1 Acoustic Profiles
Room 1: Staircase HIL
Location
The staircase chosen for this assignment is a closed space (with the exception of frame opening on the upper platform) located between floors B and A at the HIL building at ETH Hönggerberg campus.
Recordings
The samples were recorded from a 0m, 2m and `10m distance from the microphone. A sample of voice followed by a hand clap was recorded.
Unique recorded sounds
A person walking by was recorded during the observation time.
Soundscape sketch
Description
A personal interpretation on how the staircase sounds.
The purpose of this room is self explanatory. The spaces it connects are the lowest basement floor A with archives, storage rooms and service rooms together with floor B, where other corridors are connecting workshop rooms and other facilities.
The staircase uses only two types of material. The floor and the ceiling are made of concrete, while the walls are made of concrete blocks. The walls and floors are treated with a paint coat, which even enhances the already sound reflective surfaces. There are no acoustically treated surfaces. The space can be characterized as reverb-y, very live and cavernous.
The recording at 0 meter distance records a very loud and dense voice and clap. They both fill the space with a harsh and relatively long ringing decay of sound. The reverb is extremely boomy, it enhances the low tones in the voice and causes vibrations that resemble a sound produced by high voltage electric cables. At 2 meter distance from the source, the echo starts to interfere with the voice; the clarity of articulation decreases and the overall outcome becomes muddy. At 10 meter distance from the microphone, the sound of the voice shifts from being sharp to very round. At this point, I have a feeling that the secondary sound that is reflected from the walls and horizontal surfaces and travels to the microphone becomes somehow equal or stronger than the sound coming directly from the source. The voice is no longer this sharp and sizzling sound that travels directly through the space. The higher frequencies are less dominant ant the deeper, echoey sound dominates the room.
The recorded foot steps are clearly distinguishable but as they proceed further from the microphone. similarly as the voice, the individual steps become harder to distinguish as the sound almost gets lost in the reverb.
When it comes to perception, the space creates a sense of exposure, non-intimacy and unease. The sounds become over-amplified, the low ceiling causes almost immediate reverb and even slightest knock on the door lingers seconds in the air. One does feel no need to talk as all conversations blur in the room and together with the footsteps, it all turns into a rumble.
The water running through the sewage pipes, located below the ceiling in the adjacent room, behind the close doors, can be heard if the stairwell is in total silence. The sound is, however, very negligible, and the sizzling sound can only be heard when standing right next to the door. Interesting to observe was also the occasional presence of reflected human voices that travelled through the corridor and the opening (on the upper platform) into the stairwell from one or two stories above. Somehow, the claustrophobic room still remained connected with the outside world via these very distant, but not very clear sound reflections.
Looking back at the soundscape plan, I would expect the high-frequency sounds to be present across all distances. However, the truth lies elsewhere and the reflectiveness of the space causes the volume of the stairwell room to be hyped up by the echoes. For the size of the room, the acoustic qualities can be seen as a bit chaotic and one gets immersed in a field of constant sound reflections.
Room 2: Lecture Hall HIL
Location
The lecture hall chosen for this assignment is also located inside the HIL building, on floor F. It is as a fully closed space, with two door openings, one on each side that can be closed.
Recordings
Same as in the staircase, samples were recorded from a 0m, 2m and `10m distance from the microphone. A sample of voice followed by a hand clap was recorded.
Unique recorded sounds
When sitting in silence during the observation time, the integrated ventilation system ducts could be heard. The noise, however, was only coming from the front of the classroom, above the chalkboard. The main inlet and outlet is probably located in the ceiling in this part of the room.
Soundscape sketch
Description
A personal interpretation on how the lecture hall sounds.
The purpose of this space is for holding lectures, exercise classes or presentations. Spoken word is therefore most important when it comes to the acoustic functionality and focus of this room. The layout can be considered as a classic classroom. In the front, the teacher’s table together with chalkboard are located. They are elevated one step from the rest of the classroom, so that the voice can travel better.
Despite the size of the room, the space feels surprisingly dead and together with the bright lighting also slightly sterile. If absolutely silent, a pen dropped on the ground can be heard loudly and clearly without additional echo.
The recordings showcase a drop-off in sound. At 0 meter distance, the voice and clap are incredibly crisp, clear and loud. For the voice, there is almost no reflection, however, since the podium has a linoleum floor (not carpet) the clap produces a slight bouncy, metallic echo. At 2 meters, the voice is still clearly heard, it is still balanced. I would say, it remains with the same characteristics but with lower intensity. The clap echoes much less than when above the microphone at 0 meter distance. At 10 meter distance, the voice again decreases in intensity but it also becomes dull. At this point, the listener can feel a little bit detached from the lecturer, and one must make an effort to stay concentrated at the voice.
Generally, the voice and clap travel through the room very clearly, causing for an alert, somehow harsh, crisp acoustic atmosphere, where it takes only a little effort to change the intensity of one’s voice. The reflective surfaces in the room, such as the walls, chalkboard and large writing tables bounce the high-frequency sounds, which causes the human voice (the speaker) to sound crisp, articulate and not muddy. On the other hand, the whole ceiling, consisting of perforated metal acoustic panels, together with the carpeted floor prevent reverberation, or the reflection of any unwanted talks between the students (listeners) across the room. Due to this acoustic treatment, which prevents echoes around the room, the intensity of the speaker’s voice decreases with the distance from the speaker.
What is important to mention, is the constant humming sound of the ventilation ducts. They can be found in the ceiling in the front of the room, where also the speaker would stand. This subtle sound can be heard across the whole room, resembling a type of white/green noise. The noise from the air rushing through the ducts is, however, not disturbing or distracting but is present across the room.
To conclude, looking back at the soundscape sketch, the louder, higher pitch sounds gathering around the 0m and 2m radius matches very well how the room physically feels. Due to the acoustic ceiling treatment and carpet floor, the sound does not efficiently carry to the back of the room, is does not fill the space evenly, thus the sound is best concentrated next to the source.
