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Metering

Metering is the name given to the process of monitoring the volume of the audio you are working on. You could be a great musician, a brilliant presenter, a fabulous DJ, but if you don't know how to make sure everything is at the desired volume, it will all be for nothing.

Audio editing without watching your meters is rather like making a cake without watching how much of each ingredient you put in or how long you bake it for - the recipe may be the best and the ingredients the finest, but it will still end up a mess.

Volume in the Digital Age

Digital audio, like all the other information a computer processes, is made up of 0s and 1s.

CD quality audio is made up of 44100 samples per second, each sample being made up of 16 bits, each of which can either be a 0 or a 1. The way various audio formats store samples is beyond the scope of this article however it is worth noting that storing certain sample patterns will result in an overload of the Digital to Analog audio converters which is known as digital clipping. The sounds that are the loudest without clipping are said to be at 0DBfs. any sound quieter than this is represented by a negative value. A value of -6 DB for example, would be a sound 6 decibels quieter than the loudest sound that can be represented in the digital system. The dbfs scale is rather complex and for those who want all the details wikipedia provides the following:
dbfs

Similarly the quietest a sample can be is represented in binary by a specific minimum value depending on how samples are stored. In the pc-world this is usually 16 or 24-bit little endian but if the above didn't mean any thing to you; do not worry as the storage format of samples on disk is not important to the engineer, only the dbfs scales etc. The minimum sample is the lowest level at which the Digital to Analog converter can detect voltage. Anything quieter than that simply cannot exist at this bit depth.

Turn the background sounds in your drama down too far and they will disappear completely at best or, far worse, sound distorted because they are only being partially resolved as they dip up and down below the least significant bit. This distortion is call quantization distortion. Turn your gun shots and explosions, or your heavy metal guitars and drums up too high on the other hand and there will be no numbers left to create the wave forms' highest peaks, meaning information will be snipped off the top, causing distortion, which is called clipping. The purpose of metering then is to ensure that everything sits comfortably between these two extreme values.

Don't let your Ears Deceive You

While it is true that there is no more important tool in your box than a good set of ears, they are not the most reliable guides when it comes to metering. Sometimes a sound is so short that it does not sound as loud as it really is; sometimes a sound that is too low or high for us to hear can creep into a project and mess up the levels. Therefore, when trying to determine whether something sounds good, i.e. well-balanced in terms of frequency content and stereo imaging, use your ears, when determining your levels, use the meters, which are far more objective.

What metering options are Available?

Determining Item Peak and RMS Level

If you are about to edit an actor's lines or a podcast, the first thing you may wish to do is identify the volume of your audio at its loudest point. There are two ways to do this in Reaper, both involving SWS actions.

  • Having selected the item you want to analyse, press control shift k, which will not only tell you the highest volume of the item, but also its RMS level. this is the volume around which the audio sits most of the time.

For example, if you've recorded a conversation, this may sit comfortably around -18 DB, this would be the item's average volume. However, if someone bumps the microphone, for a split second, the volume may be much higher, say -1 DB. -1 DB Would be the item's peak level, -18 DB would be its RMS level.

If there is a big difference between the peak and RMS levels, you may want to consider taming the peak to make levels more balanced.

  • Having selected the item you want to analyze, press control k. This will not only identify the items loudest point but take you to it, which means you can actually hear what makes the noise. If it isn't something that's useful to the project, you can either delete it or make it its own item and turn it down, either by accessing item properties by pressing shift f2, or by opening Osara's "Item Parameters" dialogue by pressing control shift p.

You could use these methods in conjunction with one another, first determining the numbers with control shift k, then navigating to the loudest point by pressing control k to find out what is making the noise and take appropriate action.

Important Note

These actions tell you the levels for an item, not for a take, track, or indeed your whole project if it is a multi-track project.

If you have overlapping items, adjust the track volume or add effects to a track or take, the values produced by the above steps will no longer accurately represent how loud the audio is.

Metering on the Fly

It is possible to tell how loud the audio coming across a track is at any given moment by pressing j and k. These report the instantaneous volume for the left and right channels respectively for the selected track.

You can determine the instantaneous levels for the left and right channels of the master track by pressing shift j and k.

These actions provide the best way for us to get a picture, albeit a very rough one, of a track's RMS level. By mashing the keys while listening to the audio, you can get a rough idea of where the levels sit at various points and so what the approximate dynamic range is.

This kind of metering, called peak metering, is particularly useful for determining the noise floor of a track. By pressing j and k in the pauses as someone speaks, you can get an idea how loud the background noise is, which is very useful for setting a noise gate to reduce hum or hiss.

The Peak watcher

Using J and K or shift J and shift K can, as we have seen, give a rough idea of RMS levels, but to get an accurate impression of a track's dynamic range, we need to use this method in conjunction with the peak watcher, a powerful Osara feature with a lot of options.

the peak watcher enables us to monitor two tracks simultaneously and can notify us if either of these tracks, one of which could be the master track, reaches a certain level without us having to do anything.

It provides both peak and hold metering. Hold metering is particularly useful because the meter continuously analyzes the incoming audio and displays the highest level it has encountered up to that point. It holds this information either until it encounters a higher level, is reset or for a duration designated by the user.

It can be activated by pressing Control Shift W , which brings up a configuration dialogue and this is arguably the first thing you should do when starting a new project.

The Peak watcher Dialogue

Pressing Control Shift w places you in a dialogue box.

The first item in this dialogue is a combo box, which enables you to select the "first track" that the peak watcher will monitor. This will be the track whose peak level can be discovered by pressing alt f9 for the left channel and alt f10 for the right.

The first two options in the combo are "follow current track", which tells the peak watcher to monitor whatever track you select and "master", which will monitor the master track. Below this, all your projects tracks are displayed in order.

Pressing tab once takes you to the "Second Track" combo box, which contains the same options. The peak levels for the left and right channels of this track are announced when you press alt shift f9 and alt shift f10 respectively.

Next are two checkboxes, which are both checked by default. These dictate whether you will be automatically notified if the volume reaches the designated level for the left and right channels respectively.

Tabbing past these checkboxes puts you in an edit box where you can designate the level at which you want to be notified. By default, this is set to 0.0, the highest volume that digital audio can represent. You may wish to set it to a negative value however.

If you are recording a vocal track, for example, and know that you will be doubling that vocal part, you may not wish the volume of that vocal line to exceed -6 DB, in order to leave room for the second vocal track in the mix.

Once set, the peak watcher will tell you which channel of which of your two designated tracks has reached your designated level and what precise level it reached. Speech will report every single time the level is reached or exceeded so it is important to set this with care to avoid constant notifications.

Tabbing again focusses the "hold Peaks" radio button. By default, the peak watcher is set to hold information about the highest level on a track until it is reset. However, pressing cursor up disables peak holding so that alt f9 and f10 and alt shift f9 and F10 work like j and k for their respective tracks.

Pressing cursor down selects the "for MS" option, following which there is an edit box in which you can type the amount of time in milliseconds you want the values to be held so you can look at them.

Designating a peak hold time could be particularly useful when a track is receiving live input from an instrument or microphone.

Next comes a reset button, which resets the whole Peak watcher to its default values, followed finally by the ever-present OK and cancel buttons.

It is also possible to reset the values for each of the two tracks you have designated individually by pressing alt F8 for the first track and alt shift F8 for the second.

In addition, if you have one of the peak watcher's options set to "follow Current track", changing tracks will reset the values reported by the relevant key presses.

Put it into practice

Now try using what you have learned to set your levels for recording.

Connect your mic, arm a track for recording and monitor it.

Enable the peak watcher and set it to follow the track you have armed and the master track.

Then, as quietly as you can, look at the peak level for that track without making any noise at all.

If you make an unintended noise, a car passes or whatever, you can always reset using the shortcuts described above. The level the peak watcher reports is the highest volume of your background.

Pressing j and k while this is going on will give you an idea of how your noise floor fluctuates.

Now speak or sing into your microphone. Look at the peak levels afterwards, assuming you haven't clipped. -12--18 DB is probably a good region to peak in, although, if you have a noisy setup, the closer you can get to 0 without clipping the better.

Important note that caught me out

you may find that your set-up is too quiet. If you increase the track volume to compensate for this, you will not notice a change in the peak levels reported for that track, but you will notice a change on the master track. This is because, when monitoring live input, the peak watcher shows you the volume coming across the input stage, while raising the track's volume increases the level the track outputs to the master.

Determining Compressor Thresholds

We have already briefly discussed how to use metering to establish the threshold you need for a noise gate. By using the peak watcher, you can work out the threshold you want for a compressor.

Play the track you want to compress while monitoring it with the peak watcher. There would be no point in setting the threshold of your compressor above the level the peak watcher reports for that track once it has played through because it wouldn't do anything.

If you use j and k as well to get a rough idea of the RMS, combining all the numbers will give you the tracks dynamic range, so you will be able to decide how far below the peak level you want to set your threshold and what ratio you want.

Go Forth and Meter

Thanks to the flexible and comprehensive metering options available in Reaper, we are able to balance a whole mix, set up good gain staging and use compressors and noise gates to better effect. Nothing will improve your productions more than a good understanding of these concepts!

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Page last modified on November 01, 2016, at 02:17 PM