Storage Room:

Claps:

The storage room is about 3×3 meters. The walls, ceiling and floor are all made in a concrete finish. This room can also function as a bunker, this is why ti has a ventilation system. It also has a small window in the center of a wall. During the day you sometimes can hear birds chirping and other stuff happening in the outside world. In the evening when the world is quieter you can hear the piping of the building, probably the water pipes. Even though the reverb decayed fast, I was very surprised that the room sounds bigger than it is. I think because of the concrete walls the reverb was rather high for a such small room. I also found it interesting that the different distances didn’t sound that much different. I think it’s because in this small room the early reflection of the reverb gets fast to the microphone and because of the concrete walls they bounce alot. I also tried to get a flatter echo but I think because of the shelfs in this room It didn’t work. It would be interesting to remove the shelfs to try to get a flatter echo.

Surfaces:

There are no clearly identifiable acoustic absorbers in this space. The room is dominated mainly by hard and smooth surfaces, which means that most of the sound is reflected rather than absorbed. One possible exception might be the empty cardboard boxes on the top shelf. Because cardboard is lighter and less rigid than the surrounding materials, and because the boxes contain air, they could provide a small amount of sound absorption, although probably only to a limited extent and more in the higher frequency spectrum. The wooden shelves themselves are also unlikely to absorb much sound. Instead, due to their uneven arrangement, they probably scatter the sound and thus act as diffusers.

Passage HPF to HPT

This space is vis-a-vis of the HIT building on top of the garage. It’s about 5 meters wide and 20 meters long. The space is open on the two longer sides. One of the 2 open side has a lot of foliage.
Sounds which get produced outside of this space don’t get much acoustic characteristics when entering the space. I think it’s because of the sound waves not hitting any surfaces, namely ceiling or floor. But the sounds generated from within the space do get some acoustics. The first 2 meters you almost hear no reverberation but starting from 2 meters you can start to hear the reverb quite good. The reverb “forms” a flutter echo. I guess most of the reverb comes from the hard ceiling and the entrances on either side. I think it’s a very interesting intersection between indoor and outdoor. Ignoring sourounding sounds I probably couldn’t assign these spaces with a 100% accuracy to indoor or outdoor. I find it fascinating where the threshold lies between people perceive a recording as indoors or outdoors.

Surfaces:

Interesting in this space is that 2 sides are open. The fully open side to the right functions as an infinite absorber (sky). On the lower third of this open right side there is a glass fence. iThis fairly hard Material(Glass) probably reflects the incoming sound waves quite hard. On the open left side there are growing trees and bushes. They scatter the sound an act as a diffuser.
The ceiling as well as the floor are made out of fairly hard materials. and at the ends are glass doors. these hard surfaces reflect the sound also pretty good. This is probably the reason for the flutter echo.

Assignment 3

Claps:

Audacity:

For this assignment I chose the storage room. I analysed the third last clap because I felt it was the best. I only could get a -30 db reading that was 0.18 seconds. So for the RT60 it’s 2*0.18 =0.36 seconds.

In my Sarooma site I assumed the stuff on the shelf is about 2m^2 of absorption.

Assignment 4

The measurements clearly show that the room has poor speech acoustics. The reverberation time remains consistently high, at around 1.5–1.7 seconds across almost all frequencies. I imagine the room sounds very echoey, and voices tend to overlap, especially when several people are speaking at the same time.

This acoustic behaviour is mainly caused by the room’s material surfaces. The space is dominated by hard, reflective materials: a concrete floor and ceiling, smooth plastered walls, and a large glass façade running along the full length of the room. These surfaces absorb very little sound, so most of the acoustic energy is reflected back into the space.

The other acoustic indicators confirm the same problem. The measured C50 values are negative, meaning that late reflections dominate over early sound energy. This reduces speech clarity. The Speech Transmission Index ranges from 0.51 to 0.55, which corresponds to only fair intelligibility. In practice, this means that speech becomes difficult to understand over distance, and conversations become tiring in group situations.

My proposed new use for the space is a new small atelier/studio room. I classified the studio space as an office (B4) and not as a classroom (B3), since in studios there is a lot of group work and not a single person talking like in school. 

The requirements for offices are: 

Using the numbers V=637, h=4.83 we get a minimum absobtion surface of 119.34 square meters.
The current absorption property of the room is as follow

I decided to use curtains as spacial divider between different groups. I need about 18 meters of curtain. I want to hang it down from about 3 meters. This is a good height because most people are not larger than 3 meters. So a lot of direct sound gets blocked. So the total area is 18*3=54 square meters. Using theses properties for an acoustic curtain:

I decided to go with the Fullness 1.5 values since the curtains act as divider between groups I assume they always stay at Fullness 1.5. For this product there are no absortion coefficiant listed for 8kHz but by comparing different similar products I arrived at a coeficiant around 0.8 s
These are the absorption areas for the curtain:

Now the room still has an issue with frequencies around 63-250 Hz. To control them we can either use a bass traps in the corner, helmholtz resonators, plate absorbers or active basstraps. Since bass traps also affect other frequencies besides the 63-250 band I ignore them for now. And active bass traps seems a bit overkill and require power or can break. So that leaves helmholtz resonators or plate absorbers. I went with a plate absorber since the depth of a helmholtz resonator at these low frequencies are almost double. The absorbation range is also a bit wider in a plate absorber.
In the end I decided to use this absorber:

These are the absorption areas of the plate resonator. I couldn’t find any values for the 8kHz range but since they are probably very low and don’t have a huge impact  we can ignore them. 

So the room still needs a bit of absorption for the high frequency bands.

For this I decided to use the ceiling. I found that felt panels are quite nice for fairly isolated absorption in the higher range. In the end I decided to use following product and directly mount it on the ceiling.

which adds these absorption areas:

In the end the total absorption area is as following

Calculating the reverberation time sabine

Because speech is the primary sound source in a studio, I focused on achieving the required reverberation time in the 500 Hz–4 kHz frequency range. In these bands the room achieves the reverberation time for A3 (Nutzungsart: „Unterricht/Kommunikation bis 1’000 Kubikmeter.)
The room is still a bit lacking in the lower and higher frequency bands. Lower reverberation times could be achieved by increasing the area of felt panels or plate absorbers.