METERS: DBfs (PPM and RMS) vs VU vs DBspl

DB fs (full scale) meters – software and hardware digital meters that measure signal strength in software or a hardware device (examples below)

DBfs Meters – Peak Vs RMS There are two standard types of DBfs meters: PPM – Program Peak and RMS – Root Means Square

PPM level metering will measure sudden changes in level and altering you of digital overloads, which is crucial to avoid clipping the signal. Peak metering will NOT give you a proper indication of perceived loudness. PPM meters are better for monitoring transients and are often used to find that are spiking so you can make adjustments that keep them at more consistent levels.

Digital PPM or Peak Program Meters can help you get a sense of the dynamic range of your mix by displaying the maximum level of an audio signal’s waveform. Peak metering is designed to respond quickly so that the meter display reacts in exact proportion to the voltage of the audio signal. Peak meters are also very useful for alerting users when potential clipping distortion occurs caused from the signal spiking over 0 dBFS.

NOTE:

The loudest program materials (i.e. whatever represents the loudest thing in the scene/mix) should be dancing around -12 DBfs (ppm). Giving you head room for more dynamic mixes.

When you calibrate your monitors this is also where PINK NOISE will sit when monitoring PPM.

RMS metering will give you a more accurate impression of perceived loudness because this type of meter measures levels slower than a PPM meter and will display an ‘average’ level rather than the instantaneous peaks. This type of metering is either commonly used to match loudness levels with commercial masters or used to identify sounds that are eating up headroom and not letting the higher frequencies cut through the mix such as bass notes or a kick drum. For example, an RMS meter could be helpful at identifying a heavy sub bass that may be dominating your mix which can affect the clarity and impact of other sounds.

RMS (Root Mean Square) metering is a more accurate way to determine the loudness of your mixes. RMS meters essentially emulate VU meters commonly found on analog consoles and are designed to give a better impression of perceived loudness by displaying the average output level calculated over a short period of time. An RMS readout will typically display lower than an equivalent peak meter because it measures the amount of energy in the waveform and averages the peaks into the overall loudness which is a more sustained level compared to fast changes in level.

NOTE:

The loudest program materials (i.e. whatever represents the loudest thing in the scene/mix) should be dancing around -20 DBfs (rms). Giving you better sense of perceived loudness over time.

When you calibrate your monitors this is also where PINK NOISE will sit when monitoring RMS.

VU (volume unit) meter analog meters that measure signal level (0vu = -20db fs/- 18db fs) (see example below)

A Volume Unit Meter is a metering unit to measure a signal level volume. It has a slow response and ignores the signal peaks (300 milliseconds of integration time). It works in a similar way to the human ear. Due to its similar behavior, VU meters are useful when in the mixing phase of a project.

VU Meter Calibration:

Calibrating a VU meter plugin in the digital world is easy, get a dBfs reference to match with 0VU (0VU means when the VU needle is on zero).

Ex: If you choose -18 dBfs = 0VU, you will get a 18 dB of headroom approximately. This could be -20 dbfs, etc. depending on what stardard you are using.

DB spl Measure of pressure (i.e. the condensation and rarefaction of sound in air - via playback/speakers/sound source) (i.e. real sound in a real space NOT a signal in software or hardware)

Standard for studios/sound stages are:

79dbSPL for Small Theater/Mixing Spaces 83dbSPL for Mid Sized Theater/Mixing Spaces 85dbSPL for Large/Standard Theatrical Spaces/Mix Theaters

This is measured by playing PINK NOISE out of a daw (digital audio workstation) and speakers at -20 dbfs (rms) with an SPL meter set to:

C-weighting/Slow Response

And adjusting the volume control on your speakers (or master volume) until they play back at:

79dbSPL for Small Theater/Mixing Spaces 83dbSPL for Mid Sized Theater/Mixing Spaces 85dbSPL for Large/Standard Theatrical Spaces/Mix Theaters