Choosing the Right Audible and Visual Signaling Devices for Different Applications
The type and intensity of sounders or beacons used in a particular area depend on the specific application. For example, sounders used in the food industry may not be suitable for industrial areas, and those used in heavy industrial manufacturing may not be appropriate for school environments.
- Industrial, Mining, and Manufacturing Applications This category includes factory premises, as well as equipment and facilities used in factories such as cranes, handling vehicles, generating sets, and control panels. It also encompasses hazardous locations like coal mines and the petrochemical industry.
- Building: Commercial and Public Applications Hospitals, schools, offices, building sites, houses, military sites, and airports fall under this category. Please note that due to continuous product research and development, some products may vary from the specifications in this catalogue.
- Priority and Public Service Vehicles This category includes police vehicles, fire department vehicles, and ambulances.
- Marine Applications Dock and ship installations, as well as other hazardous sites such as oil terminals, are covered under this category.
Frequency refers to the number of vibrations per second and is used to identify the note of a sound. It can be measured using a frequency meter. In cases where a frequency meter is not available, identifying the ambient noise frequency in the environment can suffice. For example, a machine shop with a grinder will have a high-frequency noise, while a forge with a drop hammer will have a low-frequency noise.
The time cycle over which an alarm is required to operate must be taken into account when selecting a signalling device. It is important to choose a signal with an adequate time rate. Note that sounders used as evacuation alarms are typically required to be continuously rated. Some products on the market have time ratings of one minute or more, but these may not be accepted by Fire Authorities. Contractors should be mindful of this when modifying or inspecting existing installations.
Required Noise Level
Once the ambient or background noise and frequency level have been established, the sound pressure level needed for the sound to be heard over the desired distance must be defined. Tests show that the ear can distinguish a warning signal that is ten decibels below the ambient noise level, provided there is an adequate frequency differential.
It is important to consider noise attenuation, which refers to the reduction in sound as the distance from the signal doubles. As a rule of thumb, sound is absorbed and reduced at a rate of 6 decibels. In challenging operating conditions, such as high winds or solid objects in the noise path, an attenuation of 8 to 10 decibels should be allowed for to avoid blind spots or inadequate coverage. Additionally, it is crucial to ensure that the same or similar sound is not used in adjacent systems for other applications before finalising the choice of signal. For outdoor installations exposed to exterior elements, a weatherproof version must be selected. Similarly, indoor situations that require weatherproof enclosures should also be considered. Explosion or flameproof signal devices are essential when the sounder is located in an environment with explosive or fire-hazard conditions.