So, you got the job! Nicely done! You get that email with the clients instructions, which read something like this:
“Final delivery format must be .BWF stereo interleaved at 48Hhz, 24bit; with an integrated loudness of -14 LUFS, a dynamic range of 10 LU and a true peak of max -0.8 dBTP”.
If you first thought is Huh? then do not fear! This blog is here to help.
As a hobbyist or professional sound engineer you will come across technical terms referring to audio levels and loudness. In some instances those terms can seem like a whole new language. So, to save you a google search we've created some useful information on various terms and meters, that will help you understand your tools and inspire you to create great professional audio.
A Level Meter
is used to monitor levels (RMS [perceived loudness] or peak levels) either as a PPM or VU meter.
Decibels relative to Full Scale. This scale is used in digital systems (e.g. your DAW) and refers to the amplitude of a signal compared with the maximum which a device can handle before clipping occurs. This is usually marked as 0dBFS. You may have notice that the default position for your channel faders is at the 0dB mark.
dB True Peak. The scale is actually dBFS, but measured with a true peak meter. dBTP refers to the peak amplitude of a signal compared with the maximum which a device can handle before clipping occurs. In digital systems, 0 dBTP would equal the highest level (number) the processor is capable of representing. Measured values are always negative or zero, since they are less than or equal to full-scale..
A maximum absolute level of the signal waveform. It measures the peak levels of samples and intersample peaks.
Root mean square. The average power of your audio signal, and close to what your ears perceive as the loudness of your audio.
Dynamics of your audio, or difference between the average “quiet” and average “loud” parts (excluding extremes). Similar to RMS, but based on the LUFS scale which is optimized for human perception.
LUFS and LUFS Meter:
The new standard for measuring audio loudness is LUFS (loudness units relative to full scale). It was developed to enable normalization of audio levels, and matches how our ears actually perceive sound.
The integrated loudness can be understood as the “overall” level of your audio. It’s also good to keep in mind that different meters serve different purposes. You will still need to use your dBFS meters to make sure your signals aren’t clipping.
(also known as a Vectorscope) – Phase plays a particularly important role in mixing as well as mastering as EQ (equalization) may alter the phase of sounds that carry the same frequency content, and cause issues for mono playback systems.
A Correlation Meter
is used in stereo to ensure that the left and right signals will sum to mono without any cancellation of frequencies.
Watch this video for a quick look at the Goniometer and Correlation meters.
So to sum it all up, we measure loudness utilizing specialized meters
Level Meters are real time displays of the signal magnitude of your different audio channels that allow you to monitor the precise signal levels, overall dynamic range; and indicate any clipping in both the digital and analogue domains of your audio channels.
Metering makes the process of setting optimum signal levels quick and easy, warning you of potential problems before they occur.
Without going into the details inherent to EBU (European Broadcast Union) R128 , in the US, broadcasters must adhere to a similar loudness standard called ATSC A/85) it's important to know that these are means to measure, and thus standardize, perceived volume. The major players in the industry (Spotify, iTunes Radio, as well as many TV & Radio stations) comply to these standards, and as a professional or even hobbyist mastering or mix engineer, you must take it seriously.
Each platform is using a standard loudness level so their content can be "standardized". This standardization means consistent loudness across each track on the streaming platforms. Thanks to the LUFS measurement meters we now are able to reference content to industry standard prescribed levels.
Below are the new Loudness reference levels for various platforms.
Itunes Store = -12LUFS
Itunes radio = -16LUFS
YouTube = -13LUFS
Spotify = -12LUFS
Speech = -23LUFS