A Guide to Hand Dryer Noise

Hand dryer noise is an important aspect for many people when deciding which hand dryer to purchase.  A general rule of thumb: the faster the hand dryer, the louder it is.  This is a cruel trade-off to getting a better, faster, more energy efficient hand dryer.  For many people, the noise does not bother them and indeed in a sports setting and many bars and restaurants, restroom noise does not matter.   (Many people love the Xlerator because "it's like a jet taking off," and it is a very effective hand dryer.)   For others, if the restroom is adjacent to a classroom or office, for example, the noise level is a major factor.

Below is a reprinting of a recent INDEPENDENT research paper published by the Acoustical Society of America. Hand Dryer Noise Report   This is the first time we can get an unbiased opinion regarding noise levels spanning across hand dryer manufacturers.

First our summary, and then the paper itself:

If hand dryer noise level is a major concern, go with the World Dryer Model A hand dryer.  This is one of the most durable hand dryers in the industry.  While not a "high speed" hand dryer, it is a good, solid hand dryer with about a 25 - 30 second dry time.  And it is pretty quiet. If you want almost no noise, then go with the Electric-Aire LE-1 or the Fast Dry HK-1800PA hand dryer.  The downside?  These dryers are very slow, with about a 45 second dry time. They are also not very durable (the fast dry has a plastic cover, the LE has a better aluminum cover.)   On the other hand, they are also very inexpensive hand dryers.

If noise is not concern, go with one of the high speed hand dryers.  Your customers will love them, and they are also extremely energy efficient, so they can help with LEED-type qualifications and they are inexpensive to operate.  The fastest two hand dryers, in our opinion, are the Dyson AirBlade and the Excel Dryer Xlerator.  Keep the Dyson clean, it will stay more efficient.  The World Dryer Airforce and AirMax are other great high speed-dryers - fast, but not as fast as the Xlerator and Dyson. The Airforce is a great price for a high-speed dryer.  The AirMax with the cast iron cover is probably is the most durable high speed dryer.

The following chart compares standard models (all with motion detector sensors) for these hand dryers.  The decibel ratings for the Dyson, Xlerator, and Model A are from the Acoustical Society of America report.  The others are provided by the hand dryer manufacturers.  Dry times are our own estimates and, as you can understand, they are subjective and subject to dispute.  Hand dryer manufacturers use their own techniques for measuring both dry time and noise levels.  So their data may be more accurate than our own estimates which are not scientific.

Hand Dryer	Model #	Dry Time (sec)	Cost ($)	Decibels
Dyson Airblade	AB 02	10	1399	90
Xlerator	XL-W	12	418	95-100
World Dryer Airforce	J-974	14	260	85
World Dryer AirMax	XM5-974	15	395	83
World Dryer Model A	XA5-974	27	360	82
Electric-Aire	LE1-974	40	150	70
Fast Dry	HK-1800PA	45	91	58

Below is the full text from the Acoustical Society regarding hand dryer noise levels.

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Noise from Energy Efficient Hand Dryers: Is This Progress?

 

Jeffrey Fullerton - jfullerton@acentech.com     

Gladys Unger - gunger@acentech.com

Acentech Inc.

33 Moulton Street

Cambridge, MA 02138

 

Popular version of paper 2pNCc5

Presented Tuesday afternoon, April 20, 2010

159th ASA Meeting, Baltimore, MD

Hand dryers are a popular choice for drying hands in public toilet rooms of many retail and hospitality establishments. They lower costs for proprietors, because new paper towels do not need to be stocked and used paper towels do not need to be clean up or disposed of. 

Within the last decade, new hand dryers have been designed to provide improved hand drying while using significantly less energy. However, numerous people have noted that these new hand dryers are significantly louder than the older, less energy efficient models. These loud hand dryers have been mocked on television (in the series “Community” on NBC) and in cartoons (just try a Google search on “Hand dryer cartoons”). From a practical perspective, the noise from the new hand dryer models frightens infants, interferes with conversations within toilet rooms and in some cases can be disruptive to other nearby rooms.

In a review of various hand dryer models, the manufacturers’ ratings for energy usage show that the new generation of hand dryers uses about ¼ of the energy of an older model hand dryer. The manufacturers also report that the sound levels from these new dryers are only about 30% to 50% louder than the older models.

A survey was conducted to measure the sound levels from several different models of installed hand dryers. During the survey, the measurements were performed with and without hands in the airstream.  This was found to be a significant factor to the loudness of the hand dryer. For some newer hand dryers models, high-speed airflows blowing onto the hands generates substantially higher noise levels.

The following survey results do not lend themselves to precise comparisons between the various models.  The architectural differences between the toilet rooms were not assessed, and may have influenced the sound level from the installed hand dryer.  Nonetheless, the measurements would be similar to those that any person could experience, if they visited the same establishments.  

The measured hand dryers included an older standard efficiency model and two higher efficiency models of radically different designs.  One of the higher efficiency models had a quieter nozzle option, which was also tested.

The first hand dryer is typical of the hand dryer models that have been around for many years and which have been used by many fast food restaurants and other establishments.  Typically, the operator pushes a button to start this model hand dryer. These dryers often require between 30 and 50 seconds to effectively dry wet hands, relying primarily on the hot air from a electric heating element and the users rubbing their hands to perform the drying.

Sound pressure levels from this hand dryer were 82 dBA regardless of whether there were hands being dried within the airstream.

 

 

Figure 1. World Dryer Model A.

The next hand dryer was considered one of the first high efficiency models, introduced back in 2002.  This particular model is noted to produce extremely high-speed airflow, which are about 2 times faster than the older models.  The high-speed airflow blows the water off of hands inserted in the air stream, and can dry hands in about 10-15 seconds. An infrared optical sensor activates this model, so that the dryer only operates when there are hands below the nozzle.

The sound pressure levels from this hand dryer ranged between 89 to 100 dBA, which is significantly higher than the typical models and louder than the manufacturer’s published results.  For this model, the sound pressure levels depended on whether people’s hands were located under the discharge nozzle and how close their hands were to the discharge nozzle.  When the hands are placed a typical 3-4 inches below the discharge nozzle, the sound pressure level at the operator’s shoulder were 100 dBA; the sound pressure level dropped to about 95 dBA (about 30% reduction) when the hands were about 10-12 inches below the discharge nozzle.  With no hands the sound pressure levels was 89 dBA (about 50% quieter than when hands were being dried).

Hands within the stream of the high-speed airflow create significantly higher sound levels than when there are no hands in the air stream.  Because hand dryers work most effectively when the hands are in the airflow, the noise level that users will typically experience might vary between 95 dBA and 100 dBA at this establishment.

The Excel Dryer company has developed a Noise Reduction Nozzle (see Photo 3) that reduces the airflow velocity from the discharge. The manufacturer’s specifications indicated almost a 50% sound level reduction with this alternate nozzle.  But because this larger nozzle reduces the airflow speed, the drying time is increased by 2 to 3 seconds.

 

 

Figure 2. Excel Dryer XLerator^ã

 

 

Figure 3. Original (lefthand) and Noise Reduction Nozzle (righthand).

 

The survey confirmed that the alternate nozzle reduced the noise levels that most users would experience by about 50%.

Of the hand dryer models that were studied, the Dyson Airbladeä model had the most unique design.  This hand dryer differed from other conventional dryers because this dryer uses narrow slits of high-speed air to “wipe” the water off of both the front and back of the wet hands simultaneously.  Photo 4 shows this hand dryer installed in a hotel toilet room. The yellow elements seen in the photo are the narrow slit nozzles for directing the high-speed air at the wet hands, which are inserted, hands facing down, into the opening at the top and then pulled out again.  The manufacturer reports that the airflow passes through the slits at 5 times the airflow speed of an original hand dryer model.  The high-speed airflow clears the water from wet hands in as few as 12 seconds.  This hand dryer was also certified as a hygienic model by an international sanitary organization.

 

 

Figure 4. Dyson Airblade

 

The sound pressure levels of this model varied between 90 dBA with hands in the airstream and 87 dBA with no hands.

There seem to be an endless number of new energy efficient hand dryers being developed, with many of these newer models marketing themselves for their quieter sound levels. These models (and the manufacturer’s reported sound levels) include: the Clean Dry (58-62 dBA) by Toto, Jet Towel (65 dBA) by Mitsubishi, Airforce (83 dBA) and AirMax by World Dryer, and SpeedFlow by Saniflow. 

From a practical perspective, the sound pressure levels of these excessively loud hand dryers can interfere with bathroom conversations. The hand dryer noise can also be an annoyance for nearby spaces.  Noise reduction options, different unique designs and continued alternatives from other manufacturers provide lower noise options for owners and facility managers who may want to select hand dryers for their lower noise emission levels.