How the human ear works5 sound levels in decibelHow to prevent damage to hearingConsequences of damage to hearing8 best online hearing testsHumans can hear sounds between 0 and 140 decibels.  0 decibel does not mean that there is no sound, merely that we cannot hear it. 0 decibel is the so-called hearing threshold for the human ear.While we can hear more than 140 decibels, it is too painful for our ears and if you expose yourself to such a loud noise you are at extremely high risk of permanent damage to your hearing.  The table blow shows how loud sound is.Decibels metreAccording to United Kingdom legislation you are obliged to wear hearing protection if you work in an environment with 80 decibels of sound or higher on a daily basis. For fun, check out the folloing  decibel metre . Below the table is a video in which the volume within various genres (rock, hip-hop, dance, etc.) is shown.Example of decibelsDECIBELSOUNDEXAMPLE10Almost inaudibleA leaf falling20AudibleRustles of autumnal leaves30Very quietWhispering40Living room, quiet classroom50Limited soundRefrigerator working, car driving past55Percolating coffee-maker60AudibleSound of human voice, machinery70IrritatingTelevision set on loud, vacuum cleaner, several people on the telephone75Constant soundBusy restaurant around lunchtime80UnpleasantAlarm clock, freight traffic, doorbell85LoudSawing, mixer90Extremely unpleasantTruck close by, screaming, yelling, shouting95NoisyDrill, violin100Extremely unpleasantMachine in a factory, compressor, fighter jet at 300 m105Even louderHelicopter close by

, large drum110Extremely loudRock concert, chainsaw120Human voice at its loudest, police siren130Thunder140Pain thresholdFirst Monday of the month siren from close by150Permanent damage to hearingFireworks160Shooting with pistol or rifle170Avalanche firework180Rocket launch platform194Saturn rocket Please Donate and Help Us Help Others Harry the Hair Cell: Kids Need to Protect Their Hearing How Loud Is It? The best way to protect against hearing loss in the future is to protect your hearing today and every day.  A decibel level of 85 warrants consideration for ear protection. Children's hearing is more sensitive because the ear canal is smaller and sounds become louder as they develop in a smaller space. That can translate into as much as a 20 dB difference between an adult's ears and a child's ears which can cause a child's hearing to be damaged more easily. Ear plugs are especially useful to people exposed to excessively noisy devices or environments (85 decibels or more).

Listening to a portable MP3 music player too loudly or for too long could permanently damage your hearing, (American Academy of Audiologists). Being at close range to a single extremely loud sound such as a shotgun blast (about 145-165 decibels dB) can cause permanent damage to your hearing, but so can constant exposure to the more moderate levels of noise produced by music players. At peak volume, a music player can reach 110 to 120 dB. 91-96 dBA or more up to 125 dBA 90 dBA and upCarpet Cleaner Rental Gilbert Az up to 117 dBAGreat Dane Puppies For Sale In Jacksonville Fl 100 dBA or moreMoving Companies In New Liskeard up to 154 dBA in the car up to 116 dBA Leaves rustling in a breeze

Whisper at 5 feet Decibels (dB) are a measurement of sound intensity over the standard threshold of hearing. dBA is sound intensity with an "A" contour filter. The filter adjusts the measurement to account for the way in which the ear responds to different frequencies of sound. Learn how sound travels through the ear» Hearing Loss and Causes Noise Chart: Everyday Sounds Can Cause Hearing Loss Proper use and fitting of hearing protection is essential to safeguard your hearing. Instructions on how to properly use hearing protection » Exposure to loud noise will inevitably cause hearing loss over time. Loud noise damages or destroys the nerves/hair cells in the inner ear. Our ears can recover from short exposure to loud noise, but over time nerve damage will occur. The longer and louder the noise, the greater chance permanent damage will occur. Hearing loss from noise exposure is usually not noticed because it is so gradual. Usually a person loses the ability to hear higher pitches first.

Often the first noticeable effect is difficulty in hearing speech.Noise has always been and will continue to be a subject of discussion between the gearbox and motor manufacturers with their respective customer base. By its very nature it remains a controversial and subjectiveThe term “it’s too loud or it’s making noise” is often used to relay complaints from the end user back to the manufacturer. In this article, the goal is to provide some basic understanding of the dynamics involved and try to give some points of reference to help explain the mysteries of noise related issues within the power Fundamentals of noise and how it’s The terms “Sound Power and Sound Pressure” are used to define the category of theThe most commonly used is the “Sound Pressure or Sound Level” which determines a noise measurement taken at a known distance from the source. Typical distances are measured (in feet) away from the

source (i.e. 1 foot, 3 feet or 5 five feet, as examples). A decibel meter is used to collect readings from theThe decibel meter or (dB meter) can be a simple hand held device typically used in an open shop environment or an expensive sophisticated instrument set up in laboratory conditions. Sound Power is measured exactly at the source using the decibel meter and without any noticeableBoth terms (power and pressure/level) will be measured on the dBA scale and reported as such. The decibel meter approach will only measure overallIn other words “how loud is the machine element” and expressed numerically, (as an example;This numerical value will help take some of the subjectivity out by giving a value that all parties involved can relate to. While we now have a numerical value to compare against and we can all agree with, that’sThe dBA scale is a composite value without consideration for frequency and amplitude, it’ just

an “unfiltered” noise level for volume only. For general comparisons about noise related issues please refer to the following. are based on a distance of 6 feet (industry standard): • 30dBA is a whisper • 45 dBA is rustling of leaves, background music • 52 dBA is typical desktop computer • 60 dBA is normal conversation • 68-73 dBA is typical Boston Gear WGSR • 75 dBA is average radio, vacuum cleaner • 80 dBA is busy office • 82 dBA is inside coach section of typical passenger jet • 85 dBA steady sound levels for a working shift of 8 hours of is the maximum generally permitted as per the 1983 OSHA Published Standards. • 100 dBA tractor or power saw • 120 dBA is chain saw, jackhammer or snowmobile • 135 dBA is jet taking off, rock concert • 140 dBA is threshold of pain, gunshot or siren Above information is referenced in the Machinery’s Handbook-25th Edition page 1238

As mentioned previously, the above referenced are just noise levels or volume. missing are the characteristics of noise. are expressed in terms such as frequency and amplitude. It should be worth noting that the equipment required to record frequency and amplitude is typically expensive and tested under laboratory conditions. bore you with the science behind frequency and amplitude, they do play an important role in mathematically describing the type of noise thus leading to very good problem solving In short, the take away on frequency and amplitude could be described by the following example: We have a customer who is complaining that his system is too noisy. The decibel reading measuredIn relative terms, this is a quiet system but the customer is still saying it too noisy. an example only, by using specialized sophisticated equipment to determine the frequency and amplitude, we discover that the frequency could be in the 3000-4000

The human ear is most sensitive to the frequencies in this range. At low sound levels, the human ear is most sensitive to high pitched tones thanAt very high sound levels the human ear is virtually equally sensitive for all tones. volume of the noise is not loud by measurable terms it’s the frequency of the noise level which is the issue. Knowing the frequency and amplitude is the key to problemThis can direct the manufactures of equipment to focus on certain areas of noise generation. frequency is determined (expressed in numerical values usually between 0-20000 Hz) then “root cause analysis” can direct us to certain elements. Examples of gearbox noise generators could be gear tip relief, lead and profile error, pitch error, burrs, nicks, bearing noise, fan noise, motor noise, just to name a few. Examples of motor noise could be windings, bearings, fans, motor misalignment, and loose bolts at Examples of systematic conveyor noise

could be structural vibration, loose connection points, bearings, rollers and overlapping natural frequencies of different thickness of steel beams and plates. All of these mentioned have specific frequency characteristics in the hertz range. Practical Use of Decibel Meters: Noise levels produced by a single machine in a relatively quiet environment (no background noise) can be recorded via the hand held decibel meter. is a straight forward measurement and value. The real question that comes into play is when you have multiple pieces of equipment running, how do you determine which is producing the loudest noise or if other background noise is present? So if we don’t have the specialized equipment available to evaluate the noise condition, how will taking a decibel reading help you in your initial By using the hand held decibel meter you can rule out surrounding noise from other pieces of equipment if you apply the following logarithm.

scales are used to define normally large values into a smaller scale, thus preventing huge long numbers. For every 3 dB increase in sound level, this doubles the perceived sound for At the machine of interest, measure the total noise (t) and record the value. simply hold the hand held decibel meter in the air at arms length in front of you and in the general area of concern. This value will consider the total noise around the machine and any background Turn off the suspect machine and repeat the measurement procedure for background Plug in the values for (t) and (b) into the formula and solve for M (machine A speed reducer assembly complete with motor has been identified as noisy. It’s attached to a conveyor line but it is really hard to determine exactly where the noise is coming from. Is it the gearbox? Is it the motor? Is it the conveyor? Using the 3 step method above will help determine where the noise could possibly come from.

Step 1 would record the total noise of the system a (t=75) Step 2 would disconnect the chain sprocket from the conveyor and record the Step 3 would be: M = 10 log [10(75/10) – 10(70/10)] (Would be the noise of the gearbox & motor without conveyor background To take it one step further you could now measure the gearbox with and without the motor connected. Step 1 would record the total noise of the gearbox and motor running without Step 2 would disconnect the motor from gearbox and run motor (b=73) M = 10 log [10(71/10) – 10(73/10)] (Would be the noise of the gearbox without motor background noise). What we have just determined with this example, the motor is louder than the gearbox. case, we could say with confidence that we have localized the noise generator and have a decibel value associated Since both pieces of equipment (motor and gearbox) were close together in decibel readings, it would have been difficult to distinguish by the ear