Proper Audio Levels

[Sound Chaser]

FAQ for audio levels: for delivery of final product

-20dbFS (decibels full scale) is the standard scale for all digital audio output and it corresponds to 0db on the old analog view meter. The old system usually had 18db of head room above 0db before clip; therefore -20 corresponds to zero on the old analog format. This is 'average program level, not peak level.

Feature Film: (Full dynamic range) average level -20 with peaks up to zero (in theory) Well produced feature films are probably the best recorded audio tracks of all mediums and are meant to resemble reality. Try to simulate this practice with your final product.

Broadcast TV: -20 with peaks -5db measured over time. Here the lines become blurred as volume wars are common for the purposes of competitive advantage. Some broadcasters allow average levels of -14 to -12. All major broadcast corporations have their 'spec' sheet for deliverables which are available to the public. PBS has the strictest standards and their specifications are available in their 'red book'. If you do not meet the broadcasters 'online' delivery specifications for picture and sound your product will be rejected.
Note: Commercials which sound louder (typically 6db louder) are in fact the same level as regular programming. However, they use a smaller dynamic range resulting in 'perceived" louder sound output.

Music: -6db. Since the digital revolution mastering practices have evolved into a louder is better, no dynamic range volume war. The record industry started the practice of "competitive" loudness way back in the days of vinyl as they
thought that a louder record sounded better and got noticed resulting in higher unit sales

Internet: Typical of the web -- no standard, anything goes.

Commercial video: ??? You tell me.

[strypes]

Good info... a little word up on digital mediums- bit rate corresponds with volume level. ie. If a signal was recorded at 0dBfs, it uses maximum available bitrate (24 bits on a 24 bit recording and 16 bits on a 16 bit recording).

Reason for dynamic compression in broadcast TV, is that people generally do not have dolby certified monitoring at home, and most people do not have good enough speakers capable of simulating any sort of reality, if that's what we are aiming for. In fact, many built in TV speakers cannot handle the dynamic range on feature film recordings.... I'm also keen to figure out what frequency ranges are actually transmitted...

Reason for loudness wars in the vinyl days- because below a certain threshold, vinyls emit hiss and crackles. On tape, there was tape hiss. On CD it was largely obsolete, especially to the extent that they went... songs ended up sounding like wimpless loud muddled mesh of one loud sound- at best, there was careful eq-ing to allow all instruments to be heard. For radio broadcast, if the cab driver was to turn the radio down to a comfortable level, he'd largely ignore most of what's going on air, until this "louder" commercial comes in. The only viable reason for loudly recorded sounds is the maximum usage of bit space (the more headroom you give, just means unused bits of binaries that could have been used for clarity- ever listened to a 6 bit recording?).

The main reason for headroom, is so that you do not clip on recording (this is especially so in location recordings). In post, whenever I'm moving between digital programmes, I make sure I never exceed 0dBs, because I'll be hitting the digital "brickwall" that's commonly known as distortion, because I've run out of bits for the audio. On mastering, i'll lower it to wherever their standards require.

TV stations not making their broadcast standards known to the public? Where I come from, they didn't even make their standards known to people working for them- it always went along the lines of "louder", "softer" until I realized that this particular station prefered their peaks at -6dBfs, not louder, not softer. Whenever I refered to their published standards, i realized they might have been tuned to the analog VU meters. And since I didn't have a VU meter (and digital recordings almost always go by digital full scale/pcm meters), I couldn't be sure if they understood their own standard. Not to mention VU meters respond slower to peaks... Next to that, I only know that they didn't follow their own -10dBfs max permitted peak level standard.

The difference between digital peak points and analog peak points is that 0dBfs is the ABSOLUTE limit of where you are allowed to go before your stuff starts sounding like glass cracking in your ears. At 0dBm on the analog meter, you are just around "saturation" point where the signal sounds 'sweetest'. Going above 0 dBs, doesn't immediately result in crap, unlike in the digital realm, but harmonic distortion which will progressively increase with amplitude until the signal becomes a muddled mess.

There isn't a conversion table between the analog and digital meters because analog signals are based on voltage and digital meters are based on bit samples, they therefore, react differently- VU meters generally react slower to transient peaks. If I recall from one of the final cut training books, there is a rough guide, where if the tape deck was calibrated at 0dbm to -12 dbfs, 0dbfs would roughly correspond to +7dbm (above this line would be where you won't want sounds to go). Another word, is that the -12dB calibration tone, is a new standard set by Apple, and some manufacturers for digital video (for broadcast, the tone is set to -20 or -18 by some manufacturers).