Emergency Warning Sirens

Tactical Tooling has successfully developed, amongst other products, a new Warning Siren.

Independent testing has shown SIGNIFICANT GAINS BOTH IN NOISE LEVELS AND DISTANCE OF TRAVEL of sound waves (up to 4 times that of similar sirens on the market). The new design also offers significant improvements in coastal environments where the terrain is often hilly and in situations where PENETRATION OF NOISE INTO RESIDENTIAL HOUSING is required.

Based on tried and tested technology, but with significant advances in original design, we have developed a more COST EFFECTIVEsolution to emergency response.

When it comes to warning system the distance the sound travels, the acoustic colour, penetration and noticeability of the signal, are all factors in combination, to enhance its usefulness and coverage.

Efficiency
We have the BEST LONG-RANGE AND ACOUSTIC-QUALITY SIRENS AND BOOSTER KITS ON THE MARKET. This means FEWER SIRENS ARE REQUIRED, and therefore a much more cost efficient siren system for any location. We have the expertise and flexibility to produce a warning system to meet specific needs.

Siren1

Emergency Notification Systems
Several events over recent years have raised awareness of the importance of effective mass emergency notification systems (MEN’s). These systems were developed to deliver critical warning during life-threatening situations. Global events and subsequent studies have shown that simple fixed, noise-based systems are the most effective in attracting attention, and therefore action, from the vast majority of the population.

The sirens are easily REMOTE CONTROLLED by radio telemetry, via existing SCADA systems.

MAINTENANCE REQUIREMENT IS MINIMAL – periodic wash-downs to remove salt spray. Horns are 3mm marine grade aluminum, and all fastenings are 316 grade stainless steel.

Technical Points
A weakness with earlier Carter type sirens was their high acoustic cavity impedance (high pressure, low displacement), not being correctly matched to the very low atmospheric acoustic impedance (low pressure, high displacement) resulting in power being reflected back into the siren and lost as heat.

We have overcome that deficiency by the careful design of impedance matching transformer horns of critical curvature and dimension, to launch long wavelengths that will reflect off a variety of surfaces, thus making the siren more noticeable at very long distances.

The design includes rotating reflector cones that increase pressure gradient along the length of the quarter-wave transformer horn, to enhance pressure maxima at the throat and minima at the mouth. The result is significant, with a measured gain of 13dB (4.47 times the distance at which the siren can be recognised).

Unlike electronic hooters, the Tactool siren does NOT generate a conventional tone or continuous wave. It generates individual shock waves in the form of discrete triangular pulses at the rate of 500 shocks per second giving the signal a unique and intimidating sound that is instantly recognised at long distance, even amongst local noise.

Siren2

The enduring nature of the pulse shape in free air enables the signal to be easily reflected off a variety of surfaces including bush-covered hills, so the siren gets heard over a wider area than other types of siren. This is primarily because the machine has a rotating valve system to produce a supersonic shockwave by rapid air movement, so is not inhibited by the acceleration forces that are present with vibrating membranes as is the case with electronic sirens where vibrating diaphragms are used to produce sinusoidal sound waves.

The Tactool siren is not always adversely affected by wind. There are times when wind will alternately enhance the chances of the siren being heard, due to the shape of the pulse allowing it to more readily reflect off wind shears, and partly due to the huge number of reflections present anyway.

During WW2, lower power versions of the Tactool siren were wound up and down to give the alert, and run at constant speed to give the all clear, in a simple unambiguous code that is still internationally accepted.

Maintenance free life is decades – there is only one moving part that rotates on sealed bearings, with some 60 year old war sirens still in service at fire and forestry stations, including in marine environments.

Specifications for TACTOOL Model SW-MkII long range low maintenance siren.

Power output: 150dBA on-axis
Average overall spatial power : 145dBA.
Sound pressure level at 1 metre: 142dBA.
Power difference between full speed and one-third of full speed: 4.1dBA in all directions.
Fundamental frequencies: 500Hz and 600Hz at full speed of 2850rpm.
Gain of booster kit over an average Carter type siren: 13dB. Equates to 4.47 times theoretical distance multiplication (20 times power output)
Radiated waveform: triangular shock wave (N-wave) at 500 and 600 PPS respectively, at full speed.
Horn curvature: Tractrix.
Horn design cutoff frequency: 200Hz
Horn diameter: 600mm at mouth.
Horn length: 460mm (>λ/4 at 200Hz)
Siren length: 1500mm
Weight: 70kg.
Motive power: 400 volt 3-phase Delta, 5000VA.
Normal remote control mechanism: SCADA.
Alert signal: 15 second cycling between one third speed and full speed, with 5 second pause at full speed. (4.1dBA variation)
All clear signal: 30 second pause after alert signal, followed by 30 seconds constant run at full speed.
Reflector cone and horn materials: 3.0mm marine grade aluminium.
Fastenings and fixtures: 316 stainless steel.
Country of origin: All siren components are NZ built.

Calibration
Measurements were conducted by Marshall Day Acoustics, Wellington. Author of report: Dr Con Wassillieff. Sept 2012.