SPACE 01

HPT – Ground Floor Corridor – ETH Hönggerberg

The corridor in the HPT building at ETH Hönggerberg presents a compelling study in industrial minimalism, where high-performance materials dictate both the visual and auditory experience.

Volumetric Description

The space is characterized by a strong sense of linear perspective and rhythmic modularity.

• Geometry: It is a long, tall, and relatively narrow “canyon” defined by a series of repetitive structural bays. The exposed concrete pillars create a deep architectural grain, while the white, flush-mounted cabinetry panels provide a clean, smooth counterpoint
• Materiality: The palette is dominated by “hard” surfaces—fair-faced concrete, terrazzo flooring, and metal ceiling panels. These materials suggest durability and precision, typical of a high-tech research environment.
• Scale: The high ceiling and the continuous light fixtures pulling your eye toward the end of the hall make the volume feel expansive yet disciplined. The glass doors at the far end offer a visual release, preventing the long corridor from feeling claustrophobic.

Acoustic Analysis

The acoustic signature of this corridor is defined by its high reflectivity and long reverberation time. Because the walls, floor, and ceiling are mostly non-porous, sound waves bounce repeatedly before decaying.

Distance	Acoustic Observation
0m – 2m	The voice is “dry” and intimate. You can hear the high-frequency “crack” of the clap clearly, with immediate, sharp reflections from the nearby concrete pillars.
4m – 6m	The Pre-Delay becomes noticeable. There is a distinct gap between the initial clap and the wash of sound returning from the walls. The voice begins to lose some “presence” as it blends with the room’s resonance.
8m – 10m	The space feels its largest here. The clap triggers a significant reverberant tail, sounding like a “slap-back” echo. The speech becomes slightly less intelligible as the “wet” sound of the room begins to compete with the “dry” direct sound of the voice.

How the Space Feels

The combination of the cold concrete and the echoing acoustics creates an atmosphere of clinical “stillness.” * Atmosphere: It feels professional, quiet, and perhaps a bit intimidating. Every footstep or whispered conversation is amplified by the hard surfaces, making one hyper-aware of their own movement through the space.

• Visual-Acoustic Sync: The visual “rhythm” of the ceiling lights matches the acoustic “rhythm” of the footsteps. As you move away from the microphone, the sound perfectly maps the visual depth of the corridor; the further you go, the more the building “speaks” back to you through echoes.

Material Composition and Acoustic Impact

In the HPT building, you are surrounded by materials with low absorption coefficients, meaning they reflect rather than dissipate sound.

Material	Physical Quality	Acoustic Function	Effect on “Feel”
Exposed Grey Concrete	High mass, dense, smooth	Pure Reflector: Bounces mid-to-high frequencies with almost no energy loss.	Creates the “sharpness” and coldness of the space.
White Metal Doors/Panels	Thin, rigid, non-porous	Specular Reflector: Can cause “flutter echoes” where sound pings rapidly between parallel doors.	Makes every movement feel loud and significant; provides the “clack” sound.
Light Granite/Marble Floor	Polished, extremely hard	First Reflection Point: Immediately reflects footstep noise upward.	Makes every movement feel loud and significant; provides the “clack” sound.
Perforated Metal Ceiling	Porous-looking surface	Sound Trap: The only “soft” element; holes allow sound to enter and be absorbed by insulation above.	Prevents the corridor from becoming an unusable “echo chamber.”

Acoustic Analysis

In your recording, the interaction between these materials is clearly audible as you move away from the microphone.

• 0m – 4m (The Direct Zone): The claps are crisp and dry. Because you are close to the hard granite floor and concrete walls, the Initial Time Delay Gap (the time between the clap and its first reflection) is very short. This feels intimate but “hard”.
• 6m – 8m (The Reverberant Zone): As the distance increases, the reverberation tail grows. You can hear the sound “washing” back from the far end of the corridor. This is the concrete walls and metal doors acting as a giant resonator.
• 10m (The Decay): The sound of the clap takes over a second to fully disappear. This long reverberation time is what gives the space its “monumental” or clinical feel.

Synthesis: How the Materials Shape the Feeling

The combination of these materials creates an “Acoustic Mirror” effect.

Visual-Acoustic Harmony: The white and grey palette looks “clean,” and the acoustics match this—the sound is “clean” (not muddy) because the perforated ceiling is successfully removing the low-frequency “boom”.

Clinical Precision: The lack of soft materials (carpets, curtains) means that every sound is high-fidelity. In a university setting, this feels academic and serious, but also somewhat exposed.

Subterranean Weight: In the HPF stairs, the board-marked concrete has a rougher texture than the HPT walls. This texture scatters (diffuses) sound slightly more, making the echo feel “grainy” rather than “ringing”.

---

SPACE 2

HPF – Parking Staircase – ETH Hönggerberg

The HPF building at ETH Hönggerberg features a transition space that is much more raw and compressed than the HPT corridor. This staircase leading to the “Eingang P1 Sektor C/B3” acts as a vertical transition between the subterranean levels and the open sky.

Volumetric Description

The volume is defined by intense verticality and extreme enclosure.

• Geometry: The space is a narrow, rectangular shaft. Unlike the expansive horizontal perspective of the HPT corridor, the HPF staircase focuses the eye on a single upward point.
• Materiality: This is a pure expression of Brutalist architecture. The walls are board-marked concrete, showing the rough texture of the wooden formwork used to cast them. The presence of moss and weathering on the steps suggests a space that is semi-exposed to the elements.
• Light and Shadow: The volume is sculpted by light. From below, the deep shadows of the concrete shaft contrast sharply with the bright “skywell” effect at the top. From above, the artificial light emphasizes the narrowness of the descent into the building.

Acoustic Analysis

The acoustic profile of the HPF staircase is “shorter” and more erratic than the HPT corridor due to the changing overhead enclosure.

Distance	Acoustic Observation
0m – 2m	The voice and claps are very “tight.” Because the walls are so close together, the initial reflections are almost instantaneous, creating a boxy, resonant quality.
4m – 6m	As the speaker moves up the stairs, the acoustics begin to “open up.” The sound starts to escape into the open air above, reducing the overall reverberation time compared to the enclosed corridor.
8m – 10m	The recording captures the sound of the speaker reaching the top and walking on the surface. The claps lose their “room” character and become much drier as the sound energy dissipates into the outdoor environment.

How the Space Feels

While the HPT corridor felt clinical and infinite, the HPF staircase feels primordial and transitional.

• Atmosphere: There is a sense of “emergence.” Moving from the dark, textured concrete toward the blue sky creates a powerful psychological shift from confinement to freedom.
• Tactile Quality: The rough, board-marked concrete invites a sense of touch that the smooth panels of the HPT building did not. It feels heavy, permanent, and protective.
• The “Ascent”: Acoustically and visually, the experience is one of shedding weight. The sound transitions from the heavy, echoing “weight” of the concrete shaft to the light, open silence of the outdoors.

Material Composition and Acoustic Impact

In this staircase, the materiality shifts from the smooth, “finished” surfaces of the HPT building to a more rugged, industrial expression.

Material	Physical Quality	Acoustic Function	Effect on “Feel”
Board-Marked Concrete	Rough, textured, high mass	Diffusive Reflector: The wood-grain texture scatters sound waves.	Softens the “harshness” of the echo, making it feel more organic and less “metallic” than smooth concrete.
Moss/Organic Growth	Soft, porous, damp	Micro-Absorber: Found on the lower steps; it absorbs a tiny fraction of high-frequency sound.	Adds a sense of age and “dampness” to the acoustics, grounding the space in the earth.
Narrow Concrete Shaft	Parallel, close-proximity walls	Resonant Chamber: The tight distance (approx. 1.2m–1.5m) causes sound to bounce rapidly.	Creates a “boxy” or “hollow” sound; you feel physically enclosed by the noise.
Open Sky (The Ceiling)	Total void	The Ultimate Sound Sink: Sound waves that travel upward never return.	Prevents the build-up of massive reverberation; the sound “escapes” rather than lingering.

Acoustic Analysis

The audio reveals a very different “decay” pattern compared to the HPT corridor:

• 0m – 2m (The Enclosed Start): The clap is extremely loud and immediate. Because the walls are so close, the reflections hit your ears almost instantly, creating a “slap-back” echo. It feels like the building is “shouting” back at you from a very close distance.
• 4m – 6m (The Transition): As you move up, you can hear the background noise of the outdoor environment (wind/ambient campus hum) starting to blend with the footsteps. The concrete walls still provide a strong resonance, but the “weight” of the sound begins to lift.
• 8m (The Exit): When you reach the top, the acoustic profile changes completely. The claps become much “drier.” Without a ceiling to reflect the sound back down, the energy dissipates into the open air. Your footsteps transition from a hollow “thud” on the stairs to a flatter sound on the upper pavement.

Synthesis: How the Materials Shape the Feeling

The materiality and acoustics work together to create a powerful psychological journey:

Tactile Brutalism: The rough texture of the board-marked concrete invites a sense of touch that smooth metal doesn’t. You can “hear” the roughness of the walls in the way the sound reflects—it’s less predictable and more “alive.”

Atmosphere of Protection: The heavy, textured concrete walls make the lower part of the stairs feel like a bunker or a canyon. It feels safe but compressed.

Sense of Emergence: Acoustically, the “opening” of the sound as you reach the top mimics the visual “opening” of the sky. The reduction in reverberation signals to your brain that you are moving from a restricted, interior world into a free, exterior one.

---

SPACE 3

HPT – Ground Floor Volume – ETH Hönggerberg

The entrance lobby of the HPT building at ETH Hönggerberg functions as a monumental civic volume, contrasting the narrow verticality of the HPF stairs and the clinical rhythm of the ground floor corridors.

Volumetric Description

The space is a high-ceilinged, expansive hall that emphasizes transparency and monumental scale.

• Geometry: The lobby is defined by its wide, open floor plan and significant vertical height, particularly visible near the glass curtain wall. A strong central axis is created by a white terrazzo path that bisects the darker stone flooring, drawing the eye toward the primary entrance doors marked “C”.
• Materiality: The architectural language relies on raw, exposed concrete beams and columns with visible board markings. This is balanced by a massive, colorful mural that spans a significant portion of the wall, introducing a humanistic and artistic layer to the otherwise industrial materials.
• Transparency: One entire side of the volume is composed of a multi-story glass facade with dark framing, which visually dissolves the boundary between the interior hall and the exterior campus.

Acoustic Analysis

The acoustic signature of this lobby is much more complex and “live” than the previous spaces due to its sheer volume and the variety of its surface finishes.

Distance	Acoustic Observation
0m – 2m	The voice is clear, but already carries a distinct “hall” resonance. The hard concrete and stone surfaces reflect sound immediately, creating a bright, energetic acoustic profile.
4m – 6m	At this distance, the reverberant tail of the claps becomes significant. The sound energy bounces off the distant glass facade and the high ceiling, creating a wash of sound that lingers longer than in the narrower corridors.
8m – 10m	The recording captures the sound of the speaker reaching the top and wThe space feels its most vast. The speaker’s voice begins to lose directionality as the reflections from the multi-story glass wall and the mural wall converge, creating a rich, choral-like echo typical of large civic lobbies.

How the Space Feels

The HPT lobby feels public, grand, and intellectually vibrant.

• Atmosphere: Unlike the private, quiet feel of the lab corridors, this space is designed for gathering and transition. It feels like a “hub” where the structural weight of the concrete meets the lightness of the glass.
• Visual-Spatial Impact: The presence of the mural provides a focal point that scales the monumental volume down to a human level, while the high ceilings and glass walls create a sense of openness and possibility.
• The Transition: Moving from the outdoor campus through the glass doors into this hall provides a sense of arrival. The transition from the “outdoor” acoustic to this large, indoor “chamber” acoustic reinforces the significance of entering a major academic institution.

Material Composition and Acoustic Impact

The lobby’s materials create a high-energy, reflective environment that emphasizes the building’s grand scale.

Material	Physical Quality	Acoustic Function	Effect on “Feel”
White Painted Beams & Columns	High density, smooth finish	Hard Reflector: Bounces sound with high clarity and minimal loss.	Contributes to the “bright” and “sharp” auditory character of the hall.
Exposed Concrete Ceiling	Raw, heavy, rigid	Sound Mirror: Reflects sound waves back down to the floor, extending reverberation.	Makes the verticality of the space audible; voices “float” in the upper volume.
Glass Facade (Metal Frame)	Hard, non-porous, lightweight	Specular Reflector: Provides a massive surface for “slap-back” echoes.	Creates a visual connection to the outside while keeping the sound energy trapped inside.
Large-Scale Mural	Pigmented layer on flat wall	Decorative Reflector: While colorful, it remains a hard surface that reflects sound.	Acts as a visual focal point in an otherwise clinical acoustic landscape.
Floor Voids (on sides)	Open vertical shafts	Acoustic Channels: Allows sound to travel between floors.	Dissolves the sense of a single floor; you hear the “hum” of the building’s other levels.

Acoustic Analysis

The recording captures a space that is significantly more “live” than the previous locations.

• 0m – 2m (Immediate Presence): Even at close range, the voice has a distinct “hollow” quality. The reflections from the high concrete ceiling and nearby painted columns create an immediate sense of the lobby’s volume.
• 4m – 6m (Reverberant Build-up): The claps trigger a long, shimmering reverberation tail. Because the glass facade and mural walls are far apart, there is a clear time delay between the initial sound and the returning echoes.
• The “Sky” Effect: Because of the side voids and high ceiling, the sound feels like it is escaping upward, creating a sense of “airiness” that was missing in the ground floor corridor.

Synthesis: How the Materials Shape the Feeling

The HPT Lobby is designed to feel transparent, grand, and intellectually active.

Atmosphere of Importance: The monumental scale of the concrete beams and the “live” acoustics suggest a place of gathering and formal arrival. Every sound feels like it belongs to a larger public dialogue.

Visual-Auditory Contrast: While the glass facade makes you feel like you are almost “outside,” the acoustics—the heavy echoes and the resonance of the stone floor—remind you that you are firmly within a massive, permanent structure.

The Art of Structure: The colorful mural and painted beams humanize the “Brutalist” weight of the exposed concrete. Acoustically, this means the space feels slightly warmer and more inviting than the clinical laboratory halls.