air - powered hand dryers in public restrooms have become more common in recent years , replacing paper towels in many settings .
this change results in less trash , but the noise generated by hand dryers is often found to be noxious and extremely loud . in a large restroom , such as at an airport or a casino , where many hand dryers are often in operation at once , and the workers might clean one restroom for the majority of their workday , the noise generated can reach dangerous occupational levels . in this investigation
, the researchers measured the intensity of sound produced by hand dryers on campus at 2.5 ft , 5 ft , and 10 ft from the source and compared these measurements to manufacturers data and occupational safety agencies recommendations .
occupational noise is a known health hazard because it can lead to noise - induced hearing loss .
according to the occupational safety & health administration ( osha ) of the united states , workers should not be exposed to more than 90 dba in an 8-h shift .
the national institute for occupational safety and health ( niosh ) mandates that workers should not be exposed to more than 85 dba in an 8-h workday .
many countries around the world have a similar policy to that of niosh , based on the world health organization ( who ) recommendations .
however , subtle changes in speech perception have been reported in workers exposed to only 80 dba , even though they were within the normal limits on a pure - tone hearing test .
train operators were given a battery of auditory tests , and compared to a control group without noise exposure .
they scored significantly more poorly on a test of duration patterns , and on perception of sentences presented with 4-talker babble at a signal - to - noise ratio of -5db . in light of this
restroom patrons use the hand dryers at an arm 's length , obviously , which we estimated to be 2.5 ft .
however , daily experiences showed that the dryers were informally perceived as overly loud by patrons far across the room as well .
based on the inverse - square law , it would be predicted that the intensity at 5 ft would be 6 db less , and at 10 ft , 12 db less .
if the sound was attenuated in this way , it might reduce the risk to maintenance workers ; thus , the dryer output was measured at these three distances .
the patrons may find the dryers annoying , but for the workers , the hand dryers have the potential to be dangerous .
manufacturers of hand dryers provide specification sheets , installation manuals , and sell sheets for their products where one might expect to find clear information about the predicted sound intensity produced by their various models , as this might enable comparison shopping when planning a public washroom .
dyson publishes a sound power level of their dryers on the technical specification pages for each model .
their newest model is purported to produce 81 dba , but the model studied here is rated at 85 dba .
sound level measurements for the excel dryer 's xlerator were in a separate document , which states that the dryers operate at 78 - 80 dba , but as high as 90 dba if the hands are held in a particular way .
the specification sheets for world dryer 's airforce only stated that the dryer had a  low sound level .  upon writing to the company , it was intimated that airforce operates at 80 dba without hands and 88 dba with hands ( e - mail communication , eileen malloy , january 3 , 2014 )
. the reported duration of a drying cycle for the three above mentioned dryers were 10 - 15 s , 12 s , and 12 s , respectively .
the researchers measured the noise level in campus restrooms at a distance of 2.5 ft ( approximately at an arm 's length as one would use the dryer ) , 5 ft , and 10 ft ( space permitting ) .
measurements were taken with a digital sound level meter , model # 33 - 2055 from radioshack .
the researchers measured each hand dryer three times at each distance , taking the average reading for one drying cycle in each trial .
for each of the eight hand dryers , the mean of the three average sound level measurements was calculated at each distance from the source [ table 1 and figure 1 ] .
based on the inverse - square law , one would expect a 6 dba drop at each doubling of distance , however , this was not the case
. the mean intensity for all the readings at each distance was also calculated , and found to be 87 dba at 2.5 ft ( from the dryer ) , 84 dba at 5 ft away , and 82 dba at 10 ft away .
the most intense sound recorded across all the trials was 91 dba , and the least intense was 80 dba .
measurements of sound intensity in dba average sound intensity in dba for hand dryers in eight bathrooms .
markers are drawn at 80 dba and 85 dba , to reflect niosh / who recommendations and those of kumar et al .
measuring the sound output of restroom hand dryers confirmed what many have commented on anecdotally : these dryers are loud . on the whole
, the dryers studied in this investigation produced more intense sound than predicted by the manufacturers , and the reverberations produced in the bathrooms reinforced the intensity even at 10 ft from the source of the sound .
at all the distances measured , a full - day exposure at work could damage overall hearing and speech perception in particular .
people who work in maintenance positions , judged to be within compliance for noise exposure , may find themselves with an additional source of noise when bathrooms are installed with hand dryers rather than the earlier use of paper towels .
employers with hearing conservation programs should add these hand dryers to their list of possible harmful sources of noise .
multiple dryers running at once , an event that was not tested in this study , would result in an increased sound intensity , estimated to be 6 dba more for each doubling of the number of machines , adding to the burden on workers ears .
employers might consider deploying sound dosimeters to actually test the exposure of workers over the course of a workweek , to see if intervention is necessary in specific workplaces .
future studies should include a larger sample size of hand dryers , installed in various locations , to continue the comparison between the field data and the manufacturers reports .
additionally , it would be worthwhile to measure how long employees and restroom users are exposed to dryer noise , and at what intensities .
different hand postures while drying can also affect the sound level produced and could affect the noise exposure for nearby workers .
perhaps methods to reduce noise exposure from hand dryers are on the horizon ; however , many currently installed loud dryers are in service and are likely to remain so for years .
they are typically sold with a 5-year warranty , but can have a much longer service life . as our communities reduce the use of paper towels , a noble pursuit , they inadvertently increase the assaults on our ears .
 high airflow hand dryers are found in many public restrooms today . 
 these dryers offer quick and clean hand drying , and are seen as being an environment - friendly alternative to paper towels . 
 however , many new hand dryers are loud , exposing individuals using the facilities as well as those employees who clean the facilities to potentially dangerous noise . 
 prolonged exposure to high levels of occupational noise can cause damage to hair cells in the cochlea , resulting in varying degrees of noise - induced hearing loss . 
 this study examined the intensity ( in dba ) of the noise produced by the air dryers in campus restrooms . 
 hand dryer peak and average noise was measured with a sound level meter at 2.5 ft , 5 ft , and 10 ft from the dryer . 
 noise measurements did not decrease as predicted by the inverse - square law , probably because of the reverberative surfaces found in the restrooms . 
 the small sample of hand dryers tested was mostly found to be producing more noise than the manufacturer claimed they would ; indeed , none of the dryers would be safe for an 8-h workday exposure . 
 while hand dryers do reduce paper trash , they pose as a different sort of hazard to our environment and population . 
Introduction
Materials and Methods
Results
Discussion