynamic range. Finally on the right we have a 3rd type, which can be found in the DeClip module in iZotope RX, where it helps to establish the clipping threshold by seeing where the peaks are in the audio level.
Vectorscopes & Correlation Meters
These two displays often go together as they both in their own way help to visualize stereo width. In the image above, the main part is a vectorscope, which shows where across the sound energy is being distributed across the stereo image, which are useful for visually seeing if there are elements of a mix that are too wide or narrow. There are two views in the vectorscope…
The Lissajous view plots the left channel on the x axis and the right channel on the y axis but the whole graph is rotated by 45 degrees so that the x and y axes are at 10 o'clock and 2 o'clock with halfway in between (the centre of the stereo image) is at 12 o'clock.
The Polar plot presents only the positive half of the Lissajous but offers more display options and a stereometer which displays information about the stereo position of the signal, which in the example above shows a push to the right, that also indicated by the stereo balance meter underneath the vectorscope displaying ‘R9’.
Phase correlation meters show us the similarities between the left and right channels of stereo image and are used to show if a mix has mono compatibility issues if folded down from stereo to mono. The meter position represents the correlation between the stereo channels. A value of 1 indicates 100% correlation (mono), 0 indicates no correlation and –1 indicates 100% negative correlation (out of phase signals).
Different tools display vectorscopes and correlation meters slightly differently. Check out 4 tutorials on 4 different tools, the free iZotope stereo imager which has a vectorscope in it, the Nugen Audio Visualizer 2 plug-in, the RTW Loudness and Mastering Tools suite and LEVELS from Mastering The Mix…
Pitch graphs in tuning plug-ins such as Antares Auto-Tune Pro and Celemony’s Melodyne are not too dissimilar to how MIDI notes are presented on piano rolls. Melody lines of performances are represented by a thin pitch line over the white and black notes of a piano graphic which also shows nuances such as vibrato depth and rate. We use pitch graphs to nudge parts of an out of tune melody into pitch. Like spectrum analysers, the visual nature of pitch graphs can easily lure us into over processing. Often small adjustments in pitch here and there are all a track needs to be improved.
In Melodyne’s pitch graph you see large yellow to red shapes around the pitch lines. These are mini waveform views representing a note’s amplitude. Each of these waveform strengths can be altered along with the pitch correction tools to sculpt the perfect sounding vocal.
In plug-ins such as Antares Auto-Tune Pro and Waves Tune Real-Time, pitch displays show us what notes in a performance are being processed at that moment. Pitch displays come in a few different styles such as the central display in Auto-Tune as well as keyboard displays with the keys changing colour showing us what pitch is being played in real time.
Keyboard pitch displays are useful as we can use these to easily deselect notes within a scale which in essence ignores those notes forcing the tuning to the next nearest note. Large dial like pitch displays are handy as they show us how much of a melody is out of tune in regards to the song’s scale as well as giving us a sense on how aggressive the tuning effects are.
There are 7 different types of audio visualizer tools that are designed to give you rapid access to the information you need to fully understand your audio. In their different ways they can provide a great deal of detailed information, coupled with options that allow a high degree of user customisation. Yes, audio is about what we hear and you can go overboard with visualizer tools and end up listening with your eyes rather than your ears. That said, as long as you treat them as tools, as part of your broader toolkit then these audio visualizers can provide a lot of useful information and display the audio that you are working on in a clear and helpful way.