Troubleshooting ineffective acoustical assemblies

September 13, 2018

by Jacob Wexler, FDAI

Photos © Legacy Manufacturing

A quick read through any hotel’s online reviews will reveal the most common complaint the hospitality industry struggles with is noise. As anyone who has ever stayed in a hotel knows, the sounds of doors slamming at all hours and boisterous hotel guests in hallways are frequent barriers to getting a good night’s sleep while traveling.

Even during daylight hours, noise can be a major problem in facilities hosting business conferences or catered events. From the clattering of dishes in a nearby kitchen to the raucous sounds of an in-house casino or swimming pool, noise can be an incredibly persistent and difficult problem to solve.

Its presence can not only lead to unhappy guests who can immediately broadcast their dissatisfaction to the entire world via social media, but also the inability to control noise in a facility can result in legal troubles. If a room’s occupants can hear outside noise, then passersby can overhear what is being said inside the room, meaning potentially sensitive information could be inadvertently disclosed and result in breach-of-privacy lawsuits.

However, hotels are not the only buildings suffering from noise pollution. Providing effective sound control is unquestionably one of the most persistent challenges for any type of facility from office buildings and schools to hospitals and law firms. When installed door assemblies fail to deliver the specified level of sound control, both the job and expense of correcting the problem generally fall to the contractors and the distributors responsible for the construction and components. In extreme cases, failure to achieve adequate acoustic control could, ultimately, result in legal liability for specifiers who do not choose the appropriate products to prevent sound transmission.

To minimize both the financial risk and potential liability of ineffective sound control, it is vital to understand acoustics and its implications for door assemblies. Ideally, acoustical engineers will be consulted, particularly for high-risk or high-performance sound challenges.

Troubleshooting common problems
Gaps equal noise and the size of the gap has no bearing on the amount of noise passing through it. Sound waves will travel through any opening with very little loss, so although the amount of air flowing through a gap increases in proportion with the size of the gap, the size of the gap in a sound barrier does not matter. Any unsealed gaps and clearances in door assemblies effectively cancel out the noise reduction benefits of even the highest-rated acoustic doors (Figure 1).

Going back to the earlier example of hotel rooms, the amount of noise passing through a 25-mm (1-in.) gap under the door is roughly the same as having the door open. This is why when a guest is startled awake at 3 a.m. to the sound of someone having a conversation in the hotel hallway, it sounds as though they are standing in the room.

If an acoustical door is not providing sufficient noise control, the very first question to ask is, “What type of gasketing was installed?” In the majority of cases, the source of the problem can be traced back to either poor quality or insufficient acoustical gasketing. For any acoustical assembly to be effective, its gasketing must form a complete, uninterrupted, airtight seal around the head, jamb, and sill. To achieve uninterrupted contact, the gasketing must be installed on the same side of the door and frame. Proper performance also depends on maintaining good surface contact between the gasket and the door edge or frame. This can usually be achieved using compression seals.

The strike plate mounting bracket is applied to the frame to allow a door gasket to be applied in conjunction with a door closer.

Another common source of poor acoustical assembly performance is gaps caused by imperfect door alignment. This is a common problem in newly installed gasketing, but can also surface later as buildings shift and settle and doors cycle through changes in temperature and humidity. The best way to ensure consistent, long-term performance is to select acoustical gasketing with adjustable features and the ability to adapt to any future clearance increases. There are models available on the market enabling the restoration of a sound-tight seal using nothing but a screwdriver.

Beyond gasketing, another area frequently identified as the source of insufficient sound control is the threshold. This is particularly common in situations where the specifier is unsure of the flooring type being utilized in an opening. If an improper selection is made, it can result in a significant amount of space remaining between the bottom of the door and the finished floor, rendering the acoustic door largely ineffective.

One of the most effective solutions to this problem can be found in concealed automatic door bottoms. Although the configurations of this type of seal are endless, the automatic door bottom is activated in one of two ways. First is the standard opening and closing of the door. If the door is closed, the threshold functions as a latch activating the door bottom and allowing the seal to drop down. When the door is opened, the pin hitting against the stop retracts in the
door bottom and seal is then concealed into the housing.

To determine which automatic door bottom mounting option will provide the best acoustical properties, it is imperative to understand the opening. Each opening is different, and every specification writer has their own way of putting together groups of products.

If a door is specified to include a rabbeted threshold, then a surface-mounted door bottom will be more resistant to noise penetration. The rubber portions of the rabbeted threshold meeting the double seal on an automatic door bottom allows for less leaks. The corner gap where the seal meets the jamb, as any specifier or acoustician knows, is always the biggest issue. The installation of a surface-mounted door bottom in conjunction with a rabbeted saddle mitigates the issue of lost sound in corners.

The more innovative approach is to have an electronically retracting door bottom that can be activated with a switch—either a keypad, key switch, or a standard momentary switch with no credential requirements. This feature is extremely useful in settings where sound control is particularly crucial, such as law firms and doctor’s offices, and room occupants are also made aware of the feature and its importance.

The automatic door bottom functions in unison with the rabbeted threshold to provide a secure seal.

Pesky details
As anyone who works in the construction industry is all too aware, there is great truth to the saying, “the devil is in the details.” Even the best products can be rendered wholly ineffective by overlooked details in the specifications or installation process.

Here are some helpful tips for specifiers to ensure the best performance from gaskets and acoustical assemblies. Keep in mind gasketing may have a dual role of sound control and smoke barrier.

Coordination of gasketing and other hardware
It is important to ensure the gasketing specified does not interfere with other hardware on the door. This includes, but is not limited to, pivots, cylindrical locks, electronic hardware, surface-mounted closers, and concealed vertical rods.

Mounting hardware
Mounting hardware locations must be adjusted to accommodate any brackets used on perimeter gasketing. If the surface mounted hardware interferes with the gasketing, mounting brackets should always be used.

To prevent injuries, finger guards and finger protection hardware should be installed on both the hinge and lock side of a door. The extra seal protecting the hinges also prevent tampering and enhance security.

Fire exit or panic hardware must be properly undersized to allow for the mounting bracket over the seal. This instruction is usually given to the contractor or installer as this type of hardware can typically be modified in the field.

Properly under sizing fire or panic exit hardware is important when using brackets to cover acoustical or fire-rated gasketing products. This means, the fire exit hardware or panic exit hardware must be either field trimmed, or ordered shorter than standard, to mitigate any interference between products.

Although proper specification is crucial, the effectiveness of any acoustical assembly depends on proper installation. To ensure the integrity of the gasketing, and thus the entire acoustical assembly, is not compromised in the field, installers should keep the following tips in mind.

Continuous seal
The practice of “notching out” gasketing to create space for hardware is dangerously common as many specifiers and installers either ignore or are unaware of the need for a continuous seal. Breaking this seal creates two potential risks to occupants. The first is a security issue, as the break in the gasketing creates an access point to the secure side of the opening. The second is an even more serious threat to life safety as the door assembly was not tested with the modification. This is of particular concern with fire doors where any breaks in the seal are likely to result in the leakage of smoke into a room.

Cased-open frame
To ensure occupants’ security, particularly in hotel settings, it is imperative to avoid frames without stops, also known as cased open frames. Cased-open frames are not common in commercial settings. However, they do provide flexibility to the specification writer because it allows the ability to accept a larger range of door hardware products. Additionally, cased-open frames are specifically used in conjunction with heavy duty gasketing for openings such as boiler rooms, sound rooms, and studies. These heavy duty acoustical gasketing products must be used with a cased-open frame to ensure specified locks will not require extended spindles or special accommodations. Further, cased-open frames are used in handicap openings requiring a specific clear width of egress.

Due to the design of these frames, the gasketing can be easily removed with a screwdriver, leaving the door unsecured. In a situation where a cased-open frame is already installed, the heavy duty rated gasketing acting as the stop should be mounted with security fasteners to inhibit tampering.

Magnetic locks
Design professionals should be aware magnetic locks can cause interference with the continuous seal. They should only be used with the proper mounting bracket recommended by the manufacturer. Further, any hardware mounted onto or overlapping gasketing must be looked at carefully to ensure the seal has not been compromised, particularly in highly secure openings.

Security brackets
The integrity of the seal is immediately lost once the seal has been cut to allow for a strike or a surface-mounted closer. For this reason, it is mandatory to use security brackets over any type of perimeter seal. Figure 2 (page 80) shows the proper way to install a security bracket to allow for a surface-mounted roller strike to be installed. The security bracket allows for a continuous seal around the opening, which is consistent with the test successfully performed on the opening prior to rating. Additionally, the security bracket helps prevent hardware tampering.

Antibacterial gaskets
In high-traffic areas like hotels, schools, and hospitals, the fight against the spread of microbial contaminants starts at the doors. Installation of antibacterial rubber gaskets can help minimize microbial transmission and maintain a sanitary environment.

Since the science of sound control is so complex, these are only a few of the common challenges specifiers and installers might face when dealing with the problem of noise in any type of facility. Specifiers looking for additional details on gasketing and acoustical assembly requirements should consult the National Fire Protection Association (NFPA) 105, Standard for Smoke Door Assemblies and Other Opening Protectives, and NFPA 101, Life Safety Code.

While many acoustical problems can be avoided by following the tips contained in this article, door and hardware professionals advising designers and owners are strongly encouraged to consult with acoustical engineers during the planning process. Hiring expert installers will also ensure the result of all their planning and specifications is the beautiful sound of silence.

Jacob Wexler, FDAI, is the president of Legacy Manufacturing. He can be reached at[4].  

  1. [Image]:
  2. [Image]:
  3. [Image]:

Source URL: