Project no2 (Derby University)
The Brief
A local council wishes – in conjunction with a regional arts body – to build a multipurpose venue that will act as a centre of excellence for a broad range of music and entertainment within the city and the wider area.
The venue will act as a performance centre for the city’s youth orchestra and will provide a home for the East Midlands Sinfonia orchestra, a professional orchestra dedicated to making live orchestral music available to a broad section of the community.
The council recognises that the venue is unlikely to be commercially viable if it relies solely on revenue from classical events. Therefore, the design and infrastructure must ensure that a wide range of events can take place. These may include, but are not restricted to:
Amplified popular music, World music
Classical recitals and performances, Choral music
Music tuition for youth orchestras, Dance
Theatre, Conferences, Sports events (e.g. snooker), Exhibitions
Modelling reverberation time
Reverberation is the persistence of sound in a particular space after the original sound is removed. When sound is produced in a space, a large number of echoes build up and then slowly decay as the sound is absorbed by the walls and air, creating reverberation, or reverb.Reverberation time is the time required for a sound in a room to decay by 60 db (called RT60) and defined for wide band signals.
When talking about the decay of an individual frequency, the term decay time is used. The optimum reverberation time auditorium or room of course depends upon its intended use. Around 2 seconds is desirable for a medium-sized, general purpose auditorium that is to be used for both speech and music. A classroom should be much shorter, less than a second. And a recording studio should minimize reverberation time in most cases for clarity of recording.
The reverberation time is strongly influenced by the absorption coefficients of the surfaces as suggested in the illustration, but it also depends upon the volume of the room as shown in the Sabine formula.
[Image:Site Analysis & Green spaces.Derby].
V: volume of enclosure
A: effective absorbing area
A=ΣaiSi
A=a1S1+a2S2+a3S3+…
And a is the absorption coefficient associated with a given area S.
W=22m, L=50m, H=17.5m (auditorium)
V=W*L*H V=14300m H=13m(4,5m closed space with clouds)
S1=L*H=650m2 S2=W*H=286m2
F (floor) =50*22=1100m2 C (ceiling) =50*22=1100m2
A=S1+S2+F+C
125 Hz: A=1164.28m2
250 Hz: A=1655.72m2
500 Hz: A=1345.72m2
1k: A=1242.72m2
2k: A=1378.4m2
4k: A=932.6m2
RT60=0.161V/A 125 Hz: T=1.97 sec.
250 Hz: T=1.39 sec.
500 Hz: T=1.71 sec.
1k: T=1.85sec.
2k: T=1.67 sec.
4k: T=2.46 sec.
