Evaluating the effectiveness of architectural acoustic design strategies in reducing airport noise transmission into hotels: A simulation-based study

Research objectives

This study pursues three primary research objectives:

Environmental noise and health effects

Environmental noise-induced sleep disturbance represents one of the most common complaints raised by people exposed to noise and can have severe impacts on quality of life and health. ¹⁴ Studies have demonstrated that noise can have immediate effects on sleep including sleep stage changes, total wake time, awakenings, autonomic responses, body movements, and arousal responses. After-effects include decreased daytime performance, cognitive function deterioration, and sleepiness, while long-term effects encompass self-reported chronic sleep disturbance and cardiovascular diseases. ¹⁵

The WHO Night Noise Guidelines summarize the relationship between night-time noise and health effects into four exposure ranges. For night-time noise levels below 30 dB, no substantial biological effects typically occur. Between 30 and 40 dB, effects on sleep begin to manifest, particularly for vulnerable groups including children, the chronically ill, and the elderly. At levels between 40 and 55 dB, adverse health effects increase substantially, and above 55 dB, adverse health effects occur frequently with a high percentage of the population being affected. ¹⁶ For optimal sleep quality, the equivalent sound level should not exceed 30 dB(A) for continuous background noise, and individual noise events exceeding 45 dB(A) should be avoided. ¹⁷

Research on urban noise pollution has documented noise levels significantly exceeding WHO guidelines across multiple contexts. ¹⁸ Sackey et al. ¹⁹ found that noise levels in the Kumasi Metropolitan Assembly, Ghana ranged between 51.86 and 82.87 dB, significantly exceeding WHO 2018 Environmental Noise Guidelines ²⁰ and posing potential health threats including cardiovascular diseases, sleep disruption, and cognitive impairment. Similarly, Iqbal Mazhafizi and Khalid ²¹ documented weekday peak hour noise levels averaging 70.5 dBA in Malaysian urban areas, markedly higher than the maximum permissible sound level of 60 dBA for residential and commercial areas.

Airport noise characteristics and measurement

Aircraft noise presents unique acoustic characteristics that require specific consideration in building design. Aircraft noise and traffic noise generally produce substantial amounts of low frequency sound alongside mid and high frequency components. ²² The Federal Aviation Administration has established the Day-Night Average Sound Level (DNL) as the primary metric for aircraft noise exposure and analysis, calculating average noise exposure over a 24-h period while applying a 10 dB penalty for aircraft operations between 10 pm and 7 am. ²³

The Sound Transmission Class (STC) rating system, introduced in 1970 under ASTM E413, measures a material’s ability to block airborne sound within the frequency range of 125–4000 Hz, correlating with subjective impressions of sound transmission for speech and similar sources. ²⁴ However, this classification method is not appropriate for sound sources with spectra significantly different from speech, such as machinery, industrial processes, and transportation noises including aircraft. ²⁴ The Outdoor-Indoor Transmission Class (OITC) rating was subsequently developed to address low frequency incident sounds commonly encountered near airports, highways, or railway lines, covering a frequency range of 80–4000 Hz and performing adequately where incident sound is broadband and dominated by low frequency noise.^11,24

Architectural acoustic design strategies

The control of noise can be achieved at three different stages: alterations at noise and vibration sources, modifications along the sound propagation path, and addressing sound receivers. ²⁵ For buildings, the mechanism for reducing sound depends on its origin. Sound generated within a room requires absorption; airborne sound originating externally requires insulation; and structure-borne sound requires isolation from the vibration source. ²⁶

Architectural noise control design encompasses multiple strategies. Proper building plan layout involves locating noise-sensitive rooms away from noisy areas where possible, grouping noisy spaces such as living rooms, kitchens, and bathrooms together while situating quiet areas such as studies and bedrooms away from noise sources. ²⁷ Buffer distances around doors and external windows should be maximized to limit potential flanking noise. ²⁷ Balcony design requires acoustical consideration, as standard jutting balconies facing noise sources may reflect sound directly into building interiors.^28,29

Building components can be constructed to reduce noise transmission through decoupling elements, use of absorption materials, increasing mass, damping, or combinations thereof.^30,31 Decoupling stops direct transmission of sound vibration through components by breaking the solid pathway that sound waves follow. Adding insulating materials such as fiberglass is necessary to absorb sound within air cavities that result from decoupling. ³² Mass is critical to soundproofing because heavier components are harder to move and vibrate than lighter alternatives. ³²

Window acoustics

Sound enters buildings through acoustically weak points, with windows representing one of the weakest elements of wall systems. An open or acoustically weak window will severely negate the effect of a strong wall; for example, a wall with an STC rating of 45 containing a window with an STC rating of 26 fcovering only 20% of its area yields a composite STC of only 33, representing a 12 dB reduction.^28,33 Consequently, whenever windows are incorporated into building design, they require acoustical consideration.

For single-paned sealed glazing, STC ratings depend primarily on glass thickness and somewhat on damping provided by sandwiched interlayers. ³⁴ Laminated glazing provides improved transmission loss performance, especially around the critical frequency, though thinner laminated glass with higher STC ratings may be less effective than heavier plate glass at low frequencies. ³⁴ For double-paned glazing, the STC rating depends on both glass thickness and interior airspace depth, with double-wall transmission loss theory predicting higher transmission loss than single panels of the same surface weight when airspaces exceed approximately 19 mm³. ⁵ Triple-paned windows are typically employed when designing for noisy environments like airports with high levels of low frequency noise, as double-paned windows may prove insufficient. ³⁵

Research design

This study employed a mixed-method approach combining qualitative assessment of architectural design features with quantitative simulation analysis. The quasi-experimental methodology utilized computer simulation software to analyze environmental noise conditions and building acoustic performance. Three case study hotels located within a 12.8-kilometer radius of Nnamdi Azikiwe International Airport, Abuja were selected: Peace Media Hotels (1.81 km from airport), Henry George Hotel (3.7 km), and Viclin Diamond Hotel (9.49 km).

Instruments and data collection

Data collection instruments included visual surveys and checklists for documenting building characteristics, hand-held sound level meters for measuring ambient noise levels, and measuring tapes for spatial documentation. Following procedures outlined by the Department of Environment and Heritage Protection, ³⁶ indoor sound level measurements were taken at positions 1 m from walls, 1.2–1.5 m above the floor, and 1.5 m from windows. Outdoor measurements were taken at each corner of the case study buildings and at random points on airport grounds.

Simulation software

Three simulation software packages were employed in this study. SoundPLAN essential 5.0 was used to generate noise contour maps of the airport and case study areas using the equivalent sound level method. This software enables noise simulation for transportation, industry, and leisure noise projects of varying scales.^37,38 INSUL v9.0.19 was employed to predict sound insulation properties of walls, floors, roofs, ceilings, and windows, calculating Transmission Loss in 1/3 octave bands and Weighted Sound Reduction Index values. The software uses robust theoretical models requiring easily obtainable construction information and generally predicts Rw/STC values within 3 dB for most constructions. ³⁹ ODEON v14 was utilized to simulate interior acoustics. Building models created in Autodesk Revit Architecture were imported into ODEON, where transmission loss data calculated with INSUL was assigned to building elements. The software employs the image-source method combined with a modified ray tracing algorithm. ⁴⁰

Wall and window assembly testing

Eight wall assemblies and three window assemblies were simulated using INSUL to compare their acoustic performance. Wall Assembly I represented existing hollow concrete block construction used in case study buildings. Subsequent assemblies incorporated precast concrete, acoustic steel studs, wall cavities of varying widths, fiberglass infill, and multiple layers of gypsum board. Window assemblies ranged from traditional 6 mm single-pane glazing to triple-pane configurations using 10 and 20 mm laminated glass with acoustic resin and argon-filled cavities.

Environmental noise levels at Nnamdi Azikiwe International Airport

Noise measurements and simulations revealed that airport noise levels at Nnamdi Azikiwe International Airport range between 65 and 137 dB, depending on proximity to aircraft operations. Measurements taken near the main noise source (aircraft) yielded sound levels above 120 dB. At measurement points approximately 350 m from the aircraft, daytime levels ranged from 70.4 to 79.1 dB, with nighttime levels 9–10 dB higher. The measurement point closest to the source (5 m) recorded 127.1 dB during daytime and 137.1 dB at night.

Case study hotel noise levels

Environmental noise measurements at the three case study hotels revealed varying exposure levels based on distance from the airport. Peace Media Hotels, located 1.81 km from the airport, recorded daytime external noise levels of 51.6–75 dB and nighttime levels of 61.6–85 dB. The building’s composite STC was 38, and indoor sound levels reached 54 dB. Henry George Hotel at 3.7 km recorded daytime levels of 51.4–70.7 dB with indoor levels of 51 dB. Viclin Diamond Hotel at 9.49 km, primarily affected by road traffic rather than aircraft noise, recorded daytime levels of 49–59.8 dB with indoor levels of 33 dB.

The results indicate that windows were the primary cause of poor sound transmission loss in all case study buildings. None of the hotels had implemented deliberate soundproofing or acoustic considerations during design and construction. The walls (225 mm hollow concrete block) achieved an STC of 53, but when combined with traditional 6 mm glazing, the composite STC dropped to 38.

Effectiveness of improved wall and window assemblies

Simulation analysis of alternative wall and window assemblies revealed substantial potential for noise reduction through material upgrades. Wall Assembly VII, comprising 150 mm precast concrete with right steel studs, 89 mm air gap, fiberglass infill, and two layers of 18 mm gypsum board, achieved an STC of 89 with a total width of 275 mm and surface mass of 393 kg/m². Window Assembly III, using triple 20 mm laminated glass panes with acoustic resin and argon-filled 3 mm cavities, achieved an STC of 52 with a total width of 66 mm and surface mass of 143 kg/m².

Cumulative effect of multiple acoustic strategies

The sequential application of architectural acoustic design strategies demonstrated cumulative noise reduction benefits. Starting from a baseline of 54 dB with existing configurations, improved window assemblies alone reduced indoor levels to 41 dB (24% improvement). Adding improved wall assemblies reduced levels to 38 dB (7.3% additional improvement). Incorporating closed balcony facade design further reduced levels to 34 dB (10.5% improvement). Strategic room zoning positioning rooms away from the noise source achieved 31 dB (17.8% improvement). Finally, upgrading floor and ceiling assemblies to IIC 57 reduced levels in rooms away from the source to 27 dB (15% improvement), meeting WHO guidelines for sleep quality.

The ODEON simulation of room zoning revealed that rooms positioned away from the sound source achieved sound levels 4.7–7.5 dB lower than rooms facing the source. With floor and ceiling assemblies upgraded to IIC 57, rooms away from the source achieved average sound levels of 26.6 dB, well below the WHO guideline of 30 dB for continuous background noise conducive to sleep.

Addressing Research Objective 1: Environmental noise thresholds

The findings confirm that environmental noise levels at Nnamdi Azikiwe International Airport substantially exceed established health guidelines. Measured daytime levels of 65–85 dB and nighttime levels reaching 90 dB in proximity to hotel locations align with patterns documented in other studies of airport and transportation noise. Jacuzzi et al. ⁸ noted that noise in some areas near military aviation facilities exceeded thresholds established by federal regulations for public health and residential land use. Similarly, Sackey et al. ¹⁹ found urban noise levels in Ghana consistently exceeding WHO guidelines, demonstrating the widespread nature of this challenge in developing countries.

The WHO guidelines establish that nighttime noise levels should not exceed 30 dB for continuous background noise and 45 dB for single events to ensure quality sleep. ¹⁷ The existing hotel configurations in this study produced indoor sound levels of 51–54 dB at the two closest properties, substantially exceeding these thresholds. This finding underscores the critical need for deliberate acoustic design in airport-adjacent accommodations, a consideration largely absent from current building practices in the study area.

Addressing Research Objective 2: Effective acoustic design strategies

This study identified several architectural acoustic design strategies with demonstrated effectiveness in reducing noise transmission. The most significant finding concerns the acoustic vulnerability of windows in otherwise adequately performing wall systems. The existing 225 mm hollow concrete block walls achieved an STC of 53, providing reasonable sound isolation. However, the composite STC dropped to 38 when combined with traditional 6 mm glazing, demonstrating how a single weak element can substantially compromise overall facade performance. This finding echoes research by Harvie-Clark et al., ¹² who noted that the most critical facade elements from an acoustic perspective are openings and bays.

The investigation of window assemblies revealed that triple-pane configurations using laminated glass with acoustic resin provide superior performance, particularly at low frequencies characteristic of aircraft noise. This aligns with Long’s ³⁵ observations that laminated glazing offers improved transmission loss around the critical frequency. Notably, the simulation demonstrated that increasing air gap width in multi-pane windows improves mid and high frequency performance but may actually increase low frequency transmission, highlighting the importance of understanding frequency-specific behavior when specifying glazing systems.

The effectiveness of facade design incorporating closed balconies warrants particular attention. While open balconies with absorptive surfaces provided only 1 dB reduction, closed balcony configurations achieved 4 dB reduction by creating absorptive areas with coefficients exceeding 0.9. This finding has significant design implications, as balconies are common features in hotel architecture and can be configured to enhance rather than compromise acoustic performance. Research by Fusaro and Garai ¹³ on innovative noise barrier designs supports the potential for facade elements to contribute meaningfully to sound attenuation.

Addressing Research Objective 3: Quantifying strategy effectiveness

The simulation-based quantification of acoustic strategy effectiveness provides architects and developers with evidence-based guidance for design decisions. The progressive improvements documented demonstrate that achieving WHO-compliant indoor noise levels in airport-adjacent hotels is technically feasible through appropriate material specification and spatial planning. The finding that window improvements alone achieved 24% noise reduction highlights this element as the priority intervention for existing buildings seeking acoustic upgrades. For new construction, the cumulative 50% reduction from baseline (54–27 dB) demonstrates that comprehensive acoustic design can transform indoor environments from health-impacting to health-supportive.

The spatial planning findings merit particular consideration for hotel designers. The 4.7–7.5 dB difference between rooms positioned toward versus away from noise sources represents a substantial environmental quality differential achievable through layout decisions alone. This supports ABCB ²⁷ guidance that noise-sensitive rooms should be located away from noisy areas where possible, extending this principle to external noise source orientation.

Limitations and future research

Several limitations should be acknowledged when interpreting these findings. The simulation-based methodology, while enabling controlled comparison of design alternatives, may not fully capture the complexity of real-world acoustic environments including variable aircraft operations, weather effects, and construction quality variations. Field validation of simulated performance would strengthen the evidence base for design recommendations. The study focused on airborne noise transmission and did not address structure-borne noise that may occur in multi-story buildings through mechanical systems or footfall transmission between floors. Future research should explore OITC ratings and frequency-specific performance criteria for airport-adjacent buildings.