the acoustical design and measures of mixing studio of emei film studio in sichuan

Technical Note

The acoustical design and measures of mixingstudio of Emei ®lm studio in Sichuan

Chen YarmunDepartment of Architecture, Chongqing Jianzhu University, PO Box 400045, People's Republic of China

Received 18 April 1997; received in revised form 22 April 1998; accepted 8 July 1998

Abstract

The mixing studio of Emei ®lm studio is a ®lm sound studio which includes many functions(i.e. mixing recorded sound, dubbing foreign ®lms into Chinese, recording stereo music

etc.).This paper presents the acoustical design and measuring results of the studio of music,which is compatible with speech, the stereo control room and the soloists room. # 1998Elsevier Science Ltd. All rights reserved.

Keywords: Mixing studio; Reverberation time; Noise reduction; Background noise level.

1. Introduction

The new studio is located in the western part of the Emei ®lm studio. The studio isclose to the record works and the existing studio. The front road is a walk road forbicycles. The outdoor noise is mainly from the air conditioning machine room,which has an insulating envelope structure. The new studios stand side by side fromthe existing recording works. A corridor is a width of 2.4m and links the twobuildings from the front. It is an acoustical barrier for the buildings. Fig. 1 is a planof the buildings.The new building is 831m2 which includes the mixing studio, the control room,

the soloists room, the tape recorder room, the photographic sound recorder room,the magnetic sound recorder room, the projection room, a rest room for performersand the o�ce etc. Fig. 2 is a ¯oor plan of new building.

2. Acoustical design

2.1. The acoustical design of the room

2.1.1. The mixing studio (compatible with the announcer's studio)

The reverberation time 0.42 s is used for the mixing studio of the Emei ®lm studio.This is a powerful absorption studio having better directional characteristics. The

Applied Acoustics 57 (1999) 179±191

0003-682X/99/$Ðsee front matter # 1998 Elsevier Science Ltd. All rights reserved.

PII: S0003-682X(98)00041-3

Fig. 1. The plan view of new building,(1) new studio, (2) built studio, (3) recording works, (4) air con-

ditioning machine room.

Fig. 2. The ¯oor plan of new studio, (1) mixing studio, (2) control room, (3) soloist's room, (4) tape

recorder room,(5) the air conditioning machine room for new studio, (6) performers rest room.

180 C. Yarmun/Applied Acoustics 57 (1999) 179±191

volume of the mixing studio is 1005M3, The reverberation time is 0.42 s, so that themean absorption coe�cient of the room is �=0.427. The room absorption isA=295.3M2. The absorption materials are decorated equally and di�used surfacesare shaped fully. As a result, the sound ®eld is uniform throughout the mixingstudio. Table 1 lists the acoustical treatment of the room.The acoustical defects of the echo and ¯utter echo etc. must not be created by

re¯ections from the room surface. Fig. 3 is the plan of the mixing studio. Fig. 4 is thedi�usion cones on-arrangement at the side wall.

2.1.2. The control roomThe control room is a monitor room of stereo items. The initial time delay gaps of

re¯ected sound in the monitor room are longer than the initial time delay gaps ofre¯ection sound in the studio. [1] It must be considered fully in the design process.The reverberation time in the control room must be shorter than that of the studioso that the reproduced sound transmitted from the studio to the control room canbe heard. [1] The sensation of direction, reverberation and space in the studio can berecorded fully.A method by which longer initial time delay gaps are achieved in the control room

is shown in Fig. 5. The rear walls and the rear ceilings farther from the soundsources are used as re¯ection surfaces, so that long delay re¯ection sound isachieved. The walls and ceilings nearer to sound sources are treated with powerfulabsorption materials so that shorter delay re¯ection sound is achieved. This is thedesign method of the ``Live End±Dead End''. The above-mentioned objectives canbe achieved only when the length of the control room is not less than 7.5m. Theroom shape and the acoustical treatment must be symmetrical with the center axisfor the stereo control room, so that a real feeling of direction can be achieved.The reverberation time objective is 0.38 s for this control room. The volume of the

room is 120.8M3 so that the mean absorption coe�cient of the room is �=0.284.The room absorption is A=43.5M2. The sound source height is 2m. The treatmentfor re¯ection or absorption for the walls and ceilings is shown in Fig. 5. The

Table 1

The acoustical decoration of the mixing studio (compatible with announce studio)

Items Formation and decoration

Ceiling Six cones of 1700 x 1000, 1700 x 2280, 3800 x 2280 of which the heights are 40, 60, 80 cm

respectively, faced with plastic net plate of 20 x 20, ®lled with 100mm glass wool

of 20 kg/m3

Side wall Folded wall faced with plastic net plate of 20�20 ®lled with glass wool and 60 cones

of 1050�1050 faced the steel plate net of 15 x 15 with 40mm plaster are alternated

Rear wall Folded walls faced with 5mm perforated plywood ®lled with 100mm glass wool

Front wall Wall faced with plastic net plate and ®lled with 100 mm glass wool

Skirting wall 5mm plywood ®lled with 100mm glass wool

Floor Wood ¯oor

C. Yarmun/Applied Acoustics 57 (1999) 179±191 181

absorption surface is faced with a plastic net and ®lled with 100mm glass wool. There¯ection surface is faced with a steel net made with 40mm plaster. The skirting wallis 80 cm high faced 5mm plywood ®lled with 100mm glass wool. The air space is150mm deep.The left and right channel monitor speakers must be isolated with resilient pads

from the structure, in case the solid borne sound is transmitted to the recorder. Thestereo reproduction image will be destroyed because the transmission speed of thesolid borne sound is faster than that of the air borne sound.As many normal mods as possible must be obtained within the frequencies below

200Hz for the monitor room. There are preferred ratios of room dimensions, thegoal of which is to distribute the modal frequencies in an optimum manner. Thecoincident frequencies called ``degeneracies'' must be decreased as fully as possible.

Fig. 3. The plan of the mixing studio.

Fig. 4. The di�usion cones arrangement on the side wall of the mixing studio.


2.1.3. Soloist's roomSolo music is recorded in the soloist's room. The area of room is 20M2, 0.3 s

reverberation time is designed. The room volume is 49M3 so that the meanabsorption coe�cient is �=0.238. The room absorption is A=18.7M2. The left andright wall and the front and rear wall must be treated irregularly. The ratios of theroom dimensions are not integers, so that both as many normal modal frequenciesand as good di�usion as possible in the room are achieved. The fold-out walls of thesoloist's room are shown in Fig. 6

2.2. Sound insulation and vibration isolation

The objective is to avoid disturbing sound travelling between rooms. Such noisesinclude airborne sound and solid borne sound and air ¯ow noise transmitted by theventilating system.

Fig. 5. The longer initial time delay gaps are achieved in the control room. (a) The section view of sound

re¯ection and the arrangement of the absorption surface and the re¯ection surface. (b) The plan view of

sound re¯ection and the arrangement of absorption and re¯ection.


The noise transmitted from foyer and staircases is insulated by the sound lockformed by two sound-insulating doors, The major noise source outside the mixingstudio is ventilator noise. The room installed ventilators must be separated fullyfrom the mixing studio. Between the studio and the ventilator room are insulatedwalls, three layers consisting of two air layers. The inside and outside of the mixingstudio are insulated by a double wall. The studio and control room or studio andsoloist's room are insulated from one another by the observation windows formedwith 6, 8 and 12mm plate glass.Fig. 7 shows the insulation construction of ceiling and roof. The insulation ceilings

are formed using steel nets with 40mm plaster supported resiliently under the roofconstruction. The construction of the resilient supports is that the � 12 hanger steelbars are welded on the No.16 channel beams supported on neoprene isolation pads.The ¯oor is a wood ¯oating ¯oor. The construction of the ¯oating ¯oor is shown

in Fig. 8.Four conditioning systems (K-1, K-2, K-3, K-4) are used in the studio, K-1 and

K-2 systems are used in the mixing studio, K-1 system is used in the control room

Fig. 6. The fold-out walls of the soloist's room.

Fig. 7. The construction of the resilient support ceiling in the mixing studio.


and the soloist's room and K-4 system is used in the projection room and the ®lmediting room. Governors are used in the lower noise blowers so that air¯ow noise isreduced. The silencers are inserted within the tube systems. The air conditioningcases in the machine room are put on spring dampers and the water pumps are puton isolation bases. Pipework connected to the air conditioning plant and the waterpipe connected to pumps are separated by the ¯exible collars. The ¯exible collars areinserted at places in the wall where air ducts and line pipes pass through.

3. The acoustical measurement

The measurement items include the reverberation time, tile airborne sound insu-lation, the impact sound isolation, the background noise level, the acousticalresponse and the transient response. The respective descriptions are detailed.

3.1. The reverberation time

3.1.1. The mixing studioThe volume of the mixing studio is V=10.68m(W) x 15.20m(L) x

6.20m(H)=1005m3, The surface area of the room is 691.3m2, nine measured pointsin the room are distributed uniformly. The heights of measured points (the Micheights) are 1.2 and 2.4m, respectively. Table 2 is the measured results of T60. It canbe seen from the measured results that the reverberation is distributed equally in themixing studio. A ¯at frequency characteristic of the reverberation time is achieved.

3.1.2. The control roomThe volume of the control room is V=7.36m(L) x 5.13(W) x 3.20(H)=120.8m3.

The total surface area of the room is S=153.3m2. The reverberation time at two

Fig. 8. The construction of the ¯oating ¯oor.


points in the room is measured, the height of the measured points is 1.2m.Table 3shows the measured results. It can be seen that the equalization of the frequencycharacteristic of the reverberation time changes within � 5%.

3.1.3. The soloist's roomThe volume of the soloist's room is V=46m3, The total surface area of the room

is 78m2. The height of the measuring points is 1.2m.Table 4 the measured results.

3.2. The insulation of noise

3.2.1. The measurement of airborne sound insulationThe air-borne sound insulation of Nos.3, 4 and 5 sound insulating doors and the

observation windows are measured, respectively. Nos.1, 2 and 3 sound insulatingdoors are double leaf door of 2100mm(H)X 1500mm(W), Nos.4 and 5 sound insu-lating doors are single leaf doors. Tables 5±7 show the respective measured results ofNos.3, 4 and 5 sound insulating doors in situ. Tables 8 and 9 are measured results ofthe observation windows in situ. The position of the sound insulating doors and theobservance windows are shown in Fig. 9.

Table 2

The mixing studio T60�S�The height of measured Frequency (Hz)

points(m)80 125 250 500 1000 2000 4000 6300 8000

1.2 (m) 0.40 0.40 0.41 0.42 0.43 0.44 0.44 0.44 0.44

(MSD) � 0.02 0.018 0.018 0.01 0.01 0.015 0.01 0.01 0.009

2.4 (m) 0.41 0.40 0.40 0.41 0.41 0.42 0.43 0.43 0.43

(MSM) � 0.018 0.02 0.008 0.008 0.01 0.01 0.01 0.01 0.01

Table 3

The control room T60 (S)

Frequency (Hz)

The measured points80 125 250 500 1000 2000 4000 6300 8000

1 0.35 0.35 0.35 0.37 0.37 0.38 0.37 0.36 0.35

2 0.35 0.35 0.38 0.38 0.39 0.40 0.39 0.38 0.37

Average 0.35 0.35 0.36 0.37 0.38 0.39 0.38 0.37 0.36

Table 4

The soloist's room T60 (s)

The heights of the Frequency (Hz)

measured points80 125 500 1000 2000 4000 6300 8000

1.2m 0.41 0.36 0.37 0.38 0.36 0.37 0.40 0.40 0.40


3.2.2. The measurement of impact sound isolationThe standard impact machine is placed on the ¯oor of the projection room where

the projector will be ®xed. The impact sound level was measured in the mixing stu-dio, control room and soloist's room and in the receiving room,and was normalizedto a reference absorption to yield the normalized impact sound level LN given inTable 10.

Table 5

The sound level reduction of door No.3 in the control room

Frequency (Hz)

Sound level (dB)125 250 500 1000 2000 A C

Sound source room 95 95 95 95 93 99 102

Receiving room 63 67 64 62 57 67 76

Sound level reduction (dB) 32 28 31 33 36 32 26

Table 6


Frequency (Hz)

Sound level (dB)63 125 250 500 1000 2000 4000 8000 A C

Sound source room 96 95 95 95 95 93 90 83 99 102

Receiving room 78 70 59 57 56 53 51 43 61 78

Sound level reduction (dB) 18 25 36 38 39 40 39 40 38 23

Table 7


Frequency (Hz)

Sound level (dB)63 125 250 500 1000 2000 4000 8000 A C


Receiving room 65 62 58 55 62 55 56 54 65 69

Sound level reduction (dB) 31 33 37 36 33 38 34 28 34 33

Table 8

The sound level reduction of the observation window in the control room

Frequency (Hz)

Sound level (dB)63 125 250 500 1000 2000 4000 8000 A C

Sound source room 102 100 99 99 99 96 103 107

Receiving room 71 62 52 40 48 43 52 72

Sound level reduction(dB) 31 38 47 59 51 53 51 35

Sound insulation index Ia=54dB.


3.3. The background noise level in rooms

After the air conditioning system is run in the measured noise level in di�erentrooms is given in Table 11. Before the air condition equipment is run, the measurednoise level in di�erent rooms is given in Table 12.

Table 10

The normalized impact sound level of rooms

Normalized impact sound Frequency(Hz)

level (dB)125 250 500 1000 2000 4000 8000

Mixing studio 38 40 31 24 13 13 13

Control room 55 59 56 45 31 18 15

Soloist's room 54 57 51 42 26 14 13

Table 9

The sound level reduction of the observation window in the soloist's room

Frequency (Hz)

Sound level (dB)63 125 250 500 1000 2000 4000 8000 A C


Receiving room 58 58 44 43 34 29 15 12 46 76

Sound level reduct 47 40 54 51 57 63 74 69 52 31

Sound insulation index Ii=57dB.

Fig. 9. The distribution of sound insulation doors, observation windows and the measured points of

impact sound.


3.4. The measurements of the acoustical property of the control room

Echograms were obtained so that the initial delay gaps of the re¯ected sound inthe control room could be assessed; the acoustical response of the left or right soundchannels at the monitor point are measured so that the directivity symmetry ofstereo in the control room could be examined.The echogram at the center in the mixing studio is shown in Fig. 10. It was

observed that the initial time delay gap of re¯ected sound in the mixing studio isapproximately 17ms. The echograms of the right and left channels in the controlroom are shown in Figs. 11 and 12. It was observed that the initial time delay gapsof the re¯ected sound were approximately 25 and 15ms respectively.

Table 12

The background noise level (dB) (air condition machines stop)

Frequency (Hz)

Rooms80 125 250 500 1000 2000 4000 8000 A

Mixing studio 21 18 9 7 6 8 8 8 17

Soloist's room 24 20 10 9 7 8 8 8 19

Table 11

The background noise level (dB) (air condition machines are running)

Frequency (HZ)

Rooms80 125 250 500 1000 2000 4000 8000 A

Mixing studio 40 35 35 34 36 34 17 12 38

Control room 41 34 24 15 9 10 10 11

Soloist's room 35 38 21 13 8 9 10 11 23

Fig. 10. The echogram in the mixing studio. (Frequency 2000Hz, every one of time marker is 15ms).


Fig. 12. The echogram of the left channel in the control room. (Frequency 2000Hz, every one of time

marker is 15ms).

Fig. 13. The spectrums of the left and right channels on the monitor point of the control room.

Fig. 11. The echogram of the right channel in the control room. (Frequency 2000Hz, every one of time

marker is 15ms.


The spectrums of the left and right channels are shown in Fig. 13. It was notedthat the left and right show no di�erence near the middle and high frequencyregions, The directivity of the sound sources are not dampened by the control room.

4. Discussion and conclusions

(a) After a long usage of the built mixing studio of Emei Film Studio, a goodacoustical quality is proven. It has one of the best acoustical qualities of stu-dios in China. The acoustical design of this studio was rigorous. It is not easyfor a ¯at frequency characteristic to be achieved. The re¯ected sound is dif-fused fully by about 60 solid cones distributed uniformly on the wall surface.

(b) The measured reverberation time T60 in the mixing studio is 0.41 s; T60 of thecontrol room is 0.38 s. The demand of acoustical design is met whereby T60 ofthe control room is shorter than T60 of the mixing studio.

(c) The mean transmission loss door No.1, door 2 or door 3 is about 32 dB. Thereduction of the sound lock in the mixing studio is satisfactory. The meantransmission loss of door No.4 or 5 is approximately 34 dB, although thereductions of the insulation doors are su�cient. The mean transmission lossesof the observance windows are higher than 54 dB. and good insulation isprovided.

(d) The impact isolation index of the mixing studio is Ii=32. Ii of the controlroom is 52. Ii of the soloist's room is 49. It is evident that the isolating impactsound insulation of the ¯oating ¯oor in the projection Referoom is excellent

(e) After operation of the air conditioning plant, the background noise level waslower than NR15 in the control room and in the soloist's room. In the mixingstudio, the background noise level is slightly higher than NR25 in the middleand high frequency regions. When the mixing studio is used, one of the twoair conditioning machines will be soon ®nished o� or the running speed ofthe machines will be decreased. Under these conditions the background noiselevel will be decreased to NR20 or lower.

Reference

[1] Alton. E.F. Acoustic techniques for home and studio. USA: TAB Books Inc., 1984: 233±5.


the acoustical design and measures of mixing studio of emei film studio in sichuan

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