Audio Metering: Everything You Need to Know About Measurements, Standards and Practice for Mixing and Mastering
Introduction
Audio metering is the process of measuring and displaying various aspects of an audio signal, such as its level, frequency, and phase. Audio metering is essential for mixing and mastering, as it provides valuable information that can help you make better decisions about your sound.
Audio Metering: Measurements, Standards and Practice (Audio Engineering Society Presents) Eddy Brixe
There are many types of audio meters, each with its own purpose and function. Some meters are designed to show you how loud your signal is, while others are designed to show you how your signal sounds in terms of its tonal balance or stereo image. Some meters are analog, while others are digital. Some meters are built into hardware devices, while others are software plugins that you can use in your DAW.
In this article, we will explore some of the most common and useful types of audio meters that you should know about if you want to improve your mixing and mastering skills. We will explain what each meter does, how it works, and how to use it effectively.
Level meters
Level meters are probably the most familiar type of audio meter for most people. They show you how strong or weak your signal is at any given moment. Level meters are important for avoiding clipping (when your signal exceeds the maximum level that your system can handle) and distortion (when your signal becomes distorted due to excessive levels). They are also important for achieving a consistent and balanced level across different tracks, mixes, or masters.
There are different ways of measuring the level of an audio signal, and different types of level meters reflect that. Some level meters measure the average level of a signal, while others measure the peak level of a signal. Some level meters measure the level of a signal in relation to a fixed reference point, while others measure the level of a signal in relation to how loud it sounds to the human ear. Let's take a look at some of the most common types of level meters and how they work.
VU meters
VU meters are one of the oldest and most classic types of level meters. VU stands for volume unit, and VU meters measure the average level of a signal. VU meters are analog devices that use a needle that moves along a scale from -20 to +3 dB. The 0 dB point on a VU meter corresponds to a reference level that is usually set to +4 dBu (a common standard for professional audio equipment).
VU meters have an attack and release time of about 300 ms, which means that they take about 300 ms to respond to changes in the signal level. This makes them slow and smooth, and they are designed to approximate the dynamic response of the human ear. VU meters are useful for getting a general sense of how loud your signal is, and they can help you achieve a consistent level across different tracks or mixes.
VU meters are often found on analog mixing consoles, outboard compressors, and tape machines. They are also available as software plugins that emulate the look and feel of the analog devices. To read a VU meter, you should aim for your signal to hover around the 0 dB point, with occasional peaks going up to +3 dB. If your signal goes below -10 dB or above +3 dB too often, you may need to adjust your gain staging or compression settings.
RMS meters
RMS meters are another type of level meter that measure the average level of a signal. RMS stands for root mean square, and RMS meters calculate the square root of the mean of the squares of the signal values. This may sound complicated, but it basically means that RMS meters take into account both the amplitude and the duration of each sample in the signal.
RMS meters are digital devices that use a numerical display or a bar graph to show the level of a signal in decibels relative to full scale (dBFS). Full scale is the maximum level that a digital system can handle, and it is usually set to 0 dBFS. Unlike VU meters, RMS meters do not have a fixed reference level, and they can vary in their attack and release times depending on the design.
RMS meters are more accurate and responsive than VU meters, and they can show you how much energy your signal has over time. RMS meters are useful for comparing the loudness of different tracks or mixes, and they can help you achieve a balanced frequency spectrum. RMS meters are often found in DAWs, audio editors, and metering plugins. To read an RMS meter, you should aim for your signal to be around -18 dBFS for individual tracks, and around -14 dBFS for mixes or masters. These values are not absolute, but they are good starting points for achieving optimal headroom and dynamic range.
Peak meters
Peak meters are another type of level meter that measure the maximum level of a signal. Peak meters are digital devices that use a numerical display or a bar graph to show the level of a signal in decibels relative to full scale (dBFS). Peak meters have very fast attack and release times, which means that they can capture every transient and spike in the signal.
Peak meters are important for avoiding clipping and distortion, as they show you how close your signal is to reaching the maximum level that your system can handle. Peak meters are also important for setting proper input and output levels for your audio devices, as they show you how much headroom you have before clipping occurs. Peak meters are often found in DAWs, audio editors, and metering plugins. They are usually combined with RMS meters or VU meters to give you both average and peak information.
To read a peak meter, you should aim for your signal to be below -6 dBFS for individual tracks, and below -1 dBFS for mixes or masters. These values are not absolute, but they are good guidelines for avoiding clipping and distortion. If your signal goes above 0 dBFS, you will see a red indicator on the meter, which means that clipping has occurred. If this happens, you should lower your input or output level until the clipping stops.
LUFS meters
LUFS meters
LUFS meters are a type of level meter that measure the loudness of a signal in relation to how it sounds to the human ear. LUFS stands for loudness units relative to full scale, and LUFS meters calculate the average loudness of a signal over a certain period of time. LUFS meters are based on a standard that takes into account the frequency and dynamic characteristics of human hearing, as well as the typical listening conditions and devices.
LUFS meters are important for complying with broadcast standards and streaming platforms, as they show you how loud your signal will sound to the listener. LUFS meters are also important for achieving a consistent and competitive loudness across different tracks or masters, as they show you how your signal compares to other signals in terms of perceived loudness. LUFS meters are often found in metering plugins that are designed for mastering or loudness normalization purposes.
To read a LUFS meter, you should know that there are different types of measurements that it can show you. The most common ones are:
Integrated LUFS: This is the average loudness of the entire signal from start to finish. It is useful for measuring the overall loudness of a track or master.
Short-term LUFS: This is the average loudness of the last three seconds of the signal. It is useful for measuring the loudness of sections or segments of a track or master.
Momentary LUFS: This is the average loudness of the last 400 milliseconds of the signal. It is useful for measuring the loudness of peaks or transients in a track or master.
Loudness range (LRA): This is the difference between the loudest and quietest parts of the signal. It is useful for measuring the dynamic range of a track or master.
The target level for your signal will depend on the destination and purpose of your audio. Different broadcast standards and streaming platforms have different loudness requirements that you should follow. For example, Spotify uses -14 LUFS as its target level for music streaming, while YouTube uses -13 LUFS. You can find more information about different loudness standards here: https://www.loudnesspenalty.com/
To use a LUFS meter effectively, you should aim for your integrated LUFS to be close to the target level of your destination platform, while keeping your short-term and momentary LUFS within a reasonable range. You should also keep an eye on your LRA to make sure that your track or master has enough dynamics and contrast. A good rule of thumb is to have an LRA of at least 6 dB for music.
Frequency meters
Frequency meters are another type of audio meter that show you how your signal sounds in terms of its tonal balance or frequency spectrum. Frequency meters display the amplitude or level of each frequency band in your signal, from low to high. Frequency meters are important for identifying and correcting problems in your mix or master, such as unwanted resonances, masking, harshness, muddiness, or lack of clarity.
There are different ways of displaying the frequency content of an audio signal, and different types of frequency meters reflect that. Some frequency meters show you a static snapshot of the frequency spectrum at a given moment, while others show you a dynamic representation of how the frequency spectrum changes over time. Some frequency meters show you a linear scale of frequencies, while others show you a logarithmic scale that mimics human hearing. Let's take a look at some of the most common types of frequency meters and how they work.
Spectrum analyzers
Spectrum analyzers are one of the most popular and versatile types of frequency meters. Spectrum analyzers display the frequency content of an audio signal as a graph or curve, where the horizontal axis represents the frequency bands (from low to high), and the vertical axis represents the amplitude or level (from quiet to loud). Spectrum analyzers can show you both real-time and average measurements of your signal's frequency spectrum.
Spectrum analyzers are useful for analyzing and enhancing the tonal balance of your mix or master. They can help you identify problems such as excessive or insufficient bass, midrange, or treble; narrow or wide frequency peaks or dips; or unwanted noise or hum. They can also help you compare your signal to a reference track or a target curve, and adjust your EQ, compression, or saturation settings accordingly.
Spectrograms
Spectrograms are another type of frequency meter that display the frequency content of an audio signal over time. Spectrograms display the frequency content of an audio signal as a 2D or 3D image, where the horizontal axis represents time, the vertical axis represents frequency bands (from low to high), and the color or brightness represents amplitude or level (from quiet to loud). Spectrograms can show you both real-time and average measurements of your signal's frequency spectrum over time.
Spectrograms are useful for visualizing and editing the dynamics, harmonics, and noise of your mix or master. They can help you identify and correct problems such as clicks, pops, sibilance, plosives, or hum. They can also help you enhance or modify the timbre, pitch, or envelope of your sound. Spectrograms are often found in audio editors and restoration plugins that allow you to draw or erase on the image to manipulate the sound.
To read a spectrogram, you should pay attention to the shape and position of the features on the image, as well as the color scale and resolution of the image. You should also use your ears to confirm what you see on the screen, and avoid making drastic changes based on the visual feedback alone.
Phase meters
Phase meters are another type of audio meter that show you how your signal sounds in terms of its stereo image or phase relationship. Phase meters display the phase relationship between two channels of a stereo signal, such as left and right or mid and side. Phase meters are important for ensuring mono compatibility and avoiding phase cancellation in your mix or master.
There are different ways of displaying the phase relationship between two channels of a stereo signal, and different types of phase meters reflect that. Some phase meters show you a numerical value or a bar graph that indicates the degree of correlation or coherence between two channels. Others show you a vector scope or a polar plot that indicates the direction and width of the stereo image. Let's take a look at some of the most common types of phase meters and how they work.
Phase correlation meters
Phase correlation meters are one of the simplest and most common types of phase meters. Phase correlation meters display the phase relationship between two channels of a stereo signal as a numerical value or a bar graph that ranges from -1 to +1. The value indicates how correlated or coherent the two channels are in terms of their phase alignment.
Phase correlation meters are useful for detecting mono compatibility issues and phase cancellation in your mix or master. They can help you identify if your stereo signal will collapse or lose information when played back in mono. They can also help you adjust your panning, EQ, or delay settings to improve your stereo image.
Phase correlation meters are often found in DAWs, audio editors, and metering plugins. They are usually combined with other meters, such as level meters or frequency meters, to give you a comprehensive view of your signal. To read a phase correlation meter, you should aim for your value to be close to +1 for most parts of your mix or master. This means that your two channels are in phase and have a strong mono compatibility. If your value is close to -1 for any part of your mix or master, this means that your two channels are out of phase and have a risk of phase cancellation. If this happens, you should check your polarity settings or use a phase alignment plugin to fix it.
Goniometers
Goniometers are another type of phase meter that display the phase relationship between two channels of a stereo signal as a vector scope or a polar plot. Goniometers display the phase relationship between two channels of a stereo signal as an X-Y graph, where the horizontal axis represents the left channel and the vertical axis represents the right channel. The shape and position of the plot indicate the direction and width of the stereo image.
Goniometers are useful for visualizing and enhancing the stereo width and image of your mix or master. They can help you identify if your stereo signal is too narrow or too wide for your intended purpose. They can also help you adjust your panning, EQ, compression, or stereo enhancement settings to improve your stereo image.
Goniometers are often found in DAWs, audio editors, and metering plugins. They are usually combined with other meters, such as level meters or frequency meters, to give you a comprehensive view of your signal. To read a goniometer, you should pay attention to the shape and position of the plot, as well as the scale and resolution of the graph. You should also use your ears to confirm what you see on the screen, and avoid making drastic changes based on the visual feedback alone.
Conclusion
Audio metering is a vital skill for any audio engineer or producer who wants to create professional sounding mixes and masters. Audio metering can provide you with valuable information that can help you make better decisions about your sound. Audio metering can also help you comply with broadcast standards and streaming platforms, and achieve a consistent and competitive loudness across different tracks or masters.
In this article, we have covered some of the most common and useful types of audio meters that you should know about, such as level meters, frequency meters, and phase meters. We have explained what each meter does, how it works, and how to use it effectively. We have also provided some tips and guidelines on how to read each meter and what to aim for in terms of target levels and values.
However, audio metering is not a substitute for using your ears and trusting your instincts. Audio metering is a tool that can help you enhance your listening skills and confirm your choices, but it should not dictate your creative process or override your artistic vision. Audio metering is a means to an end, not an end in itself.
We hope that this article has helped you understand audio metering better and inspired you to use it more in your audio projects. Remember that practice makes perfect, and the more you use audio metering, the more you will develop your intuition and confidence as an audio engineer or producer.
FAQs
Here are some answers to five common questions about audio metering:
What is the difference between dBFS and dBu?
dBFS stands for decibels relative to full scale, and it is a unit of measurement for digital audio systems. Full scale is the maximum level that a digital system can handle, and it is usually set to 0 dBFS. dBFS is used to measure the level of a signal in relation to full scale, and it can be positive or negative. For example, -6 dBFS means that the signal is 6 dB below full scale.
dBu stands for decibels relative to 0.775 volts RMS, and it is a unit of measurement for analog audio systems. 0.775 volts RMS is a reference level that is commonly used for professional audio equipment. dBu is used to measure the level of a signal in relation to 0.775 volts RMS, and it can be positive or negative. For example, +4 dBu means that the signal is 4 dB above 0.775 volts RMS.
What is K-metering?
K-metering is a system of metering that was developed by mastering engineer Bob Katz. K-metering uses three different scales of RMS meters (K-20, K-14, and K-12) that correspond to different genres and applications of music. K-metering also uses a standard calibration tone of -20 dBFS that is used to set the reference level for each scale.
K-metering is designed to help audio engineers achieve optimal headroom and dynamic range for their mixes or masters, depending on the style and purpose of their music. K-metering also helps audio engineers avoid the loudness war by encouraging them to use less compression and limiting.
How do I calibrate my meters?
To calibrate your meters, you need to use a test tone or a reference track that has a known level. You can use a sine wave generator or a pink noise generator to create a test tone, or you can use a professionally mastered track that has been measured with a reliable meter as a reference track.
To calibrate your meters, you need to play the test tone or the reference track through your audio system at a comfortable listening level. Then, you need to adjust the input or output gain of your audio device until your meter shows the desired level for the test tone or the reference track. For example, if you are using a VU meter with a reference level of +4 dBu, you need to adjust the gain until your meter shows 0 dB when playing the test tone or the reference track.
What is true peak metering?
True peak metering is a type of peak metering that measures the maximum level of an audio signal after it has been converted from digital to analog. True peak metering takes into account the inter-sample peaks that may occur during the conversion process, which can be higher than the sample peaks that are shown by regular peak meters.
True peak metering is important for avoiding clipping and distortion in the analog domain, as well as complying with broadcast standards and streaming platforms that have strict limits on true peak levels. True peak