audio-blog

Blog 3 of 3 focuses on the audio mistakes that can happen during a TVC production. Different countries have different standards, and the customer service team at Dubsat have put together some examples of the most common areas for audio mistakes.

1. Frames of Silence

For all Free to Air TV stations, TVC’s are required to have 12 frames of silence at the beginning and end of the TVC, the 12 frames must have vision overlaying it. This helps to create a smooth transition between each commercial, rather than a ‘wall’ of sound (an audio track starting and stopping suddenly). Foxtel are pay TV they do not require 12 frames of silence neither does New Zealand destinations.

2. Sound Levels

To ensure that commercials aren’t too loud or too soft, sound designers and editors are expected to control the sound levels of their material to ensure they comply with your local standards.

For example, Australian OP48 specifies peaking level of -9dB, with averaging around -20dB.

3. Broadcast Levels:

All Australian OP48 broadcast levels should be set to peaking at -9dB, averaging around -20dB

please see below for example:

AUDIO-1

If material however is set at the below levels it will be rejected by the stations:

To High:

AUDIO-2

To Low:

AUDIO-3

The standard that is required now is OP-59 Compliant. This is measured by Loudness, K-weighted, relative to Full Scale (LKFS). This was brought into effect to counter the problem of audio being at the correct level (as per above) but sounding to loud. This is due to the perception of the loudness of the commercial. To correct this issue a mathematical algorithm is used in LKFS to give us the acceptable range of -24 LKFS. CAD in the operational Practice of OP 59 have specified that they and the stations will accept material that is between -23 LKFS and -25 LKFS. For more information please click here.

In the US, the relevant standard is the Commercial Advertisement Loudness Mitigation (CALM) Act as set forth by the Advanced Television Systems Committee (ATSC).

4. Sound Quality

You should also check for quality issues, such as pops, hissing and distortion in the audio track. These artifacts can be introduced during the recording or the editing phase, but tend to be pretty rare as they are usually picked up during the production process.

Audio Pops and Hissing: This happen as air filters through a microphone coil during recording which causes the audio to distort.

Distortion: general distortion occurs when material has been blown up from the original source material, this will sound like ‘crackling’ or a ‘hiss’ sound

Mono: a single audio track that has not been mixed with stereo sound

Dual Mono: when a single track has been duplicated into the left and right channel, dual mono usual occurs when taking material from a post mixed material.

Unbalanced Audio: When the audio has been set with either the left channel is higher than the right channel or vice versa

Wide Dynamic Audio: When the audio cannot be set to peaking -9dB and averaging at -20dB without one being higher or lower than the other. E.g. when the audio is peaking at -9dB but is averaging at -30dB, if you altered the audio to average at -20dB then it will be peaking at -4dB.

Phase: Phasing is essential for any good quality mixed audio.

AUDIO-4 The left and right channels must be separated. If the phase is not set correctly when each channel touches it will cancel out the audio, this will cause the audio to be ‘muffled’ or ‘soft’ it can also cause the audio to become ‘mono’.
AUDIO-5 If the phase is diagonal that means that the audio is unbalanced. AUIDO-6 If the phase is horizontal this will cause the audio to sound ‘soft.

5. Syncing issues

Finally, be on the lookout for out of sync issues, where the audio fails to match up to the visual footage. This can be especially critical when talking is involved: failure to properly synchronize speech with lip movements on screen can be particularly frustrating for viewers.