Public Address System - Assignment Example

? Public Address System The venue in Manchester where I have chosen to host the live event is the Manchester Evening News Arena. This is an indoor arena which was specifically constructed to host sporting and music events. It has a sitting capacity of 19950 individuals. The arena is located in Hunts bank in the City of Manchester and was a key factor in the Manchester City’s bid to host the Olympic Games of the years 2000 and also 1996. The venue hosted the 2002 Commonwealth games. The arena is a huge sports complex with a 105 meters truss roof spanning its top. In an effort to increase the level of insulating sound in the arena, the material that was used for construction is reinforced concrete. It is among the few European arenas which is featured with a seating of 360 degrees. The arena is one of the busiest in the globe. It has millions of visitors streaming in every year to attend live music, comedy, tours, musicals and sporting events. A public address system is a system of electronics which comprises of a loudspeaker, an amplifier and a microphone and I geared towards amplifying the voice or sound of the speaker or recorded audio so as to permit effective communication with a large group of people. Public address systems play a very key role in the society. They are used in several places where their use is almost virtually indispensable. These include noisy places such as railway terminus, market places, churches, airports, harbors and the like. They are used to facilitate numerous functions which include campaigning in political rallies; reaching to large multitudes; advertising and making sales in crowded places; making open air prayers among Muslim societies and the like. The Manchester Evening News Arena mostly uses or requires a public address system for functions such as announcing the performer in the next music or sport event; announcing the scores in a sports activity; transmitting the address of guests in attendance to the occupants of the arena; making announcements regarding procedures of departure or refreshment among several others. Concert The concert for which this design I slated is Rock band concert which shall be graced by the popular Aerosmith band. They shall be entertaining an expected huge crowd of people who shall come out to party given the reputation of the band. It is expected to be an all entertaining show piece which shall be in the form of a live music performance by the band. The Arena is very big and with the huge crowd that shall throng it, the Public address system that is necessary for the concert has got to be top notch. Major Design consideration The major factor of consideration in the design of a public address system is the space and pathway for the wiring lines and the public address system equipment. The design should create clear cut path ways where the cables shall pass so as to avoid human interference with the system. In the event that the cables are laid in the paths where there is constant traffic, there is a high chance that the traffic might stumble upon the wires and accidentally cut one, a number of or all of them. In this case, the public address system shall miserably fail (BARNETT, WOODGATE, JONES, & INGLIS 1991). What is worse is the fact that it might take a very long time to identify where the problem is before fixing it. This shall cause a delay in the schedule and a total mayhem in the arena. The best design of public address system for the arena is thus one which has all the cables buried in pipes underground and in concrete walls or pillars. The speakers and equipment should also be connected in parallel and not in series. Equipment connected in series have the tendency of all failing in the event where one of them fails. On the contrary, equipment connected in parallel keep working even after one of them or a number of them have failed. Sound on stage The stage is where a bulk of the activities shall be taking place as it shall be focus of attention. All eyes shall be on the stage and of course so shall be all the ears. It is important that the level of sound on the stage should be kept relatively high. The performers on the stage shall feel all hipper and jamming if the stage is kept loud enough. This shall be reflected in their performance and it is instrumental in seeing to it that the concert is a success. Nevertheless, it is also vital to ensure that the sound level in any part of the arena is kept within the constraints of safety and health consideration. The stage being essentially the loudest part of the concert should not have sound levels that cause damage to the ears of its occupants. It is scientifically known that a short time exposure to sound levels of 140 decibels causes permanent damage to the ear. It is also known that at a relatively lower level of 125 decibels, pain begins to be felt in a human ear. Based on this, and in the spirit of keeping the stage the loudest, the sound level on the stage shall not exceed 107dB. Frequency The human ear has a hearing range which is described by the range of frequencies over which sound can be heard. This has been scientifically determined to be between 20Hz and 20,000Hz (PETTO & GODFREY 2007). Frequencies below 20Hz are practically inaudible and those above 20,000Hz are dangerous. It is also known that the hearing range varies from human to human. Age is a major factor in the variation of hearing range frequencies from individual to individual. The older one gets, the less he can hear the very high frequencies. The concert shall be thronged largely by the youthful population but a couple of the aged people are also expected to grace the function. In this regard, the range of frequency has to be from 30Hz to 18KHz and not be exceeded Back stage sound level From time to time, there shall be consultations and important conversations that shall need to take place within the arena as the loud performances are on-going. The stage shall need to be kept active at all times with one activity after the other. This implies that in readiness to take up the mantle at the stage, there should be a team very close to the stage doing their preparation and this has got to involve an audible conversation. The best place for this is the back stage, and in that regard the back stage needs to have a much lower sound level. Keeping the level too low might also put it at the risk of being drowned with the levels of sound on the stage completely and hence at the back of the stage frequency level shouldn’t drop below 10dB. Speakers The speakers are the output components of the entire PA system and they shall have to be top notch. The Speakers I am using for this concert are the J-series speakers. The J-8 series and the J12 series are loudspeakers and they shall be instrumental in projecting the sound to the far flanked areas of the arena. The J-SUB on the other hand is a cardiod subwoofer that marvels the sound and makes it more melodic as it is acoustically matched and mechanically compatible with the J-series loudspeakers. In order to have a variety of combinations that supplement the system, the J-INFRA subwoofer shall be used. The concert shall use a total of 18 J-SUB speakers; 6 J-INFRA speakers; 60 J-8 series speakers and 2 J12 series speaker. Amplifiers The amplifier that shall be used for this concert will be the D-12. This is compatible with the j-series speakers and shall be effective in getting the sound amplified to the designed frequencies and sound levels. The amplifier has a unique design which incorporates analogue as well as digital inputs and hence effective for the principle of flexibility just in case anything happens to the initial digital input system which shall require a quick change over to analogue input. The amplifier also has remote control provisions which make it an effective and convenient system of operation. It does not require long cables or physical presence to do change overs and manipulations in the set levels of amplification. It is also incorporated with an internal cooling system which makes it viable to stand long term performances like it is going to be the case in the concert. A total of 17 D-12 amplifiers shall be used for the concert. Microphones The microphones are the audio input devices for the public address system and they shall be used extensively with the performers on the stage. Performing with a microphone on the hand is challenging enough and dealing with a cord attached to the microphone from some external source is simply put, tedious. In this regard the concert shall make use of wireless microphones to make the performance much more convenient and hence more enjoyable. Microphone stands shall be provided as well especially for the band members who shall be doing instruments. It is impossible for one to carry a microphone while on a guitar or the drums. Power calculation (Watts*1.4)/ Volts J-12 + j-8 will use D-12 which is 8 Ohms J-Sub will use D-12 which is 4 Ohms 1 * Sub = 1 * D-12 = 4 Ohms The design of the power necessary for the Public Address system was made on the basis of safety and power ratings of the equipment. The most important element in the consideration of safety is the current supplied. In the arena there are very many people and this makes it possible for at least one or a number of people to somehow come in contact with the cables. In this regard, it is vital that the current in the cables is kept as low as possible as this is responsible for electrocution and subsequent injury or even death. Equipment Current drawn Amps Quantity needed Total current needed (Amps) Amplifier 2.96 17 50.4 J-series Speakers 1 86 86 Microphone 1.3 7 9.1 145.5 From the total current drawn, given that voltage in the UK is delivered at 230 Volts from the mains; The power required shall be 145.5 * 230 = 33,465 Watts POWER = (33465 * 1.4)/ 230 = 203.7 AC power supply shall be required to avoid power loss. Based on the mains supply in the UK, the frequency shall be 50 Hz. The supply shall also be single phase for the sake of safety. In order to avoid interference, the electrical channel for lighting shall be made separate from that of the PA system. This is because interference causes some form of undesired buzzing sound in the PA system. Conclusion The Manchester Evening News Arena is a very large ground where several music and sporting events take place. Designing a public address system for it takes a lot of elements into consideration. These are very key elements which on proper consideration produces a state of the art design for the public address system of the arena. The public address system should be very dynamic. The equipment used should also be of high quality. It is also essential to ensure that the system is very safe. The crowd size should be considered so as to design a suitable public address system. It is also important to see to it that the equipment that are used are not only able to synchronize with each other, but that they are supported by the wiring system that is used. The space and pathway for the wiring lines and the public address system equipment should also be sufficient and out of reach to the public. Another key element of design is the performance of numerous sound checks on the system to ensure that it is perfectly delivering on its preset mandate References BARNETT, P., WOODGATE, J., JONES, S., & INGLIS, S. (1991). Stadium public address systems. Football Stadia Advisory Design Council. PETTO, A. J., & GODFREY, L. R. (2007). Scientists confront intelligent design and creationism. New York, W.W. Norton & Co. Read More