Silence: A New Luxury Offering for Hotels and Resorts
By Lawrence Adams Principal, Lawrence Adams Architect | November 2024
Applications of innovative new technologies for acoustic engineering, fueled by advancements in AI, will provide guests with the transformative benefits of pure luxurious silence.
As hotel companies strive to distinguish their brands at the ultra-luxury end of the spectrum, they promote opulent accommodations in splendid locations, dote on patrons with eloquent bespoke services, and offer superb culinary experiences.
Some may deliver stimulating adventures in the jungle, in the mountains, or in the desert. Still others serve up a genuine state-of-the-art health-promoting experience of holistic wellness and therapeutic well-being. But for those patrons who are starved for simple solitude in a tranquil setting away from the din and cacophony of tumultuous urban life, the offer of a respite of pure sustained silence has great appeal.
The Noise Problem
The number one complaint for all hotel segments has historically been noise. In surveys the most prevalent reason for hotel guest dissatisfaction has been intrusive sound. Noise complaints have, by a large margin, outpaced poor service, deficient cleanliness and hygiene, inadequate heating or AC, uncomfortable beds and bedding, bad lighting, and room size. For hotels that suffer from noise complaints, they have consistently led to poor reviews and consequently poor bookings.
In my recent article on sleep science (Beyond Magic Fingers: Sleep Science forHotels and Resorts , Hotel Business Review, 5/12/24, by Lawrence Adams), I point out that the primary environmental reason for sleep disruption for hotel guests comes from nighttime noise from loud AC units, street noise, slamming doors, noisy neighbors, and poor plumbing insulation. But the problem goes beyond sleep deprivation and even beyond the guestroom.
Noise problems in hotel public spaces have many sources. Dear readers, who among us hasn’t had to ask a waiter to turn down the music volume in a restaurant. Or had to suffer through crappy amplified live music emanating from the hotel bar as it spills into the lobby lounge. Or strained to hear a speaker in a meeting room due to ambient noise radiating from the pre-function lobby.
Most of these problems can be solved by investing in proper design and quality construction such as double-glazed windows, sound attenuation materials in walls, ceilings and floors, acoustic gasketing at doors, insulated plumbing design and sound dampening of high-grade mechanical equipment. Some of these solutions may be expensive, but the investment should pay off in the long run with repeat bookings from satisfied customers.
The architects for the New York Four Seasons designed the guestrooms with several noise reduction features including triple glazed windows, sound isolating demising walls, additional acoustic insulation of HVAC and plumbing systems and vibration dampening floor underlayment. As an extreme precaution the noisy gas-fired emergency generator was built in a bunker-like sound isolation chamber mounted on springs and with mufflered exhaust to prevent disruptive noise from reaching guests during the monthly testing of the generator. The heavy spin-cycle tumblers of the hotel laundry were mounted on spring supported isolation slabs to prevent vibration from traveling up the concrete structure.
The Quiet Room® label is achieved by meeting stringent qualifications for sound control in hotels.
Noise and Stress
Excessive noise exposure has proven to significantly impact human stress levels and overall mental and physical health. Even low levels of environmental noise may trigger a physiological stress response affecting the sympathetic nervous system leading to increased heart rate and high blood pressure. Prolonged exposure to noise pollution can lead to hypertension, vascular damage and increased risk of heart disease. In addition to physical health problems, chronic noise exposure is associated with a number of mental health issues including increased anxiety, cognitive impairment and depression.
Sleep deprivation can of itself lead to significant physical and mental health problems. Physical problems from chronic sleep disorders may include a weakened immune system, weight gain, hormonal imbalance and cardiovascular issues. Effects on brain and cognitive function from insufficient sleep could include mental fatigue, impaired alertness and memory, mood changes and slowed reflexes. Severe cases of sleep deprivation can even lead to hallucinations and psychotic episodes. While we wouldn’t expect a few nights of sleep disruption to cause the more extreme effects described here, a guest who experienced a couple of sleepless nights might not be safe to drive or sharp enough to attend an important sales meeting.
In a Duke University study, researchers proved that silence is healthy for the brain. The study looked at exposure to a variety of different sounds in laboratory mice and concluded that silence was the only stimulus that promoted new neuron growth through neurogenesis. The effect of silence was found to increase cell density in the prefrontal cortex and hippocampus facilitating memory, creativity and new neural connections. Silence, therefore, promotes cognitive health.
Quite Zones
In addition to investing in basic design solutions and noise reduction technology to ensure toxic noise issues are effectively addressed, some upscale hotel brands are beginning to recognize the value of creating quiet, peaceful settings for their guests. Some have adopted marketing slogans like Silence is the New Luxury and have begun implementing programs to provide this new offering.
Many brands have designated quite zones and quite floors in their properties. Hilton, Marriott and Hyatt now have some form of quite zone provision in a collection of their hotels. They have found that some guests are willing to pay more to stay in a more serene part of the hotel that is set apart from the more boisterous activity areas of the lodging. Often these zones will be located on the upper floors or remote wings of the building that afford more distance from noisy public spaces and loud sounds from the street below. These quiet zones may schedule limited times for housekeeping and maintenance to avoid disturbing guests during the evening and early morning. Large groups and families with young children are frequently the source of unwanted noise and so may be restricted from these quite zones.
Enhanced sound control measures may be implemented in these zones and include sound absorbing panels, furnishings and materials in the rooms, double or triple glazed windows, auto-closure devices on doors to prevent slamming, staggered-stud wall construction to prevent vibration transmission and the introduction of soothing white noise to mask unwanted sounds.
A new international rating system developed in the Netherlands by Knowledge Centre Sound Insulation (KGI) provides certification to hotels and resorts that meet standardized minimum criteria for excellence in acoustical design and operations. The Quiet Room® label is achieved by meeting stringent qualifications for sound control in hotels, including measurements for reverberant sound period (moment when sound level drops below 60 dBA), airborne noise insulation between rooms (must be less than 30 dBA) and service equipment sound level for ventilation, refrigerator and toilets (must be below 30 dBA). The Quiet Room® Design & Build Guide provides certification of building materials, for example, the DRS Sound Supreme Board is certified for insulation of internal and exterior door systems. As of this writing there are over 150 hotels worldwide that carry the Quiet Room® QR label including The Hilton Munich Airport (Germany), Ramada Apollo Amsterdam Centre (Holland) and the Tokyo Station Hotel (Japan).
Silientium’s Personal Sound Bubble (PSB) system can control ambient sound waves so a space can be divided into independent listening zones.
Mindfulness and Silence
In an article I wrote for Hotel Business Review in 2017 titled The Wellness Trendin Hospitality , I wrote, Medical studies confirm that beneficial silence increases awareness, sharpens concentration, kills stress, facilitates healthy sleep cycles, combats fatigue and depression, normalizes blood pressure, and boosts creativity. I added, Emphasis on silence as a valuable and marketable wellness commodity has found its way into restaurants that offer silent eating, and airports that have eliminated loudspeakers announcing gate times. In hospitality, we are seeing the emergence of the "Silent Spa," such as the one at Therme Laa Hotel in Austria that advertises "only the sound of gently lapping water.”
In keeping with the growing trend of providing Wellness environments and programs in hotels, many properties are supporting the goals of Mindfulness by providing guests with serene places that promote relaxation and reflection. With a focus on holistic health and mental wellbeing, which is at the core of the mindfulness concept, they look to provide an escape from the constant stimulation and stress of urban life. The pursuit of mindfulness involves attaining awareness and sustained focus of the present moment which requires calm and peaceful surroundings to effectively cultivate.
Zen gardens, meditation rooms and quiet zones are frequently offered to help guests realize health-promoting tranquility and stress reduction. Digital detox initiatives in some resorts encourage guests to disconnect from technology to achieve mindfulness by instead connecting with tranquil surroundings and calming experiences. Silence is an essential component of mindfulness where guests may find respite from noise and chaos of daily living, fostering mental wellbeing and attaining broader wellness goals.
The Science of Silence
The ear is an amazingly sensitive organ that is responsible for hearing and balance. If stimulated by the slightest sound, the tiny bones of the middle ear, when transmitting sound from the eardrum to the inner ear, vibrate by less than the diameter of a hydrogen atom. Even in the absence of sound, miniscule vibrations of molecules excite different parts of the auditory system. In complete silence the apparatus may perceive molecular motion and hear the hiss generated by thermal agitation of the eardrum and the hair cells in the cochlea.
The scientific methodology for studying the phenomena of silence for acoustic testing is generally grouped in three categories, namely, Reverberation Chambers, Natural Silent Environments and Anechoic Chambers.
Reverberation Chambers are used for testing sound absorption of materials as noise travels between spaces by amplifying sound wave reflections and measuring the time period for acoustic energy reduction. The process is used to determine the sound absorption coefficient of materials in noise reduction.
Natural Silent Environments are generally found in remote locations like Antarctica where the absence of sound generation from wind, running water or wildlife results in an extreme experience of silence. In addition to remote polar regions, deep forests and jungles, isolated mountain valleys and underground caves also provide unique testing capabilities to study environmental noise, real-world outdoor noise propagation and natural sound absorption from vegetation and terrain.
Anechoic Chambers are designed for maximum sound elimination. The anechoic chamber at Orfield Laboratories in Minneapolis, according to Guinness, is the quietest place in the world, with a record-breaking background noise reading in 2021 of -24.9 dBA. The test chamber is mounted on springs to prevent unwanted vibration and with every surface covered with large wedges of grey foam, including the floor beneath a wire trampoline. Subjects report that when holding their breath, the only sound they hear is their own heartbeat, the low pulsing of their blood circulation and even their eyelids blinking.
It should be noted that prolonged periods of complete sound isolation can lead to an experience of sensory deprivation which can cause hallucinations and emotional distress. Subjects in the Orfield Lab have begged to leave the anechoic chamber after less than an hour due to an experience of disorientation and heightened anxiety. For some, when left with no sounds to distract one from inner voices, silence, through emotional amplification, can be deafening!
Stem Ceiling creates an audio fence around the meeting participants as an adjustable invisible bubble that uses noise cancelling microphones to block outside noise.
Future Technology of Silence
As written in my article on Sleep Science mentioned above: Innovative new acoustic systems that employ cutting-edge noise cancellation technology can be made available to guests so that they can bring a high level of sound control to their room. Silentium Ltd. is an audio technology company that specializes in developing innovative noise reduction products. Silentium Active Noise Control (ANC) is an active noise reduction technology that is literally the wave of the future. This technology generates a sound wave to cancel out offending sound waves and can reduce noise by 90%.
Future applications of this technology in hotels may provide guests with the ability to shape the sound levels in their rooms to suit their disposition. A guest’s audio experience may be delivered by Silientium’s Personal Sound Bubble (PSB) system that can control ambient sound waves so a room can be divided into independent listening zones. It should be possible to create a PSB over the bed while a companion is conducting a business call in another part of the room.
Noise cancellation technology for headphones and earbuds is far more advanced than room-level noise cancellation. Technology that addresses ambient noise in a physical room presents significant control issues. AI may someday solve the essential problem of calculating and generating inverse sound waves for a large, dynamic space given that its calculations will require immense computational power.
Products for masking sound with white noise do not actually reduce noise levels and so do not contribute to the perception of pure silence. That said, devices for blocking outside noise in a conference room setting have real acoustical value. One such innovative device is the Stem Ceiling from Shure, which hangs from the ceiling over a conference table and creates an audio fence around the meeting participants as an adjustable invisible bubble that uses noise cancelling microphones to block outside noise and keep the focus on attendees’ voices.
The Quiet Room® Foundation is in development of an app named Quiet Hotel Room Reality where hotel guests will be able to experience the sound reduction qualities of different acoustical products with a built-in audio device. The app will use Microsoft HoloLens augmented reality technology to demonstrate soundproofing solutions for hotel rooms with an immersive audio-holographic experience. Acoustic holography is a method for capturing and reproducing the three-dimensional distribution of sound waves in real time with holographic imagery.
AI is evolving new tools for high level visualization for advanced acoustic engineering. Similar to acoustic holography for depicting sound waves, acoustic engineers are beginning to employ 3D Impulse Response Management to create 3D visualization of guestroom and hotel public space acoustics to identify sources of offending noise intrusion and reflection. The process measures and analyzes sound fields in terms of magnitude, time and direction of reflections. Mesh-based neural network platforms such as MESH2IR generate 3D representations of acoustic impulse responses within a defined 3D environment, utilizing the same set of tools that Generative AI algorithms are beginning to use for generating 3D architectural form (Generative AI and Design Process for Hotels, Hotel Business Review, February 2024, by Lawrence Adams).
There are new products developed every year that address sound attenuation and control. Advances in glazing technology have led to acoustic glass that, while currently more expensive, is more effective than triple glazing and can be installed more easily in less bulky window frames. New innovations in acoustically absorbent fabrics are finding their way to the market of hotel designers and furniture manufacturers.
Without getting into a deep discussion on the science behind metamaterials, suffice it to say that AI advancements and cutting-edge research in the creation of extraordinary artificial materials are advancing at a dizzying pace. These engineered materials contain smart properties capable of manipulating, absorbing and bending electromagnetic waves beyond what is possible with natural materials. By utilizing negative refractive indices, scientists are able to create products like a flat lens for optical devices leading to eyeglasses with lenses that are a fraction of the weight and thickness of conventional lenses.
Boston University researchers are working on acoustic metamaterials designed to manipulate sound waves at levels that can actually cancel out sound so effectively that it essentially creates an acoustic black hole. Advancements with electromagnetic shielding that guide or scatter acoustic waves may soon lead to sound absorption technology so efficient that a person without headphones or earbuds will be able listen to music without disturbing the person next to them.
Conclusion
We expect to see continued innovations and advancements in AI technology for sound control that apply to the acoustical design of hotels and resorts. As the economies of this technology become more feasible and affordable, guests seeking the transformative benefits of silent hospitality will find them available for all lodging segments. Excellence in acoustical engineering design will not be limited to guestrooms but will improve guest experience in all areas of the hotel or resort.
As resulting guest satisfaction and repeat bookings grow, developers, investors and operators will find their investments in this new technology to have significant benefit to their bottom line and will come to realize that indeed Silence is Golden.
Mr. Adams
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