Public Address (PA) System

We see public address systems everywhere nowadays. In most places, they are indispensable. These appliances that seem to take up a lot of space wherever they are put up and seem too complicated to use are actually not that complex at all. This article tries to acquaint you with PA systems that you see commonly around you.

What are Public Address Systems?

Simply put, public address systems are systems that are used to transmit messages to a group of people. There are three main functions that these systems do:-

• Accept the sound input from a source
• Amplify the sound to a desired level
• Carry and distribute this amplified sound over to an audience

Hence, a public address system can take a low input of sound and amplify it suitably so that it can be spread over a large area. They might distribute the sound within the same area as the speaker is, or can carry the sound electrically over some distance and then transmit it to an audience located there. In some cases, the sound can be taken from the source, amplified and then carried over to multiple areas at once.

In some modern forms of public address systems, there is also an arrangement for the audience to speak back into the public address system, so that these messages are carried over to the original speaker of the message. Such to-and-fro public speakers are generally used when the source of the sound is away and cannot physically see the audience that the message is passing on to.

Components of a Public Address System

There are three main components of a public address system. These are briefly described below:-

• Mixer – The mixer is the device that produces the right tone of the original sound which is meant to be amplified and distributed. The mixer can change the timbre, level and various other acoustic parameters of the sound. A sound engineer will generally sit on the mixing machine of the public address system and tune it up to the desired sound level. This might be done at the first installation of the public address system, but if the event relies heavily on the sound produced, such as a music concert, then the engineer might sit at the mixer throughout the event and may even keep altering the adjustments according to requirements.
• Amplifier – As the name suggests, the amplifiers amplifies the signals. It increases the volume of the sound that is fed into it from the mixer. It must be noted that the amplifier will not change the quality of the sound in any way; it will only increase whatever signal it is getting.
• Speaker – The speaker is the distributor of the sound that has been amplified by the amplifier. If you are the audience, you will mostly see only the speakers. The speakers can be connected away from the public address system with the help of wires. Taking advantage of this, public address installers will try to put up various speakers among the audience. This helps in proper distribution of sound among the audience. Speakers can be as small or as big as desired, and they can also be placed on the ground, affixed on walls or mounted on the ceilings. Most public address system installers believe that it is the speaker that will decide the ultimate quality of sound produced.

These three components primarily make up the public address system. However, there are several other accessories being used nowadays, such as the microphones to speak back into the speaker. Video monitors can also be attached in conjunction with the public address systems so that people can see each other while speaking. Digital public address systems use computers in order to mix their sound signals.

Where are Public Address Systems commonly used?

Public address systems can be used anywhere. At any place where there is a requirement of transmitting sound over to a large audience, or to a wide area, the public address systems are used. The following are some places where you are sure to find a public address system:-

• Educational institutions and offices – These are not used all the time, but are used when a special announcement has to be made into the classrooms. Each classroom has a speaker of its own, and the source is from a designated room within the institution. A very low wattage is required to operate this public system. A similar system is found in offices.
• Railway stations and similar public places – Public address systems are widely used in making announcements to large groups of people such as those assembled on a railway station or an airport. These speakers are fairly powerful, because they have to carry the sound over the accumulated noises of several thousands of people.
• Concerts – Concerts cannot work without a good capacity public address system. These are the most sophisticated types, because the success of the concert will mightily depend on the quality of sound that is carried over to the audience. Professional people handle these public address systems. Indoor concerts will require thousands of watts of speakers, but outdoor concerts will require anything above 10,000 watts.

There are hundreds of other places where public address systems are used, but these three give a fair indication of the manner they are put to use – for warnings, instructions, explanations and even for entertainment.