A police siren is a loud electronics device that produces sound similar to police siren. Police siren is used to get other road users or drivers on the road out of their way.
Electronic sirens incorporate circuits such as oscillators, modulators, and amplifiers to synthesize a selected siren tone (wail, yelp, pierce/priority/phaser, hi-lo, scan, air horn, manual, and a few more) which is played through external speakers. It is not unusual, especially in the case of modern fire engines, to see an emergency vehicle equipped with both types of sirens. Often, police sirens also use the interval of a tri-tone to help draw attention.
This police siren simulated electronic project uses two 555 timers IC to generate a sound similar to the police siren. A single 556 timer IC which consists of two 555 timers can also be used. In this circuit, both of the timers are configured as astable circuit.
The first timer is configured as a square wave close to 1 Hz astable oscillator. The output of this timer is used to feed the control voltage of the second timer where it is subjected to frequency modulation. This frequency modulation will generate a tone similar to the siren used by the police.
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Nowadays, there are a lot of emergency lights systems being used all over the world, and we can not discuss all in this work. Police siren has been around for a while and, although the most common type today is the so-called lightbar, there was a time when the whole system was a lot simpler. In 1940, police departments used just a single beacon to attract everyone's attention and let them know that an official vehicle is approaching. Just like it happens today, when the siren was turned on, the other drivers (if any, given the traffic values at that time) were requested to clear the road and thus allow the police to pass safely.
Using this kind of technology had multiple advantages and the ace up its sleeve was definitely the cost. Purchasing a single beacon was of course a lot more affordable than investing in more complex solutions. Plus, since cars weren't quite that fast at that time, the air resistance such a beacon had to face was pretty low, which means it could serve its purpose very well.
But time passed by and law enforcement agencies looked for more advanced and, extremely importantly, more efficient technologies. The single beacon we were talking about turned into a magnetic-mount system that allowed on-the-go use and which, in its turn, got replaced by full-sized lightbars with multiple sound.
What you're seeing today is what could be called the modern light bar which is, in essence, a contemporary interpretation of the traditional light bar introduced in early 1990s. Obviously, the police siren sound may vary by country and the law enforcement organization that owns the vehicles.
1.2 OBJECTIVE OF THE STUDY
The objective of this study is to design an electronic device that produces sound similar to police siren.
1.3 SIGNIFICANCS OF THE STUDY
Police sirens are a necessity when officers are called to respond to a crime, clearing road traffic to allow a quicker response, the sirens serve as a calling card to the criminal and the victim that the police are on the way. sirens are to alert people that an emergency vehicle is approaching so that they can get out of its way. As such, the sirens are designed to catch drivers and pedestrians attention
1.4 THE EFFECTS OF POLICE SIRENS
Aside from clearing road traffic to allow a quicker response Sirens have ulterior effects, from societal to health issues.
- The average person has 30,000 hair cells the transmit sound waves into nerve impulses. Loud noise destroys them, thus affecting your hearing. Long term or close, sudden exposure to the average police siren, at 123 decibels, can affect hearing and even cause hearing loss.
- The World Health Organization said in 2008 that sudden noise from police sirens not only increases noise pollution, but also impacts a person's health, raising their heart rate and blood pressure and posing a serious health issue.
- The constant sound of police sirens can negatively affect an entire community, adding to a perception that the community is a "high crime" area or one where there is "increased danger" for residents.
- Accidents, sometimes fatal, do occur when police cars race to a crime scene with their sirens wailing. Once a driver hears the siren, his first instinct is to turn to the side of the road. But drivers may hear the siren and not see the police car, and their efforts to locate the police takes their eyes off the road, and into danger.
- Police sirens wailing throughout the night, particularly in high crime urban areas, interfere with sleep, which produces stress and anxiety. Police in many cities, such as Los Angeles, must follow strict guidelines when using their sirens when called to a crime.
1.5 SCOPE OF THE PROJECT
This police siren simulated electronic project uses two 555 timers IC to generate a sound similar to the police siren. A single 556 timer IC which consists of two 555 timers can also be used. In this circuit, both of the timers are configured as astable circuit.
The first timer is configured as a square wave close to 1 Hz astable oscillator. The output of this timer is used to feed the control voltage of the second timer where it is subjected to frequency modulation. This frequency modulation will generate a tone similar to the siren used by the police.
1.6 PROJECT WORK ORGANISATION
The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:
Chapter one of this work is on the introduction to a police siren. In this chapter, the background, significance, objective limitation and problem of police siren were discussed.
Chapter two is on literature review of a police siren. In this chapter, all the literature pertaining to this work was reviewed.
Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.
Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.
Chapter five is on conclusion, recommendation and references.
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