THE SOUNDS OF SIRENS

The distinctive wail of a siren is a universal signal that demands attention. Sirens warn of danger, prompt action, or remind everyone that teatime is over. In an area in which machinery creates a loud ambient noise, a siren is especially vital. In fact, it is often the only way to communicate with the employees and visitors; whether it is to clear them from an area or to convey a standard message. KAMA Industries is a South African siren manufacturer that provides a range of warning devices to make your workplace safer and more efficient. And, as the largest manufacturer of sirens in the Southern Hemisphere, we supply custom-designed products globally.

 

What Are Frequencies and Decibels?

Sound frequency is the speed of the sound vibration. This periodic mechanical vibration (in the form of compression waves) determines the pitch of the sound and it is measured in Hertz (Hz). As the period (or speed) changes, so does the sound. The human ear is able to hear sound with a frequency as low as 20Hz and as high as 20 000Hz. Low-frequency sounds include rumbles and growls. High-frequency sounds are like sizzles and hisses. Speech ranges between about 100 and 8 000Hz

Decibels are the intensity or volume of the sound being produced. Normal speech between two people will be at around 50 or 60dB. Women can usually only reach around 75dB when shouting and men can reach about 100dB. An ambulance siren is about 120dB.

Decibels decrease dramatically over distance. Refer to the Decibels vs. Distance chart below to get a better idea of how distance affects the intensity or volume of the sound.

Decibels vs. Distance chart

Understanding sound frequency and volume, and how ambient noise and distance will influence these is essential to deciding on the best sirens for your specific application and purposes

 

Low-Frequency Sounds

Low-frequency sounds have longer wavelengths and fewer cycles per second, which means that they can travel further because they can diffract over obstacles (like machinery or hills) more easily. They sound like the bass that you hear from cars playing loud music in the traffic.

Ambient noises – like the hum of machines, the buzz created by conversation, and the roar of the ocean – are usually low-frequency sounds. So, although a siren that emits a low-frequency sound may be audible over longer distances, it may also be drowned out by ambient noise.

THE PRO: Low-frequency sounds carry over longer distances and can be heard from further away.

 

High-Frequency Sounds

High-frequency sounds have shorter wavelengths and more cycles per second. They therefore have a higher pitch; like the squeak you might hear from someone’s headphones. When it comes to sirens and their output, high-frequency systems tend to be more effective in noisy environments. Their high-pitched sounds may not cover as much distance, but they cut through the noise of chatter and machinery very effectively.

THE PRO: High-frequency sounds are able to cut through low-frequency interference and can be heard more easily in noisy areas or factories with an ambient hum.

Examples of industry noise levels in dB(A)

industry noise levels in dB

 

Examples of low-Frequency Sirens

Sirenco 15D siren

The Sirenco 15D is a fantastic example of a low-frequency product that has been designed and manufactured by KAMA Industries. This has an enclosed, all-weather motor that is designed for use outdoors. It works as an audible warning device in mines, oil rigs, refineries and industrial settings. The Sirenco 15D is used when there is a fire, an open-cast mining operation, or as blasting sirens. It produces an effective and powerful low dual-frequency sound that covers longer distances. It can be connected to an RF Transmitter so that the siren can be activated remotely.

Sirenco 15D Siren

Specifications

Sound output: 145dB at 1m

Sound frequency: 480/560Hz

Approximate range: 15km in still air on a flat area

Sirenco 3LF siren

This siren is durable, fit for any type of weather condition. It has been made out of the highest quality cast aluminium and the low-frequency output is extremely powerful. It is well suited for factories, refineries, industrial sites, quarries and construction sites; where there is a lot of ambient noise. It has thermal cut-off protection and can be used in underground and above-ground non-fiery mines.

Sirenco 3LF Siren

Specifications

Sound output: 125dB at 1m

Sound frequency: 560Hz

Approximate range: 3km in still air on a flat area

 

Example of a high-Frequency Sounder

E2S A121 Sounder

These sounders and combos are robust and well suited to general signalling (for fires, security or process control). The entire E2S range has been designed to perform for as long as is necessary at their maximum capacity. There is a volume control for those that need to be able to adjust how loud the output is.

E2s A121 Sounder

Specifications

Sound output: 126dB at 1m

Sound frequency: 340/2 400Hz (depending on the volume you choose)

Approximate range: 1km in still air on a flat area

 

KAMA Industries Siren Manufacturer

At KAMA, we design and manufacture a wide range of sirens and sounders. After a thorough analysis of your needs and requirements, we will implement the most effective solution for you, your employees, and your business. Call us today on 011 472 3980 or e-mail us on info@kama.co.za to arrange for a meeting or request a quotation.