Speech transmission intelligibility

1st October 2021 By: Terry Mackenzie-hoy

It’s almost a given. At any function, on any TV broadcast, we will hear somebody speak. More likely than not, the speech will come across with an echo, which will make it hard to understand. Not impossible, just hard.

But we concentrate, we listen, and we follow what is being said. It should not be so. The echo we hear is, in fact, the symptom of a public address (PA) system that is poorly set up, badly aligned and basically ill functioining. This happens today, right now, in the smart computer and everything fully communicating age. Many PA systems are just poorly designed and badly set up. The reasons for this are many. Most commonly, the sellers of PA systems want to make money. Lots of it. Consequently, when they offer a PA system, they offer a whole lot of techno twaddle whose description sounds amazing but is, in fact, just twaddle. A primary example of this is the new Cape Town International Stadium. This cost R4.4-billion, or a cool $300-million. The PA system is rubbish. You can’t hear what is being said. The developers noted this during construction and gave the PA system suppliers R1-million more. Which made it worse.

In many of our airports (not Cape Town or King Shaka) the PA system is unintelligible.

Okay, so who cares? Well, if an emergency evacuation is required, somebody should care. People could get injured. Now it happens that PA systems can be tested to see how intelligible they are. Various suppliers of sound-level meters have developed test systems which allow the intelligibility of the PA system to be tested. A signal is generated and played through the PA system. The person holding the test meter then moves through the venue to see how well the signal measured by the sound-level meter compares with the signal being played on the PA system. The result is noted and, if all is well, the owner is comfortable that the venue is safe. This test is called a Speech Transmission Intelligibility Test for PA Systems (STIPA). Oddly enough, the owners who mostly care about this all are not in South Africa. We have a testing system, such as I have described (so do others, so don’t feel restricted to us) but we have done most of our tests at venues which are not actually in South Africa – Botswana and other African countries. We did, in point of fact, do a STIPA test at Cape Town International Stadium and it failed miserably. As I mentioned, not much was done about it.

There is no regulation – nothing in the Occupational Health and Safety Act – which stipulates that a public address or emergency evacuation system should be intelligible to the persons in the venue. This is in contrast to the UK, the US and other European countries. One imagines that the reason for this is that there is no imperative for this to be so; there has not, as up until today, been a disaster that can be attributed to a defective PA system. Members of the public are quite used to the fact than many PA systems cannot be understood anyway and so just shrug the matter off. In many of our airports, we just realise that any announcement which begins “Announcing the . . . ” is just an invitation to look at the flashing lights on a departure information board. We proudly say that we have ‘silent airports’ because, yes, it is nice to have a quiet venue free of announcements, but I at times wonder if this all arose out of the fact that many of the announcements were so meaningless that an alternative had to be found. All this brings us to the Newlands cricket ground. Here, my friends, the announcements are clear, crisp and understood. I know this because in my earlier years I designed the system. As long as it has not been tampered with, it is an example of what’s possible. Other systems should be the same.