Delving deeper into audio visual technology – Part 3

We have been delving a little deeper into audio visual technology, through a number of interview sessions with our technical specialists. We wanted to know what questions or problems our technicians encounter in their daily work. If needed we are happy to add some theory to these answers, because sometimes it is necessary to have a little more background information to understand why a certain solution has been chosen.

We kick off the series with an interview with one of our audio technology specialists.

Topic: Audio Technology

Audio Part 3

At events, we see more attention being given to video, lighting and decoration. The most basic instrument available to us in terms of technology is sound, but this is often neglected. And yet good sound quality is essential to the success of an event. Even if you have a TEDx level speaker, if the presenter can’t be clearly heard by the audience in the back rows, the presentation is worthless. We asked our technicians what it takes to make a meeting or conference a success in terms of considering the influence of the room’s acoustics when it comes to speech transmission.

    1. How are speakers used in a room?

If we look at the set-up of speaker systems, we often see that several speakers are installed, either grouped or distributed along the length of the room. There are two reasons for this:
1.           Proportional distribution of sound throughout the room.
2.           Reducing the effects of sound delay.

Re 1. Proportional distribution:
For an optimal experience, we cover the entire room with a sound that is as even as possible. In doing so, we ensure that the intelligibility is of a high quality everywhere at a volume that is pleasant for all participants. If the sound is not optimally spread, this can lead to a lack of understanding of the speaker, which often results in listener fatigue and irritation. This applies in particular to listeners whose native language is not the spoken language.

Re 2. Reducing the effects of sound delay:
The time between the departure of the sound at the source and its arrival at the receiver is the delay time. With larger distances between source and receiver, the time between sending and receiving increases, which can lead to a situation in which rooms have to use several loudspeakers in order to get a covering sound. In this case, delay is applied, which is actually a (time) correction to compensate for the difference in distance without an audible side effect.

     2. Can you give an example of how delay is applied in a hall?

A hall is divided in 3 zones to cover the sound. At the front, near the stage is zone 1, the middle zone 2 and at the back of the hall zone 3. All 3 zones have a set of speakers to cover the whole room.
If no delay is applied, the sound from zone 1 leaks through to zone 2.  Because the distance from the reproducers /speakers to the receiver in zone 2 is longer than that of the speakers in zone 1, the sound arrives delayed. This is not only disturbing but also confusing for the receiver.
To ensure that the sound in all 3 zones arrives simultaneously, a delay of a few milliseconds is applied, just enough to not hear any disturbing ‘doubling’ of the sound.

     3. What is also often mentioned in connection with audio is the word frequency. What is it exactly?

If sound is seen as a wave, then a frequency is the time between the waves. The time between the waves determines the different pitches in sound, expressed in vibrations per second: Hertz.
One Hertz therefore corresponds to one vibration per second.  However, when sound engineers talk about frequencies, we usually refer to the extremes, a low sound, e.g. the hum of an engine/bass or high sounds such as (horror!) the dentist’s drill. Everything in between high and low is called the mid. Although the frequency range varies in minimum and maximum for each person, human speech falls almost entirely into the ‘mid’ spectrum.
Frequencies in a sound wave can easily be visualized by looking at the vibrations of the cone of a speaker. At low frequencies the cone will vibrate less often but make larger movements and at high frequencies the vibrations are faster and the movements smaller.

Do you have any specific questions about sound?
Just ask us and we will answer them in our next post. For advice you can always reach us by email or phone.