Unraveling PA Safety Standards With Sound Advice
The SGSA’s “Guide to Safety at Sports Grounds”, also known affectionately as the Green Guide, describes the Public Address System (PAS) as the “principal means of communication” between the sports venue management and the spectators. It makes it clear that the management is responsible for the “clear, efficient and reliable communications” for safety management and says that as such the PAS should be designed, installed and maintained in full compliance with current British Standards. As the British Standards have recently undergone routine maintenance in this area it, would seem timely to re-visit them.
As of July 2013 the UK has the new European Regulation on CE marking to comply with, EU No.(305/2011). For live safety audio products this has taken the form of EN54 that is having a profound effect on the audio industry in the context of emergency broadcast systems.
While the venue management has overall responsibility for the safety of the public within their venue, they are not likely to experts in audio or speech intelligibility. This puts them in a vulnerable purchasing position, especially when the audio industry itself is struggling to come to terms with the new standards. So, it is a case of caveat emptor, but hopefully this article will shed some light as to which standards to require, what the key elements of the system must be and who to approach for independent advice.
The article references the actual clause numbers of each standard to make it simpler to find out more detail from the standards directly. The British Standards are available for purchase from the BSI online shop: WWW.shop.bsigroup.com
In section 16.14 the Green Guide outlines some of the key functional requirements of the PAS and of real interest and impact are:
- Override facility to bring the PAS back up to full emergency broadcast level if the regular announcements are usually voiced at a lower level.
- Fire Warning - “Emergency use of the public address system as part of the fire warning system requires full compliance with the relevant British Standards”.
- Back up power supply: to allow the system to function at emergency level in the event of mains power failure.
The reason that these are the elements of real interest is that to an electro-acoustic specialist they fundamentally change the importance and classification of the system. The Green Guide is actually describing a Voice Alarm System (VAS), which is a more technically significant undertaking than a PAS. This may seem like semantics since both types of system are essentially delivering audio to the public in the venue but a VAS is designed and installed to have high system integrity which means that it even when seriously compromised, critical messages will be accurately and reliably broadcast.
Following the guidance of the Green Guide the relevant, current British Standards are as follows:
“The design, planning, installation, testing and maintenance of sound systems”
This is an old standard but only by virtue of it’s continuing relevance. It offers really useful advice on audio systems for venue managers, as it explains the different types of PAS and gives guidance on what a buyer should consider and ask for when starting to think about purchasing a system.
“Sound Systems for emergency purposes”
This document remains the British Standard and should be specified as a requirement for any venue VAS, as the Green Guide specifically references, critical life safety, emergency messages.
The key points of the standard that the reader should be aware of are as follows:
4.1: Intelligible information of measure to be taken for the protection of lives.
4g: Failure of a single amplifier or loudspeaker shall not result in the loss of coverage in the zone. This is referring to the need for circuit protection and interleaved circuits that are covered in more detail later in the article.
5.1: 0.7 CIS: This is a measure of speech intelligibility and it equates to 0.50 on the Speech Transmission Index (STI) scale and is usually a requirement for the Local Authority to issue and annually renew any Ground Safety Certificate. The STI metric is readily predicted at design stage by specialist electro-acoustic consultants and then can be proven though measurement during the system sign off process.
5.3 & 5.4: The system shall have automatic fault monitoring and reporting of all equipment and software.
5.5: This clause describes the requirement for a monitored interface with the emergency detection system.
5.6: This clause requires gives the functional requirements of the required secondary power supply.
The Green Guide (10.3d) suggests that the back up power supply should be capable of powering the system for up to 3 hours. However, the British Standard requires that the UPS must provide power for 24 hours in quiescent mode followed by 30 minutes of full level, emergency speech broadcast. It also requires that while on UPS no regular PAS, non-critical, messages or audio is played, so as to ensure that the VAS has enough power should it be required for evacuation.
“Code of practice for the design, installation, commissioning and maintenance of voice alarm systems”
This code of practice is the document that references Voice Alarm Control and Indicating Equipment (VACIE) and lists the 5 types, V1 thru V5. Each type increases in complexity culminating in V5 which is completely bespoke engineered solution that can interface with any or all other venue systems such as CCTV, BMS, AV etc.…
If we consider the sports venue market, there is a considerable range in terms of size and complexity but the VAS that the site requires is usually described by either a V3, V4 or V5.
The key clauses that distinguish these systems from PAS are as follows:
12.1: The requirement for fault monitoring of all system components regardless of whether they are involved in the broadcast of emergency messages of just regular programme material.
12.2.3: Where the venue accommodates more than 500 members of the public there is a requirement for system integrity. This clause specifically calls for interleaved loudspeaker circuits. That is to say that no two adjacent loudspeakers can be fed from the same cable and amplifier channel.
12.24: Contains the requirement of both fire and mechanical protection for all cabling.
14.1: This clause details the design requirements that include evidence of a formal design process and that the loudspeakers and their location must be chosen by a qualified electro-acoustician.
22.3.3. Gives the STI requirement of 0.50 that must be achieved, harmonised with BS60849.
40: This section is important but often overlooked as it describes the required routine testing that must be undertaken to ensure the health and availability of the system. It says that ideally monthly public tests of the emergency messages should be undertaken but these should be no less than quarterly. It also describes the role and remit of the system maintainer throughout a working year.
BS5839-8 also refers to BSEN54, which is the most recent suite of fire detection and alarm standards. This is very significant, as in order to be a VAS from July 2013 only independently certified product may be used to form the system, as it is only through this process that a manufacturer may affix a CE mark.
The minutiae of the requirements are not relevant to this article because all the venue management needs to do is ensure that certified product is installed but for general information the relevant parts of the suite are:
BSEN54-1: 1996 - Fire detection and fire alarm systems: Introduction
BSEN54-3: 2001 - Fire alarm devices - Sounders
BSEN54-16: 2008 - VACIE
BSEN54-24: 2008 - Loudspeakers
Although we often refer to the audio system in a sports venue as a PAS, it is actually required by the Green Guide and the British Standards to be a VAS. There are some serious technical connotations to the term VAS as outlined in this article. Venue Managers should refer to the British Standards when purchasing a new audio system so that they do not erroneously buy a PAS and then find that they are not eligible for a Ground Safety Certificate or worse that in an emergency they have no means of primary communication with their spectators.
The UK is fortunate to have two learned bodies that, have stringent technical membership requirements, whom venue managers may contact to find specialist consultants, manufacturers and installers:
The Institute of Acoustics: for acoustic and electro-acoustic specialists
Telephone: +44(0) 1727 848195
The Institute of Sound and Communication Engineers: for installation and manufacturing specialists
Telephone: +44(0) 118 9542175
Article written by Helen Goddard - AMS Acoustics