FAQs Horns and Backup Alarms

A warehouse is a very noisy and busy place. Workers are walking from between shelves and boxes and may not be aware of a forklift that is backing up into the route in which he is traversing. Under circumstances like this a loud, audible alarm or horn can alert a pedestrian of a possible encounter. Of course, it is also the responsibility of the forklift operator to drive responsibly.

Forklift Accessories stocks various backup alarms and other types of alarm systems to assure safe warehouse operations.

For those of you who are considering the purchase of an alarm what follows are answers to frequently asked questions concerning the use and operation of an audible alarm.

Q: What is an electronic audible alarm?
A: There are actually two types of audible alarms –- an electronic alarm and an electro-mechanical alarm. An electronic audible alarm uses electronics to blast out a loud audible warning sound. An electro-mechanical alarm uses a mechanical method to blast out the sound. Electro-mechanical alarms include school bells and car horns. A forklift backup alarm makes a noise using electronic means.

Q: What else are audible alarms called?
A: There are a wide variety of names including buzzers, beepers, audible signals, piezo, sounders, alerts, audio alarms, indicators, transducers and various combinations of these terms including audio alert, piezo indicators, and more.

Q: How do electronic audible alarms work?
A: Electronic audible alarms feature electronic components that convert input voltage into an oscillating signal that drives a metal sounder diaphragm. The diaphragm physically flexes up and down to produce air pressure waves that the human ear interprets as sound.

Q: How is sound level measured?
A: Sound level is measured in decibels (dB). The dB scale is an arbitrary scale that defines the loudness of the sound being measured. The scale runs from 0 dB, or the threshold of hearing, to 130 dB, which is the threshold of pain.

Q: How loud does an audible alarm need to be?
A: The level of sound coming from an audible alarm should be at least 10 dB louder than the ambient background noise so that it can be easily heard. You can use a sound level meter to measure the actual ambient noise level.

Q: When is sound level twice as loud as another?
A: Sound level must increase by 10 dB to consider being twice the level of the previous sound. That sound level appears twice as loud to the human ear.

Q: Does distance have any influence on sound level?
A: Sound level falls off over distance. Experts in this field say that every time the distance doubles, the sound level drops off by 6 dB. For example, if a forklift backup alarm bursts out a sound that is 60 dB at 2-feet, then when the sound reaches 4-feet, it will be 54 dB. By the time it reaches 8-feet, it will be 48 dB and so on.

Q: How do I compare alarms at various distances?
A: There is no one standard distance for identifying sound level for an audible alarm. You will have to test the dB of the alarm at various distances including 2-feet (60 cm), 1-foot (30 cm) 4-inches (10 cm), etc.

So, if you want to compare an alarm that blasts out a 100 dB sound at 10 cm with another alarm that blasts out a sound that is 88 dB at 2-feet, you have to choose one distance to compare the two. According to a distance conversion spreadsheet, an alarm that sounds at 88 dB at 2-feet equates to an alarm that sounds at 103 dB at 10 cm. So an alarm identified as an 88 dB model at 2-feet is actually louder than the 100 dB at 10 cm.

Q: How sensitive is the human ear to sound level changes?
A: Most people can discern a sound level change when the sound increases or decreases by 3 dB.

Q: What does A-Weighting (dBa) mean?
A: A-weighting means that the sound level was measured on an A-Weighting scale. This scale was created because the human ear is not an ideal microphone. The A-Weighting scale puts the different frequencies that an audible alarm produces on an even basis. This permits you to compare different audible alarms on an apple-to-apple basis.

Q: What is the difference between “UL Listed” and “UL Recognized”?
A: “UL Recognized” means that a component has met the requirements of the Underwriter’s Laboratory for that type of component while equipment is “UL Listed.” So “UL Recognized” components are used in “UL Listed” equipment.

(Source: Mallory Sonalert Products, Inc.’s FAQ Application Guide)