Acoustic design and measurement
A room answers back.
Sound leaves a source, meets six surfaces, and comes back changed. We draw that before anything is built, measure it once it is, and give you the schedule that got you there.
Hall B, recital and rehearsal
Hall B, recital and rehearsal
Length
24 m
Width
14 m
Height
9.4 m
Rake
6 degrees
Platform
5.5 m deep
Volume
3158 m3
The drawing to the side is these six figures and nothing else. Change one and the section changes, the rays land somewhere new, and the number at the foot of the screen moves with them.
Six surfaces, and what each one keeps.
Plaster ceiling
Hard, and doing all the reflecting
336 m2 6% of the absorption
Upholstered seating, occupied
Where two thirds of the sound goes
236 m2 63% of the absorption
Oak platform and aisles
Sprung, so it gives a little back
100 m2 3% of the absorption
Plastered side walls
Splayed 4 degrees to kill the flutter
380 m2 6% of the absorption
Perforated rear panels
Broadband, tuned low, stops the slap
131 m2 22% of the absorption
Glazing to the foyer
The one surface we would remove
71 m2 1% of the absorption
Volume is taken as the plain box, which is how Sabine took it. A shaped ceiling moves reflections around; it does not move the reverberation time much, and pretending otherwise is where most acoustic reports go wrong.
Draw it, build it, then go and listen.
01 Section
One drawing, at scale, with the seating rake and the platform on it. Every argument about a room is really an argument about its section.
02 Schedule
Every surface, its area, and its absorption at six octave bands. This is the deliverable the contractor prices, so it is written to be priced.
03 Prediction
Reverberation by Sabine, early reflections by ray. Both are approximations and we say which is which, rather than dressing a guess as a simulation.
04 Measurement
A balloon, a swept sine, and an omnidirectional microphone at nine seats. The room gets the last word and it usually disagrees by a tenth of a second.
What the room is meant to be for.
| Chamber music | 1.4 to 1.6 s | Occupied, 500 Hz to 1 kHz |
|---|---|---|
| Rehearsal | 1.0 to 1.2 s | Players need to hear each other, not the room |
| Speech and lectures | 0.7 to 0.9 s | Consonants survive or they do not |
| Amplified music | 0.6 to 0.8 s | The system supplies the reverberation |
This room, as scheduled: 1.53 s at 500 Hz, from 332 metric sabins.
Send us the section.
A drawing and a use is enough to start. We will tell you within a week whether the room can do what you want, and what it would cost to make it.
Unit 4, Cooper's Yard Glasgow G1 5RB
Acoustic consultants. Institute of Acoustics, corporate members since 2011.