208 Recording Studio Design layer of 60 cm thickness of 40 kg/m 3 mineral wool. The other walls are con- structed as shown in Figure 5.1. The floor is hard and the glass doors are useful for good visibility if the musician is in the room, and not playing via a remote amplifier head. Never- theless the same conditions apply as were discussed about the room shown in Figure 5.19, whereby the directionality of the microphones can be used to avoid picking up any undesirable reflexions. In the cases of bass amplifiers facing the super absorbent wall, the microphone would normally be between the amplifier and the absorber, and so would be shielded from any room effects. When money and space allow, these rooms can prove to be very use- ful adjuncts to a studio. They can also be highly useful where voice-over or dialogue replacement requires a totally dry voice, such as for a scene in a snow-drift, where conditions would tend to be anechoic, and any trace of room ambience on the recording would spoil the effect. The principal difference between the room shown in Figure 6.14 and that of Figure 5.19 is the much greater low frequency absorption of the former room. Obviously, this can only be achieved at the expense of requiring a larger space for the construction. A specialised version of such rooms is the Foley Room. 6.17 Foley rooms Another type of studio room which requires a relatively dead acoustic, and which is important in the film industry, is the Foley room. Named after Jack Foley at Universal Pictures, who was Hollywood's first specialist in this artform, they are used for the recording of minor sound effects such as footsteps, opening and closing doors, jangling keys, hands knocking on windows, and other such sounds which may have been badly captured by the original recording microphones or which may have been lost when ori- ginal dialogue soundtracks have been replaced, such as in foreign language versions. Obviously, when such recordings are re-mixed into the sound- track they must acoustically match the image on the screen. It can be detri- mental to the realism to hear the voices of two men rowing a boat on a lake whilst the splashing of the oars clearly sounds like it has been recorded in a room. Such things may be acceptable in a comedy film but they would greatly affect the credibility of a serious drama. In general, it is better to record the Foley effects in an acoustically dead room, and then use artificial means to match the ambience of the sound to the context of the picture. Figure 6.15 shows a specially designed Foley room which can also be used for the mixing of stems (pre-mixes of effects, music etc.) in 5.1 surround. On the floor can be seen different surfaces ­ wood, stone, carpet, water, metal and gravel ­ for the Foley walkers to synchronise their footsteps to the picture. There are spaces under some of the surfaces to introduce different quantities of damping materials, and the water depth can be varied. The room is usable either with projector and screen or with a video monitor. The construction of the room shown in the figure is generally similar to the principles shown in Figures 5.1, 5.3, 5.4 and 5.5. The front wall needs to be very rigid in order to provide an extended baffle for the loudspeakers, and so cannot be absorbent at lower frequencies. At higher frequencies, the perforated