DIRECTIONAL SIRENS LTD
  • Home
  • About
  • Technical Information
  • Research
  • Jez Brandon
  • Health and Safety
  • Patent
  • Specifications
  • Standards
  • Contact

DIRECTIONAL SIRENS LTD
MANUFACTURER OF DIRECTIONAL emergency vehicle SIRENS


HEALTH AND SAFETY

HEARING DAMAGE  

•  Research into siren induced hearing damage to emergency services personnel confirms that this is a significant problem


•  Undoubtedly it was not the intention of the manufacturers to cause hearing problems and they designed their sirens with the skills and knowledge available at the time. Over an extended period the problem was identified and reasons for the damage isolated using measuring devices and computational power not previously available

•  In the United States over 200 fire departments are engaged in ongoing litigation against siren manufacturers

•  Government research as far back as June 1979 demonstrated the problem. click here for published research 
There is a solution - the Quadrasonic™ Siren System - which is being launched soon


VEHICLE CRASHES

The Department for Communities and Local Government statistics for 2012 - 13 registered 3,325 accidents
involving Fire and Rescue Service vehicles.  All Emergency Services suffer significant numbers of
vehicle accidents - many involving serious injury or fatalities to personnel and the public

•  Many serious crashes occur at crossroads and it is believed that directional sirens will significantly reduce these accidents

CAUSES of SIREN INDUCED HEARING DAMAGE


Picture




Research indicates that electronic yelp sirens can cause hearing problems in personnel. If we look at the graphs of the sirens we can see that in the initial period of each cycle of sound there is a very steep rise time followed by rapid fall times. The wail siren takes around 1.92 seconds to emit 75% of its peak volume (amplitude) in 30% of its total cycle time. Although its initial rise time is steep, it is spread over a long time period and is unlikely to cause hearing damage. 

However, a yelp siren  reaches 75% of its peak frequency in around 0.08 seconds and repeats it up to 250 times a minute. 

When our ears hear loud noises the ocular muscles tighten to avoid damage to the eardrum. When sounds are increasing and decreasing in intensity very quickly these muscles become overstretched and in time can lose their elasticity, leading to permanent hearing problems. The fine hairs in the cochlea of the inner ear, known as stereocilia, bend in response to sounds and generate electrical signals which the brain interprets as sound. Overstimulation by high frequencies can damage the stereocilia causing permanent hearing loss.

Unfortunately, damage to hearing is cumulative and adds up over time. Hearing loss is usually permanent.
Picture
In contrast to electronic sirens the Quadrasonic™ sirens emit sinusoidal soundwaves which have gentler rise and fall times allowing the eardrum muscles have more time to adapt to the increase in volume levels. The sinusoidal sound waves are less likely to cause hearing damage. The stereocilia are activated at a slower rate and are less stressed by the type of sound wave used in Quadrasonic Siren Systems.

"Occupational exposure to noise can increase the risk of temporary or permanent hearing loss"
Picture

In a recent Appeal Court Case the expert witness stated  " Firefighters were routinely exposed to 109.8 dB, 
an exposure range well above the permissible dose of acceptable noise exposure " 
The maximum recommended exposure at that level is a total of less than 2 minutes
Journey times to emergencies are usually between 7 and 12  minutes - several times a day
The firefighters won the case and were awarded compensation
 Table 9 - NIOSH Maximum Recommended Exposure Levels to Siren Noise
Picture

CASE STUDY

" One of the most prevalent occupational health problems is the control or moderation of high sound levels in the drivers seat of emergency vehicles"
Picture
click page to view document

Picture
Picture
Picture


FITTING QUADRASONIC SIRENS WILL REDUCE THE INCIDENCE OF HEARING DAMAGE AMONG EMERGENCY SERVICE PERSONNEL
​

DO EMERGENCY SERVICE PERSONNEL DESERVE TO HAVE THEIR WORKING CONDITIONS IMPROVED ?


jez.brandon@directionalsirens.com
www.directionalsirens.com
Registered office:
DIRECTIONAL SIRENS Ltd 
21 Wyndcote Rd
Merseyside
L18 2EB


phone   +44 (0)151 234 9887        
mobile  +44 (0)796 426 9350