Indoor Radio System

    

Introduction: see fig.1

Indoor radio systems are the most widely used system from the sound reinforcement systems types, including various types of theaters, stadiums, dance halls and so on.

It is highly specialized, both non-verbal reinforcement,but also for various performances, the use of very high quality requirements, system design should not only consider the problem of electro-acoustic technology, but also issues related to architectural acoustics.

The room´s shape and other factors have a greater impact on sound quality. 

fig (1):Indoor Radio System 

                  

System components: 

This system consists of the three main stages for any other sound system; input, intermediate and output stages which we are previously explained along this course.

The difference between sound system types are mainly in the equipments and devices used in each stage according to the nature of place and the needed sound requirements.

For the indoor sound system, the main devices/equipments in each stage will be:

Input stage:
Microphones (wired and wireless types):
These Mics will be used in theatres, stadiums, churches, Mosques …, etc, but it will not be used in dance Halls and Cinemas where there is no need for it. 

for more information about Microphones, please follow the link.

Intermediate stage:
The indoor radio system will use all the intermediate stage devices/equipments described before in the following links: 

• Audio mixer
• Equalizers
• Mixer amplifier
• pre-amplifier
• Audio amplifier (boosters)
• Monitor unit
• Speaker selector
• Power supply
• Terminal Boards
• Crossover

Output stage:
The indoor radio system will use only the following output stage devices/equipments:

1- Loud speakers:

fig (2): Line Array Element Loud Speaker

Different types of loud speakers are used in this system as Array loud speakers (see fig.2) and multiple ways loud speakers. 

2- Sub-woofers:see fig.3

fig (3): Sub-Woofers

they are loud speakers which are dedicated to the reproduction of low-pitched audio frequencies known as the "bass" which can be controlled to add more sound enhancements.

3- Super tweeters:see fig.4

fig (4): Super Tweeters

they are loudspeakers designed to produce high audio frequencies, typically from around 2,000 Hz to 20,000 Hz, tweeters can be controlled to add more sound enhancements. 

Indoor radio system design considerations for typical building systems: 

Indoor acoustical concerns are quite different than outdoors. For example, outdoor spaces have No-reverberation, reflection or absorption – all of which must be considered for indoor rooms.


In general, the cross-section of the room must be shaped to provide the Optimum sound transmission from the source to the audience, as shown in fig.5 

fig (5): Effect of room shape on sound Transmission

1- Indoor Sports Facilities 

Lots of different types, ranging from small weight training/fitness centers to bowling alleys, racquetball courts, gymnasiums, arenas and stadiums. Quite often the function of the space precludes any acoustical effort. For example, there is very little that can be done to a racquetball court to reduce the echo, and you cannot carpet a basketball court.

Concerns for sound are not usually addressed by the players; rather the roar of the crowd may actually be a stimulus to both the players and audience.

Almost all facilities having spectators need sound reinforcement system to hear announcers.

Large spaces – gymnasiums, arenas, etc. – are often used for other purposes such as concerts, plays, conventions, ceremonies, etc., that have radically different acoustic requirements.

Roof must have STC to reduce loud sounds from audience reaching the neighborhood.


2- Shoebox-shaped Concert Halls 

The traditional European rectangular shape has many successful examples. Generally this design is appropriate for audiences up to about 2000 people. One significant acoustical design feature is a large sound-reflecting surface suspended over the performing area. This adjustable-height reflector allows musicians to hear one another on stage.

All of the walls are not reflective. The side and rear balconies break up the smooth geometry. In addition, sound modulation is provided by niches, reveals and other architectural features.


3- Movie Theaters : see fig.6

fig (6): Complete Theater sound system

Contrary to drama theaters, movie theaters are designed very specifically for amplified sounds. Acoustically, the room shape is not nearly as important as the reflectivity of the surfaces. Theaters usually have large quantities (50% - 100% treated) of sound-absorbing material applied to the walls, upholstery and ceiling to control reverberation since the primary goal is speech intelligibility. Space immediately behind the screen should be very absorptive for good response from the behind-the-screen loudspeakers.


4- Home Theaters

To avoid poor spatial imaging of reinforced sound, small rooms need large areas of sound-absorbing and sound-diffusing materials.


Additionally, these absorptive treatments should be applied to that the average coefficients in each of the room’s principle axes are approximately equal.



Again, I emphasizes that the step by step design for sound systems will be provided at time after knowing all the system configurations, governing laws and rules. So, please keep following.



In the next topic, I will show other sound system configuration type which is “Outdoor Broadcasting system”.