Children who say hand dryers ‘hurt my ears’ are correct: A real-world study examining the loudness of automated hand dryers in public places

Introduction Previous research has suggested that hand dryers may operate at dangerously loud levels for adults. No research has explored whether they operate at a safe level for children’s hearing. Children’s ears are more sensitive to damage from loud sounds than adult ears. Health Canada prohibits the sale of toys with peak loudness greater than 100 dB. This study tested installed dryers in public washrooms to see if they were safe for children’s hearing. Methods Forty-four hand dryers in public washrooms were each measured for peak sound levels in a standardized fashion, including at children’s ear canal heights. Each dryer was measured at 10 different combinations of heights and distances from the wall, and with and without hands in the air stream coming from the hand dryer, for a total of 20 measurements per dryer. Results Xlerator units performed the loudest, with all being louder than 100 dBA at all measurements whenever hands were in the airstream. Several Dyson Airblade models were also very loud, including the single loudest measurement of 121 dBA. While some other units operated at low sound levels, many units were louder at children’s ear heights than at adult ear heights. Discussion Many dryers operated much louder than their manufacturers claimed, usually greater than 100 dBA (the maximum allowable noise level for products/toys meant for children). Conclusion This study suggests that many hand dryers operate at levels far louder than their manufacturers claim and at levels that are clearly dangerous to children’s hearing.

Many public washrooms have hand dryers instead of paper towels. Informally, parents have said that their children refuse to go into particular washrooms because the dryers are too noisy, and children say they ‘hurt my ears’. Previous research has shown that hand dryers are much louder in real life than in sound testing laboratories (1).

The US National Institute for Occupational Safety and Health (NIOSH) has recommended that adults should not be exposed to more than 85 dBA within an 8-hour period, and ‘exposures at and above this level are hazardous’. (2) Children’s ears are more sensitive to noise and damage may happen quicker (3). More children lately are getting noise-induced hearing loss (4), and the more exposure children have to loud noises, the more likely they are to have hearing problems later in life (4). Children’s sense of hearing continues to develop during their first several years of life, and loud noise exposure in this period can damage their hearing development (5). The Environmental Protection Agency advises that noise greater than 85 dB is dangerous to children’s hearing, and all children require hearing protection at that level (6). Sudden exposure of children to noises greater than 100 dB can lead to learning disabilities, attention difficulties, and ruptured ear drums (7). The Canadian government has prohibited the sale of toys with peak loudness greater than 100 dBA due to the danger they pose to children’s hearing (8,9).

Two major manufacturers of high air flow hand dryers report their dryers operate at 70 to 80 dB (Xlerator dryers made by Excel Dryer Inc.) (10), and 81 to 85 dBA (Dyson Airblade dryer models made by Dyson) (11–14). Excel states the noise from Xlerators “can jump to over 90 dB when hands are perpendicular to the airflow and held extremely close to the air outlet.” (10) Excel provides a noise reduction nozzle for Xlerators as a ‘no-cost option’, which they say reduces the sound by 9 dB (10).

This study was designed to find out how loud hand dryers are in real-life scenarios at children’s and adult ear heights. A specific goal was to find out if any operated at higher than the 85 dB safety threshold and the 100 dBA maximum threshold for children’s toys.

The study was conducted in public washrooms with hand dryers in Alberta, Canada from December 2015 to February 2017. Locations that children might frequent were purposefully selected (schools, libraries, arenas, shopping malls, recreation facilities, science centre, restaurants etc.). When such locations had hand dryers, they were tested; on two occasions, hand dryers appeared to be malfunctioning and were not tested. Dryers in other convenient locations such as university buildings were measured to increase the sample size. For each washroom, the type of hand dryer and date of manufacture were recorded.

A decibel-meter (Extech Instruments, model 407730) was used to measure the peak loudness of hand dryers at two distances from the wall: 45 cm from the wall (the distance commonly used by manufacturers for testing) and at 30 cm, as many children’s ears are approximately this far from the wall when using a hand dryer. (Peak loudness is the approach required by Health Canada in testing toys for noise levels (9).) The meter used is reported to have accuracy within 2 dBA, has European CE certification (15), and has been used to validate the performance of mobile-device sound meter apps (16).

Each dryer was measured at five different heights, as described in Table 1.

Table 1. (1) The average ear canal height of 3-year-old children (83.5 cm)* (2) The author’s ear canal height at the start of the study (127 cm) (3) The average ear canal height of adult women (149 cm)* (4) The average ear canal height of adult men (161 cm)* (5) The height of the outlet jet of the hand dryer, as some children’s ears will be at this height. (1) The average ear canal height of 3-year-old children (83.5 cm)* (2) The author’s ear canal height at the start of the study (127 cm) (3) The average ear canal height of adult women (149 cm)* (4) The average ear canal height of adult men (161 cm)* (5) The height of the outlet jet of the hand dryer, as some children’s ears will be at this height. View Large

For each dryer, noise was measured with the machine running without hands (‘plain’) and with hands in the dryer air flow (‘hands’) for each combination of height and distance from the wall, yielding a total of 20 measurements for each machine. Adjusted decibels (dBA) were measured as they more accurately capture loudness as it relates to human ears (17), is commonly identified in industry brochures, and is the methodology required by Health Canada for testing toys (9). Adjusted decibels discount the loudness of sounds outside the normal range of human hearing; as a result, dBAs conservatively measure the sound level of a device.

Measurements were only taken when there was no background noise in the washroom (such as toilets flushing or people talking) and when there was no wind or moving air. Peak loudness (in dBA) was measured just after initiation of the dryer and by holding the decibel-meter horizontally at the correct height and distance from the wall. Measurements were taken over 12 seconds, or until there was no change in the peak measurement for 5 seconds, whichever was longer. (This exceeded the minimum recording duration in the methodology required by Health Canada for testing toys (9).) Several readings were taken in this manner for each measurement to ensure the readings were consistent. (The study’s author and assistants wore noise-cancelling headphones during the measurements as a safety precaution for their own hearing.)

Twenty measurements of loudness (dBA) were taken for 44 different hand dryers installed in public washrooms, for a total of 880 measurements. Xlerator and Dyson dryers were frequently installed, while only one model of each of the following was found in use: Blast, Model 0, Electric Aire, Lovair, Mitsibushi, One Comac, and Ouellet Galaxy 2. None of the Xlerator models had the manufacturer’s reduction nozzle installed.

In general, hand dryers were louder when hands were within the air flow, as compared to without hands in the air flow. Older-looking (and slower air-flow) dryers were usually quieter than newer dryers which appeared to have a high air flow. The noise results for the dryer models tested are shown in Table 2. (When multiple devices of the same model were tested, their measurements were averaged by the following methodology. The logarithmic value in dBA was divided by 10 and then 10-base anti-log was performed to arrive at its linear value. The linear sound level values for each of the same models for the same measurement were then averaged. A log 10 was performed for this value, which was then multiplied by 10 to get the mean dBA.) (18).

Table 2. View largeDownload slide Mean noise level results for hand dryers in dBA

All Xlerator models, the Blast, and the Dyson Airblade and Airblade V models were louder than 100 dBA when hands were in the air flow, for all measurements. The loudest reading (121.1 dBA) was with the Dyson Airblade V, when hands were in the air flow and loudness was measured 30 cm from the wall at the height where air exited the machine. One Dyson model, the Airblade dB, performed quieter than the other Dyson models, with only two mean readings greater than 100 dBA, but with a total of 12 readings greater than 85 dBA.

Some models were very quiet. The One/Comac model had all measurements less than 85 dBA. The Bobrick 750 and Ouellet Galaxy 2 both had only one measurement greater than 85 dBA and all less than 90 dBA. The Electric Aire and World Dryer RA-5 models both had two measurements greater than 85 dBA and all less than 90 dBA. The Nova 1 model had seven measurements greater than 85 dBA and all less than 90 dBA.

Protecting human hearing is important to prevent hearing disability and learning difficulties (7). It is particularly important to protect children from loud noises as their ears are more sensitive to damage from loud noises than adults (3). The louder a sound, the shorter exposure is needed for hearing damage to occur (3). As well, sudden loud noises (such as with a hand dryer) pose greater risk than gradually increasing noise because there is no time for the facial nerve to protect the ear by ‘dampening’ the ear ossicles (bones that transmit sound within the ear) (3). Loud noises cause a several hour reduction in hearing ability called noise-induced threshold shifts (NITS); with repeated NITS, hearing can be permanently decreased (3).

NIOSH has determined that there is no safe duration of unprotected exposure to sounds greater than 111 dBA (2). Given the greater sensitivity of children’s hearing to damage from noise (3), and due to children’s smaller and shorter ear canals, it has been suggested that children perceive noise at up to 20 dB louder than adults (19). This means that there is no safe duration of exposure for children to sounds greater than a level somewhere between 91 and 111 dBA. The exposure of children to sudden (brief) noises above 100 dB has been linked to learning difficulties and attention difficulties (7). 100 dBA has been selected by the Canadian government as the maximum allowable peak noise level for children’s toys (8,9); this suggests the same standard should apply to any products routinely used by children. Repeated and prolonged exposure to noise less than this level also poses a risk to children’s hearing (3).

As shown in a Dyson video (20) (manufacturer of the Airblade dryers), some manufacturers appear to measure the loudness of hand dryers in controlled conditions in the middle of a room with sound-absorbing walls, and at adult ear canal heights. Excel reports a methodology in which the dryer is mounted on a wall at the ‘standard mounting height for adults’, with measurements taken at 18 inches from the wall and 5 feet from the floor, with both no hands under the dryer and with hands in the air flow. The methodology used in this study was influenced by the Excel methodology, with the loudness of hand dryers being measured in real-life installed conditions, at the points in space where user’s ear canals would be for a variety of users including children, and in real-life usage. Positioning the decibel meter’s microphone where children’s ear canals are likely to be in relation to the noise-emitting device (as in this study) is the same approach as in the methodology required by Health Canada for testing toys (9).

In general, older-appearing hand dryers tested quieter than newer hand dryers. While drying times were not measured in this study, the older dryers appeared to be slower at drying hands. It seems that as hand dryers have become faster at drying hands, they have become louder.

All 14 Xlerator units tested were extremely loud, with all exceeding the Canadian legal limit of 100 dBA for peak noise levels for children’s toys (8,9) when hands are in the air flow, and all but one model exceeding this level at children’s ear heights when operated without hands in the air flow. The Xlerator readings were far above their stated operating loudness of 70 to 80 dB (10). This suggests that the testing methodology used by the Xlerator manufacturer may need to be reviewed. Xlerator acknowledges that their dryers can “jump to over 90 dB when hands are perpendicular to the airflow and held extremely close to the air outlet” (10). In this study, the hands were held at a normal user’s drying distance (not ‘extremely close’), yet all Xlerator dryers were louder than 100 dBA whenever hands were in the air flow. One of the reasons they are louder in real life might be due to increased echoes in public washrooms, which is also what Berkowitz thought was the cause of hand dryers being loud up to 10 feet away (1).

The Dyson Airblade and Airblade V models similarly exceeded 100 dBA when hands were in their air streams. These dryers exceeded their stated ‘rated operating noise power’ of 84 dBA (11) and 85 dBA (12), respectively. Only one Dyson Airblade Tap model was found installed; it also exceeded 100 dBA at all height and distance measurements when hands were in the air stream, except for one adult male height measurement. Its reported operating noise level is 85 dBA (14). These differences are likely explained by the differences between how Dyson measures their machines’ sound (in a controlled sound lab with sound-absorbing walls (20)), and how they were measured in this study (in real-world settings and at the heights of different users).

The Dyson Airblade dB (a new version designed to be quieter than their other models and marketed as operating at 81 dBA (13)), usually operated at less than 90 dBA during this study. However, two of the three Dyson Airblade dB units measured jumped to at least 105 dBA at the 3-year-old children’s ear height—four times the loudness claimed by the manufacturer (13) and a level dangerous to children’s hearing.

The Blast dryer was also found to operate above 100 dBA when hands were in its air stream; only one Blast dryer was found installed in a public washroom and tested in this study.

This study reveals that not all hand dryers are equal in their hearing safety. These results can be used to guide regulators, builders, and landlords in making decisions about which dryers to install in public facilities. This study also reveals a clear discrepancy between what two major companies claim about their dryers’ sound performance and the real-world operating sound levels of their hand dryers. Finally, this study shows the importance of measuring dryer loudness at the location of children’s ears as multiple dryers were much louder at children’s heights than at adult heights.

This study was limited in several ways. For many dryer models, only one device was found installed in public washrooms. If one of these performed loudly, it does not mean all machines of the same model would be equally loud. Other hand dryer models are available in Canada but were not found, meaning they were not tested. While the results of this study are concerning—that many hand dryers are operating at noise levels dangerous to children’s hearing—this is still only one study. Health Canada could ensure these hand dryers are tested again. If the results of this study are confirmed, Health Canada could explore regulations that require new and existing hand dryers to operate at noise levels that are safe for children’s hearing and be tested using a methodology that resembles real-world use.

This study builds on previous work by Berkowitz discussed earlier (1), by identifying how loud hand dryer sounds are at the heights and wall distances of children’s ears. This study confirms the findings of Berkowitz that suggest hand dryer sound levels should be tested in real-world scenarios.

Further work in this area could expand to increase the numbers of different dryer models tested, and increase the numbers of units of each model tested. Additionally, the effect of adding baffles or other devices to reduce the noise level of hand dryers could be examined, as a way to protect the hearing of users, particularly children.

In conclusion, when the loudness of hand dryers was measured at the height of children’s ears, they were usually louder than the measurements at adult heights. Older hand dryers were usually not as loud as newer types of hand dryers. Xlerator (Excel) and two models of Dyson Airblade hand dryers were far louder than what the companies claimed and always exceeded established Canadian maximum allowable noise levels for children’s toys. This study shows that children who have complained about loud hand dryers have been right all along about the dryers hurting their ears.

This study was originally presented at the Calgary Youth Science Fair.

Funding information: There are no funders to report for this submission.

Potential Conflicts of Interest: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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