---
title: "Clearcast — UK Television Advertising Clearance"
description: "Clearcast's technical specification for UK television advertising: integrated loudness to EBU R128 at −23 LUFS, and a phase-coherence requirement that mean phase must not fall below −0.95."
canonical_url: "https://elephantaudio.pk/reference/clearcast"
type: "Article"
date_modified: "2026-09-19T02:06:04.588Z"
publisher: "Elephant Audio"
publisher_url: "https://elephantaudio.pk"
source_kind: "published-standard"
source_url: "https://clearcast.co.uk/wp-content/uploads/2024/07/Clearcast-Library-Technical-Specification-Guide-v1.6.pdf"
source_fetched_at: "2026-09-19"
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---

# Clearcast — UK Television Advertising Clearance

## What does Clearcast require from an advert's audio?

Clearcast clears UK television advertising. Its technical specification sets integrated loudness to EBU R128 at −23 LUFS, and adds a phase-coherence requirement that mean phase must not be below −0.95 — an automated check that appears in no EBU recommendation and rejects mixes that pass every loudness test.

−23 LUFS integrated loudness (stated as EBU R128) · −0.95 mean phase floor (must not fall below) · v1.6 specification version (Clearcast Library Technical Specification Guide)

What Clearcast is, and why its spec is not optional:
Clearcast clears advertising for the UK commercial broadcasters. An advert does not reach UK television without passing through it, so its technical specification functions as a delivery requirement regardless of what any loudness recommendation says.
On loudness it defers to the European standard: integrated loudness is stated as EBU R128, −23 LUFS. What makes the document worth reading is the requirement that has no equivalent anywhere else.

⚠️ The requirement that is in no loudness standard:
> "Phase Coherence: Mean Phase must not be below -0.95" — Clearcast Library Technical Specification Guide v1.6. Read 2026-09-19

Why a phase floor catches mixes that measure perfectly:
Loudness measurement is indifferent to phase. A stereo mix with a polarity-inverted element, an over-wide stereo plug-in on a bus, or a mono element duplicated and delayed can integrate to exactly −23 LUFS, sit under every true-peak ceiling, and still fail this check.
The consequence is not academic. A mix with poor phase coherence partially cancels when summed to mono — which is what happens on a phone speaker, a television with a single driver, and a large part of broadcast distribution. The gate exists because the audience frequently hears the mono sum, and a number caught it more reliably than an engineer listening in stereo would.
The practical answer is to check the mono sum before delivery rather than after rejection, and to treat aggressive stereo widening on a full mix bus as something to justify rather than default to.

Sources:
- Clearcast — Library Technical Specification Guide v1.6 (PDF) — The loudness and phase requirements here. Read 2026-09-19.: https://clearcast.co.uk/wp-content/uploads/2024/07/Clearcast-Library-Technical-Specification-Guide-v1.6.pdf
- Clearcast — technical specification help centre — Clearcast's own index of the current specification.: https://help.clearcast.co.uk/en/article/the-library-full-technical-spec-download

## Frequently asked questions

### What is mean phase, and why would an advert fail on it?

It is an automated measure of how coherently the left and right channels relate. A mix can hit every loudness figure and still fall below −0.95 if it carries a polarity-inverted element, heavy stereo widening on the mix bus, or a duplicated-and-delayed mono source. The check catches what a stereo listen does not.

### Does Clearcast set its own loudness target?

No — it states integrated loudness as EBU R128, −23 LUFS. The loudness requirement is the European one; the phase requirement is Clearcast's own and has no equivalent in the EBU recommendations.

### How do we avoid a phase rejection?

Check the mono sum before delivery. If elements disappear or thin out when the mix is collapsed to mono, phase coherence is the reason, and it is far cheaper to find in the mix than in a clearance report.

## Related

- [The loudness supplement written for adverts](https://elephantaudio.pk/reference/ebu-r128-s1/raw)
- [The European recommendation Clearcast cites](https://elephantaudio.pk/reference/ebu-r128/raw)
- [Audio for ads and digital campaigns](https://elephantaudio.pk/services/ads-digital/raw)
- [Which delivery number applies to your spot](https://elephantaudio.pk/guides/broadcast-loudness-specs/raw)

## Studio

- **Studio:** Elephant Audio — Lahore, Pakistan
- **Founder:** Abu Bakar Zahid — Founder, Managing Director & Music Producer at Elephant Audio
- **Website:** https://elephantaudio.pk
- **Contact:** abubakar@elephantaudio.pk