The challenge of guest room acoustics in hotels

March 13, 2018

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By Niklas Moeller
Guest room acoustics pose a significant challenge for hotels, with noise regularly topping the list of complaints across all property types. Unwanted sounds irritate guests during the day, prevent them from relaxing in the evening, and affect their ability to sleep.

Noise issues can be attributed to a variety of interior and exterior sources, including guest activity (e.g. talking, arguing, or partying), electronics or appliances (e.g. televisions, alarm clocks, or HVAC systems), hallway sounds (e.g. ice machines, elevators, or slamming doors), and the building’s surrounding environment (e.g. if the property is located beneath an air route, adjacent to a freeway, or near a nightclub).

For hotels, the financial impact of a noise problem can be substantial. Following an unpleasant stay, dissatisfied guests are less likely to return to a property and more inclined to post a negative review online. As a result, the hotel’s reputation and bookings can suffer. A TripAdvisor survey found 55 per cent of people booking hotel rooms specifically read online reviews mentioning sleep quality before making a reservation. There are also direct costs associated with appeasing unhappy visitors, such as offering discounts and vouchers.

An incomplete approach
Noise problems persist within these facilities for two reasons. First, as demonstrated by the JD Power North American Hotel Guest Satisfaction Survey, the majority of guests do not complain to hotel staff when disturbed by noise. Instead, they simply decide not to return to the property, leaving many hotels unaware of the problem and its impact. Second, when aware of this issue, the majority of hotel managers attempt to address it in pursuit of an unachievable goal: silence.

As illustrated above, noise issues can be attributed to a variety of interior and exterior sources.
Photos courtesy KR Moeller Associates

To block exterior noise and prevent interior transmission, property managers may increase construction standards for walls, windows, floors, and doors, or simply attempt to quiet noise sources from within the rooms. (Low background sound levels can place limitations on a hotel’s procurement options when sourcing equipment meant for guest rooms. In a 2005 article in Hotel & Motel Management magazine, Mark Holzberg, president of minibar maker Bartech Systems, noted the background noise level in guest rooms is around 31 dBA. As a result, his company needed to engineer exceedingly quiet equipment to avoid guest complaints.) Although these methods are a necessary part of an effective acoustical plan, it is impossible to completely eliminate all noises. (Some hotel operators have tried implementing policies to keep guests with lower noise tolerance away from any noisier areas/guests [e.g. providing business-only or family-friendly floors], while others have implemented quiet hours or offered guests earplugs. However, guests should not have to bear the burden of poor acoustical planning.) Further, the lower the room’s background sound level becomes as a result of these initiatives, the easier it is to hear any remaining noises—even those at low volume.

In fact, hotel owners/operators might be surprised to learn the noise peaks to which guests are subjected inside their rooms are often not much greater than 40 dBA. While one would not usually describe these sounds as ‘loud,’ they are disruptive in the context of the low interior ambient levels exhibited by most properties, which are typically only 28 to 32 dBA—even lower in mid- to high frequencies. (By way of example, this author recently performed measurements in a residential bedroom because the occupant had complained to town officials about traffic noise from a nearby road. The occupant was certain volumes exceeded local regulations. However, testing revealed when traffic passed by the house, peak volumes were only 40 to 41 dBA. The occupant perceived them as higher due to the significant 14 to 15 dBA change in volume from the bedroom’s low background sound level of 26 dBA.)

Guest rooms typically exhibit very low ambient—or background—sound levels of around 28 to 32 dBA. By comparison, a quiet library is 30 dBA and normal conversation is 50 to 60 dBA. Given the decibel scale is logarithmic, the difference between these two levels is much greater than most people would assume from considering the numbers alone.
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What disrupts sleep?
Though little independent research has been done on noise levels and sleep patterns in hotels, studies conducted in healthcare, home, and military environments demonstrate volume variations disrupt sleep. In other words, it is not the overall volume or highest level that determines whether or not disturbances occur, but rather the degree of change from baseline to peak. (See M.L. Stanchina et al’s article, “The Influence of White Noise on Sleep in Subjects Exposed to ICU Noise,” in the sixth volume of Sleep Medicine.) As the change in volume between a relatively low background sound level and intermittent noises increases, so does the likelihood of sleep disruption. Essentially, the more significant the change, the harder it is for individuals to ‘block out’ the noise. This is why, for instance, bursts of noise from infrequent traffic are far more disruptive to sleep than the constant sound produced by high-density traffic. Individuals tend to sleep better in environments with continuous noise of a certain level than in environments with intermittent noise of the same average level. (See Andy Coghlan’s August 22, 2007 article, “Dying for some quiet: The truth about noise pollution,” on the website[4].)

Sleep can be affected by noise in a number of ways, including delayed onset, shifts in sleep state, and awakenings. Disturbed sleep caused by unwanted sounds can prevent individuals from progressing through the natural stages of the sleep cycle and result in raised blood pressure, increased heart rate, and other physiological effects. Sleep disruption can affect mood, appetite, energy levels, and concentration.

In hotels, noise can also have detrimental effects while guests are awake, impacting their enjoyment of the property as well as their overall sense of privacy. Beyond general annoyance, when a sound or voice enters an occupant’s space (e.g. overhearing a loud television in a neighbouring room or a phone call in the hallway), the intrusion can violate his or her sense of physical separation. The guest may also become self-conscious about his or her own level of privacy.

Without sound masking, this guest room has an exceptionally low ambient level of 21 dBA (red line). With sound masking (green line), it is 45 dBA and also conforms to the standard National Research Council (NRC) masking spectrum (grey lines)—a curve designed to balance acoustic control and comfort.
Images courtesy KR Moeller Associates

Controlling background sound
Out of frustration, guests often try to use their rooms’ HVAC systems to drown out unwanted noise. Given these systems were not designed for this purpose, the units cycle on/off and do not produce the correct sound spectrum or level to be effective. When used in excess, energy consumption and maintenance costs also increase.

To reduce the number of disruptions caused by noise, hotel management has to control the frequency and magnitude of volume changes within the space. While achieving complete silence is impossible, providing a higher and more consistent baseline level can easily be accomplished.

Controlling background sound levels is best achieved by introducing sound masking technology to each guest room. The sound is typically compared to softly blowing air, but unlike ventilation and ‘white noise’ machines/mobile applications, a commercial-grade masking device produces a sound that follows a particular spectrum, engineered to balance acoustic control and occupant comfort. The sound is produced over a high-quality loudspeaker and adjusted via fine volume and frequency controls.

Adding sound to a space may run contrary to most people’s understanding of how to control noise, but the premise is simple: any noise registering below the new background sound level is masked, while the impact of those above it is lessened because the degree of change between the baseline and any volume peaks is smaller. As there are no fluctuations or patterns in the masking sound itself, it does not affect comfort or sleep.

This graph shows variation in guest room sound levels over time (i.e. dynamic range). With masking off, the ambient level is just below 30 dBA. The large volume spikes of nearly 15 dBA are from a conversation in the corridor. With masking on and set to 44 dBA, the variations are significantly reduced, thus creating a more comfortable acoustic environment.

Most noises entering guest rooms are near or below 40 dBA, meaning they are easily muted by a relatively low level of masking (i.e. 40 to 45 dBA). Though this will not always completely cover an offending noise, this level will substantially reduce its disruptive impact. As noise can span a wide range of frequencies, the masking device must be capable of outputting sound down to the 100-Hertz (Hz) level. Humans are capable of hearing sounds as low as
20 Hz, but these lower frequencies sound rumbly. With sound masking, specifiers are aiming for the ‘sweet spot’—a level low enough to cover a wide range of noises without dropping so low as to introduce an element of acoustic discomfort. If the output is incapable of matching the frequency of the noise, the sound will not provide as great a degree of masking benefit as expected.

Sound masking is already on when guests arrive and is set at a default level selected by hotel management. Occupants are able to use a surface-mounted control pad or wall-mounted dial to adjust the volume, which allows them to control their rooms’ ambience the same way they control temperature and lighting. (While control can potentially be offered via a mobile phone application, blue-light devices have been shown to negatively impact sleep by suppressing melatonin production. A manual dial is easy for all guests to use, regardless of their technological proficiency.)

A surface-mounted control pad or wall-mounted dial allows guests to adjust their rooms’ ambiance as they would temperature and lighting.

Case studies
Properties under the Hilton, Marriott, Fairmont, Ritz Carlton, and Dream Hotel brands, as well as the Fogo Island Inn, have successfully installed the type of sound masking equipment used to improve speech privacy and control noise in commercial offices.

For example, the Roxy Hotel Tribeca (formerly Tribeca Grand Hotel) in New York City had a significant noise issue, attributed to an eight-floor atrium, which was open to all floors and featured a lounge on the lower level. Sound from the lounge travelled up the atrium, disturbing guests in their rooms. In 2003, the hotel conducted a two-floor trial of sound masking and, by 2005, had expanded it to cover the entire property. (For more information, see Heather Gunter’s May 7, 2009 article, “Construction methods help combat noise,” on the website[8].) Since its introduction, guests have praised the technology in hundreds of unsolicited positive online reviews.

In 2009, conscious of potential noise issues from an adjacent freeway, hotel management at Springhill Suites by Marriott in Roseville, Calif., implemented sound masking in 15 rooms across one wing of the facility. A single loudspeaker was installed in each room, along with a wall-mounted dial, which allowed guests to set the unit’s volume to their liking. After implementation, the hotel distributed guest satisfaction surveys and received overwhelmingly positive feedback. The hotel’s general manager, Micael Jeffries, noted many respondents had detailed previous negative experiences related to unwanted noise in hotel rooms and were impressed with the effectiveness of masking.

However, for existing properties, the cost and complexity of implementing this type of installed system is often prohibitive. In these cases, a ‘bolt-on’ (i.e. attached to the back of a TV, wall, or furnishing) rather than a ‘built-in’ (i.e. installed using a cut-through in the wall or ceiling) masking solution is preferable, as its implementation does not interrupt occupancy or depend on installation conditions.

Noise problems persist within hotels and guest rooms despite increased construction standards because these issues cannot be efficiently addressed using sound isolation and reduction alone. While effective at reducing noise at its source and volume peaks, these techniques lower overall background levels. Thus, any remaining sounds vary more greatly from the remaining background and can be more disruptive.

Introducing sound masking in hotels allows guests to control both the volume and nature of ambient sound, demonstrating a proactive approach to dealing with noise. Alternatively, if a hotel identifies problems after opening, this solution is far more cost-effective than pursuing further structural improvements or replacing equipment, particularly given the introduction of ‘bolt-on’ commercial-grade masking solutions. That said, in the hospitality industry, it is far better to prevent a poor experience than try to fix one after the fact.

Niklas Moeller is the vice-president of K.R. Moeller theAssociates, manufacturer of the LogiSon Acoustic Network and MODIO Guestroom Acoustic Control. He has more than 25 years of experience in the sound masking field. Moeller can be reached via e-mail at[9].

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