task6

Purpose

In this lab task we will design a recording studio control room. By using a 1:10 scale model, we will optimize both the low and high frequency range and temporal aspects of a 6 x 3.8 x 2.4 m room as well as design a neutral sounding monitoring and mixing environment.

Introduction

In a recording studio one can find several rooms where music is played and recorded. A studio, a control room (such as the one we are studying in this lab), a machine room, an office and a kind of green room for the musicians are usually found in those recording studio. There are several basic acoustic factors which must be incorporated in the recording studio such as quietness, the noise isolation from an area to another, freedom from acoustical defects such as flutter, adequate absorption and diffusion...

All those characteristics will differ from one room to another and are sometimes tricky to deal with. But here our main room of interest is the control room.

The control room is a working place used for the mixing of sounds thanks to a recording and electronic processing equipment (the main one is the mixing consol). Such a room is usually small ( ours is a bit less than 55 cu m ) and has to be well designed acoustically in order to have good recording. Such an environment requires low reverberation time. Typically 0.7s is desired over the entire audio frequency range

Two frequency domains can be seperated in order to define a good design for a small control room. We divided into two frequency ranges: Low frequency from 20 to 100 Hz and high frequency from 100 to 2000 Hz.

Since we investigate a 1:10 model of the control room, the frequency ranges used in the software were 200 to 1000 Hz for the low frequency range and 1000 to 20000 Hz for the high frequency range.

In the two subsections below, are described the different methods to improve a simple shaped control room; one can find how we performed the measurement and what the different conclusions are regarding the different methods we used.

The summary section sums up the results and gives a kind of conclusion on what would be the best way to improve such a control room.

Tasks

1) Low frequency range.

2) High frequency range / temporal distribution.

Summary

The first thing to say is that we were the first group measuring and it appeared that all the other groups had problems with the software. Regarding the presentation on friday it seems like our results are a bit different than theirs. A non-identified problem of the software can thus be an explaination for those differences. Still hoping our results are reliable we can sum up and conclude on what we think is important.

The improvement of the frequency response in low frequency ranges is mostly a question of flattening and attenuating the first modes. The latter can be achieved by using Helmholtz resonators adjusted to the modal frequencies of the room. The flattening is most easily done by putting porous absorbers in the room. In our case we used small absorbing patches and corner wedges. The result of comparisons between resonators, patches and corner wedges shows that the best flattening is achieved by using the corner wedges. The absorbing patches nearly have no influence on the frequency response, so do the resonators.

After having detected where the first reflection came from, we were able to confirm the efficiency of the absorbers and the diffusers on the flutter echoes. It turned out that a good compromise would be to use both correctly placed in the room (LEDE design). We would suggest to use the LEDE method in order to design a good control room. The first motivation for that choice is the fact that the response of the room looks way better with this layout than the "naked" room. The second choice is that, while comparing to the NE method, it must be much more comfortable to work and listen in a LEDE room than a NE room, moreover the NE room is not really what a typical living room is looks like.

Improvements

If one wants to improve the room further more, one can think about another way to shape the room. One should have a symmetrical layout but without parallel walls, that would avoid flutter echo effects since the sound would not go back and forth between two parallel walls. For the same reason, the ceiling of a control room is not parallel to the floor, but is usually lower near the front wall, and higher towards the back wall; wide-band absorbers should be placed on the ceiling. One could also be interested in moving the rear wall more than 3 meter away from the missing position in order to have a long enough time gap between the reflections coming from this wall and the direct sound. This distance should not be too important since one does not want to perceive echoes.