Audible signals in Security Systems

 

 

Audible signals warn, protect and guide us in the modern world. They indicate emergencies, malfunctions or dangerous situations and demand direct action. Think at the buzzer of an egg timer or the sirens for public danger.

 

Decibel (Loudness) Comparison Chart

Here are some interesting numbers, collected from a variety of sources that help one to understand the volume levels of various sources and how they can affect our hearing.

Environmental Noise
Weakest sound heard	0dB
Whisper Quiet Library	30dB
Normal conversation (3-5')	60-70dB
Telephone dial tone	80dB
City Traffic (inside car)	85dB
Train whistle at 500', Truck Traffic	90dB
Subway train at 200'	95dB
Level at which sustained exposure may result in hearing loss	90 - 95dB
Power mower at 3'	107dB
Snowmobile, Motorcycle	100dB
Power saw at 3'	110dB
Sandblasting, Loud Rock Concert	115dB
Pain begins	125dB
Pneumatic riveter at 4'	125dB
Even short term exposure can cause permanent damage - Loudest recommended exposure WITH hearing protection	140dB
Jet engine at 100', Gun Blast	140dB
Death of hearing tissue	180dB
Loudest sound possible	194dB

Environmental factors

In addition to the sound output level, the tone frequency and the distance to the signal device, environmental factors as wind, humidity, rain have an effect on audibility. A very important factor is the ambient noise level. In industrial environments in particular, the ambient noise level produced by machines is often very high. Accordingly, the signal devices must produce a sufficiently high sound output in order to be heard.

 

 

 

and last but not least