Noisy Buildings – Comprehensive Notes

Abstract

  • Rising urban challenges (densification, contamination, climatic events) spur technological innovation in construction but also increase risk of noise pollution.
  • Paper offers:
    • Preliminary classification of façade-related sound emissions (geophonic, biophonic, anthrophonic).
    • Three Bolivian case studies illustrating each category.
  • Goal: highlight façade-sound interactions as a sustainability criterion.

Introduction – Urban Change, Smart Cities & The Missing Acoustic Layer

  • Cities are densifying; urban population growth amplifies environmental stresses.
  • Smart-city & autonomous-building narratives stress technology, yet often omit sound quality (Kang et al., 2018).
  • Façades as mediators: regulate air, heat, moisture, light and sound (Knaack & Koenders, 2018).
  • Adaptive / automated façade technologies (Attia et al., 2020; De La Barra et al., 2023) add motors, vents, HVAC → potential noise sources.
  • Research gap: mechanisms through which façades themselves generate/induce sounds are under-explored.
  • Key research question: “What are the main mechanisms through which façades generate or induce sound emissions?”

Narrative Literature Review – Method Snapshot

  • Search platforms: Web of Science, Google Scholar, ResearchGate; no peer-review restriction → maximise sources.
  • Inclusion criteria: (a) façade directly involved in sound/noise production, (b) open-access.
  • 21 papers (2012–Jul 2024) retained; methods encountered:
    • Field sound-level & spectral measurements,
    • Binaural/ambisonic recordings for psychoacoustics,
    • CFD & aero-acoustic simulations,
    • Soundwalk questionnaires, VR laboratory studies.
  • Organising lens: Gage et al. (2004) sound categories
    Geophony  ∣  Biophony  ∣  Anthrophony\text{Geophony} \; | \; \text{Biophony} \; | \; \text{Anthrophony}

Façades Emitting Geophysical (Non-Biological) Sounds

Wind-Induced Aeroacoustics

  • Limited literature despite growing high-rise skyline (Čeheľová et al., 2017).
  • Two mechanisms (Chéné et al., 2012):
    • Airborne (whistling/tonal 500–5000 Hz500\text{–}5000\,\text{Hz}; broadband)
    • Structure-borne (vibration → radiation).
Airborne Example Insights
  • Panel edges, perforations, louvres generate vortex shedding → tonal whistling (Blinet et al., 2015).
  • Design mitigation workflow: wind-tunnel + CFD → iterate geometry before construction.
  • Jones & Goehring (2019) highlight CFD as cheaper but computationally heavy alternative; human sensitivity peak ≈\approx speech band.
Structure-Borne Example Insights
  • Jones & Goehring (2018): parametric CFD of perforated panels → machine-learning model predicts risk map across façade.
Other Geophysical Sources
  • Thermal cracking (wood, metal) from expansion/contraction.
  • Precipitation impact noise (rain/hail) – frequency & level depend on material impedance.
  • Artistic precedent: “Hof der Elemente” (Dresden, 2001) funnels rainwater to create
    sounds; anecdotal video reviews deem effect non-musical.

Façades & Biophonic (Living) Sounds

  • Façades don’t vocalise but can host/support organisms producing sound (Pijanowski et al., 2011).
    • Insects 3–8 kHz3\text{–}8\,\text{kHz}, frogs 2–5 kHz2\text{–}5\,\text{kHz}, birds 2–12 kHz2\text{–}12\,\text{kHz}.
  • Vertical greenery / green walls foster avifauna & insect activity → restorative auditory benefits (Cardinali et al., 2023).
  • Empirical gap: few real-world studies connecting green façades, health & soundscape (Al-Kayiem et al., 2020).
  • Soundwalk finding (Detmold 2023): ivy-clad façade perceived as quieter & “more natural” though SPL\text{SPL} matched control street.

Façades & Anthrophonic (Human-Origin) Sounds

Mechanical Systems

HVAC (Split-Unit Compressors)
  • Dominant A/C type in EU; visual & acoustic nuisance (Masullo et al., 2021).
  • Field SPL near source ≈57 dBA\approx 57\,\text{dBA}; VR experiment shows sound × visibility interaction ↑ annoyance.
Motorised Shading / Adaptive Skins
  • Case: “Riegel” building (TH OWL campus) – louvre motion raises façade-proximate SPL to ≈62 dBA\approx 62\,\text{dBA}, drops ≈20 dB\approx20\,\text{dB} at 15 m.
  • VR lab: static façade perceived “pleasant/calm”; moving → “chaotic/annoying”.

Electroacoustic / Digital Systems

Loudspeaker-Based Soundscape Interventions
  • Most common intervention type in Catalogue of Soundscape Interventions (2023); façade-integrated examples still rare → research opportunity.
Media Façades
  • Building surfaces as interactive AV screens (Haeusler 2009). Recent mobile interfaces (Boring et al., 2011) enable user sound input.
Sound Masking & Active Noise Cancellation (ANC)
  • Masking: feed broadband/coloured noise via speakers (trad. interiors).
  • ANC: sense external noise, emit inverse waveform →\rightarrow destructive interference.
    • Schüco ASE 80.HI sliding door prototype (BAU 2019): microphones + speakers concealed in wall, activate when door opened.

Case Studies – Santa Cruz de la Sierra (Bolivia)

(Climate: tropical savanna Tavg≈25 ∘CT_{avg}\approx25\,^{\circ}\text{C}; wind 10–20 km/h10\text{–}20\,\text{km/h} gusts >50 km/h>50\,\text{km/h})

Ambassador Business Center (Geophonic – Wind Whistling)

  • 90 m concrete tower, metal mesh on two façades; surrounded by low-rise → high exposure.
  • Residents reported “whistle/buzz” during 2015–16; likely mesh-induced vortex shedding.
  • 8 qualitative interviews (Dec 2023): 5/8 aware of sound; perceptions – 1 pleasant, 1 annoying, 3 neutral.
  • Next steps: capture event audio, spectral analysis, larger ISO 12913 soundscape survey.

Courthouse (Anthrophonic – HVAC Noise)

  • 24-storey, fully glazed north façade; hundreds of wall-hung split compressors in shaft masked by black mesh.
  • Ground-level monitoring: compressor noise audible on D’Orbigni St.; less perceptible across plaza due to traffic & street activity masking.
  • Research needs: SPL mapping, neighbour soundscape interviews, potential retrofits.

Aqua Tower (Anthrophonic – Multimedia Façade)

  • Residential tower with 25 m × 2 m LED ribbon + embedded loudspeakers along shopfronts.
  • Plays short branded audio loops controlled by building admin – differentiates property market image.
  • Unknown acoustic impact on pedestrians/residents → proposed measurement & perceptual study.

Discussion – Toward a “Façade Noise Footprint”

  • Classification confirms façades influence city soundscape via multiple mechanisms beyond reflection/absorption.
  • Smart-city regulations (e.g.
    EU Environmental Noise Directive) emphasise traffic/industry; façade-specific sources largely unregulated.
  • Conceptual transfer: noise footprint (aviation) → require architects/façade engineers to quantify façade emission impact during design.
  • Outdoor façade acoustics lack unified standards unlike thermal, daylight or ventilation performance.
  • Integrating soundscape (ISO 12913) into façade multi-criteria workflows (Bianchi et al., 2024) supports health & wellbeing.

Recommendations for Stakeholders

  • Architects/engineers: include aeroacoustic & mechanical noise simulation early; test mitigation (geometry tweaks, damping, ANC).
  • Urban planners: incentivise green façades to harness biophonic benefits; evaluate trade-offs (maintenance, allergens).
  • Policy makers: develop façade noise footprint guidelines; align with smart-city sensor networks for real-time monitoring.
  • Researchers: expand empirical database – especially media façades, ANC façades, precipitation-art façades.
  • Manufacturers: provide acoustic data for façade components (meshes, louvres, shading motors, HVAC mounting kits).

Key Numerical & Technical Reference Points

  • Human auditory sensitivity peak: 500–5000 Hz500\text{–}5000\,\text{Hz}.
  • Audible spectrum: 20 Hz≤f≤20,000 Hz20\,\text{Hz} \le f \le 20{,}000\,\text{Hz}.
  • Wind-induced façade whistling often tonal within speech band.
  • Detmold shading system SPL rise: ΔLp≈62 dBA@1 m\Delta L_p \approx 62\,\text{dBA}@1\,\text{m}.
  • Split-unit compressor field level: Lp≈57 dBAL_p \approx 57\,\text{dBA} (Masullo et al.).
  • Distance attenuation (Riegel case): 20 dB20\,\text{dB} reduction at 15 m15\,\text{m}.

Selected Cross-Lecture / Real-World Connections

  • Aeroacoustics principles parallel to automotive side-mirror whistle studies; same vortex shedding physics.
  • Green façade sound benefits align with restorative environmental psychology (Attention Restoration Theory).
  • ANC façade module analogous to headphone noise-cancellation but scaled; raises energy & maintenance questions.
  • Media façades converge architecture with UX design; interdisciplinary teams (HCI, acoustics, lighting) required.

Ethical & Philosophical Considerations

  • Acoustic justice: façade-generated noise often affects non-occupants (public realm) who lack agency over design.
  • Transparency: Should developers disclose expected façade noise footprint as part of environmental impact reports?
  • Sound as cultural layer: opportunity to craft positive identity (soundmarks) vs commodified advertising (Aqua Tower).

Future Research Avenues

  • Standardised façade aeroacoustic test rigs (wind-acoustic tunnels + psychoacoustic metrics).
  • Longitudinal studies on biodiversity & green façades ↔ urban soundscape wellbeing.
  • Efficacy & acceptability of outdoor ANC under variable wind / diffraction conditions.
  • Large-scale deployment of IoT acoustic sensors → dynamic city-level façade noise mapping.

Reference Highlights (Abbreviated)

  • Albino et al. 2015 – smart-city definitions.
  • Balderrama et al. 2022 – systematic review on façade acoustic effects.
  • Bianchi et al. 2024 – multi-criteria façade design.
  • Gage et al. 2004 – geophony/biophony/anthrophony taxonomy.
  • ISO 12913-1 2014 – soundscape framework.