SMPTE ST 222M-1994 Television - Control and Review Rooms - Monitor System Electroacoustic Response.pdf

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1、SMPTE 222M 94 m 8357403 O003766 729 m SMPTE STANDARD ANSI/SMPTE 222M-1994 Revision of ANSIISMPTE 222M-1987 for Television - Control and Review Rooms - Monitor System Electroacoustic Response 1 Scope 1.1 This standard specifies the method of measurement and characteristics for the monitor chain elect

2、roacoustic response of television control and review rooms with volumes of 150 m3 (5300 ft3) and smaller. It is intended to assist in standardization of reproduction of pro- gram sound in television control and review rooms. 1.2 It does not apply where the recorded sound is intended for reproduction

3、 under theater listen- ing conditions; .e., to motion-picture or public address systems. This standard does not cover equalization standards for other parts of the system, such as fixed or variable equalization applied for noise reduction around tape recorders, or the like. 2 Normative reference The

4、 following standard contains provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate th

5、e possibility of applying the most recent edition of the standard indicated below. ANSI S1.13-1971 (R1986), Methods forthe Measure- ment of Sound Pressure Levels Page 1 of 5 pages 3 Definitions 3.1 complete sound reproduction system: Represented diagrammatically in figure 1 and used in television co

6、ntrol and review rooms, con- sisting of a main chain and a monitor chain. 3.2 main chain: That part of the television audio system which includes input transducers, audio, and the audio portion of video tape and/or disk recorders, pretransmitter audio signal process- ing, and the aural transmitter.

7、3.3 monitor chain: That part of the television audio system which includes the monitor fader, monitor equalization, monitor loudspeaker, and room acoustics of the monitor environment. 3.4 electroacoustic response: T h e e I e c t r o- acoustic response of the monitor chain at a point is the sound pr

8、essure level expressed in decibels with respect to a reference level of 20 pPa at 1 kHz measured over the bandwidth of the mea- suring system in use (see annex A) over a given frequency range measured at a given position in the listening area when pink noise is applied to the input of the monitor sy

9、stem. The overall electroacoustic response is made by averaging points in the room by the method specified in 4.2. 3.5 pink noise: A continuous spectrum of random noise exceeding the bandwidth of the object under test having constant energy per constant percentage of bandwidth (equal energy per octa

10、ve). CAUTION NOTICE: This Standard may be revised or withdrawn at any time. The procedures of the Standard Developer require that action be taken to reaffirm, revise. or withdraw this standard no later than five years from the date of publication. Purchasers of standards may receive current informat

11、ion on all standards by calling or writing the Standard Developer. Printed in USA. Copyright 0 1994 by THE SOCIETY OF - American Nalional Standard MOTION PICTURE AND TELEVISION ENGINEERS 595 W Hartsdale Ave, White Plains. NY 10607 (914)761 1100 Approved October 19, 1994 SMPTE 222M 94 8357401 00017b7

12、 bb5 I NON-SYNC pt-7 I i I I ANSI/SMPTE 222M-1994 1 1 1 MAIN CROSSOVER NETWORK I FADER MAIN CHAIN MONITOR CHAIN VIDEO I RECORDER Figure 1 - Complete television sound reproducing system 4 Method of measurement L = 10 logia 4.1 The electroacoustic response shall be measured with the equipment and inst

13、ruments arranged in accordance with figure 2. 4.2 Sound pressure level vs frequency measure- ments shall be made as follows: a) in dubbing control rooms, at each of the principal listening areas; b) in review rooms, at a sufficient number of posi- tions to cover the listening area. To obtain a valid

14、 representation of the acoustic response throughout the listening area, it is suggested that at least three positions be averaged when employing whole-octave bands, and at least five positions when employing third-octave bands. Averaging shall be done by the sum of the squares of the sound pressure

15、levels as follows: E k=l N antiiogio (:I: 1 N where N is the number of positions and Lk is the sound pressure level at each position. If the range of sound pressure levels lies within 4 dB, simple arithmetic averaging is sufficiently accurate to be used. 4.3 It is recommended that measurements be ma

16、de at a normal seated head height between 1 rn and 1.5 rn (3.3 ft and 4.9 ft) and not closer than: a) 1.5 rn (4.9 ft) to any wall; b) 2 m (6.6 ft) to the loudspeakers. 4.4 A suitable single loudspeaker sound pres- sure level with pink noise is 85 dB (flat or linear), but the spectral level in any th

17、ird-octave band shall exceed the background noise in the band by at least 10 dB, or by 4 dB if adjusted accord- ing to ANSI S1.13. Page 2 of 5 pages SMPTE 22211 94 8357403 0001768 5TL RMS VOLTMETER o POWER ANSI/SMPTE 222M-1994 (CONTROL ROOM) MEASURING SPEAKER UNITS IN STRUMEN1 I AMPLIFIER NOISE FILT

18、ERS MAIN CROSSOVER SOURCE FADER NETWORK MEASURING bLI:e MICROPHONE Figure 2 - Method of measurement of monitor chain (Optional equipment shown with dotted lines) 4.5 It is recommended that measurements be made with a microphone small enough so that high-frequency response errors due to diffrac- tion

19、 effects about the microphone are minimized. A microphone having a difference between the direct O“ incidence and random incidence responses less than the tolerance specified in table 1 is preferred (see annex A.5). 4.6 Measurements of low-frequency response in small rooms are strongly influenced by

20、 individual room modes. The effect of room modes can be FILTER minimized by averaging the response at a large number of locations in the room (see annex A.4). 5 Characteristics The electroacoustic response of the monitor chain shall be within the tolerance of the curve in figure 3 and table 1. This

21、response is satisfactory for monitor- ing of all types of tracks at the monitor point in figure 1, including monitoring of film tracks after appropriate deemphasis, such as an Academy filter for monaural tracks, has been applied. dB dB +4 -2 o -2 -4 -6 -8 - 10 -12 -14 - 16 - 18 +4 +2 O -2 -4 -6 -8 -

22、 10 - 12 - 14 - 16 - 18 I 2 4 5 6.3 e IO 12.5 16 31.5 40 50 63 80 100 Hz KHr NOTE - Tolerances are based upon V3 octave measurements. If 1/1 octave measurements are used, reduce tolerance by 1 dB. Figure 3 - Curve of monitor chain characteristic Page 3 of 5 pages - SMPTE 22211 94 8357403 0003769 438

23、 ANSI/SMPTE 222M-1994 Table 1 - Monitor chain characteristic Central frequencies of one-third octave bands Characteristic To I e rances HZ dB 31.5 40 50 63 80 1 O0 125 160 200 250 31 5 400 500 630 800 1 O00 1250 1600 2000 2500 31 50 4000 5000 6300 8000 10 O00 12 500 16 O00 -10 -7 -5 -3 -1 O O O O O

24、O 0. O O O O O O O - 0.5 - 1.0 - 1.5 - 2.0 - 2.5 - 3.0 - 3.5 - 4.0 - 4.5 + 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 dB - 8 7 6 5 4 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Page 4 of 5 pages SMPTE 222M 94 8357401 O001770 IST ANSIJSMPTE 222M-1994 Annex A (informative) Additional da

25、ta A.l This standard refers to the monitor chain which includes the reproduction equipment as shown in figure 1 and the listening area in the control or review room. It is emphasized that, in practice, satisfactory reproduction of sound in a control room or a review room is also depen- dent upon the

26、 alignment and performance of the principal chain equipment in the installation. It is therefore essential that the elements of the principal chain be correctly aligned within the tolerances of existing or proposed standards and practices by the use of appropriate photographic or mag- netic test tap

27、e or film, and, in the case of reproducing photographic film or magnetic masters that were mixed for monaural photographic film and intended for playback through an Academy filter, that the relevant deemphasis network be applied. A.2 The monitor chain response in this standard represents industry pr

28、actice, but may result in inadequate monitoring at the lower bass end. A bass response which is flat to a lower frequency is more desirable for future television audio monitoring as loudspeakers are improved in the consumer market. A.3 At least five methods of measurement are recognized as providing

29、 appropriate data for the evaluation of the electro- acoustic response of the monitor chain. The methods depend on the generation of pink noise with flat frequency response from 31.5 Hz to 16 kHz or beyond, and are as follows: a) Generate wide-band pink noise and measure the acoustic output with a c

30、alibrated microphone intended for use in the diffuse field and *an audio-frequency, constant-percentage- bandwidth spectrum analyzer, such as a %octave band analyzer. b) Generate pink noise in 1/3-octave bands conforming to the requirements for class II third-octave band filters, Annex B (informativ

31、e) Bibliography ANSI S1.4-1983, Specification for Sound Level Meters specified in ANSI S1.11. Measure the output sound pressure levels with a microphone and true-rms meter conforming to the requirements for a type 1 sound level meter specified in ANSI S1.4. c) Generate wide-band pink noise and measu

32、re the acoustic output with an rms voltmeter and sound level meter as in b) above, reading the acoustic output through a series of 1/3- octave bandpass filters. d) Generate pink noise in octave bands, the center frequencies of which shall be altered in either VI- or %octave steps. Measure the acoust

33、ic output with a sound level meter as described in b). This procedure, using full-octave bands, requires that tolerances on the monitor chain electro- acoustic response curve be reduced as noted in figure 3. e) Generate pink noise and, with a calibrated microphone intended for use in the diffuse fie

34、ld and a precision tape recorder, record the microphone signal as a function of both frequency and position in the control room. Reproduce and analyze the results by one of the methods described above at a subsequent time in an appropriate laboratory. The pink noise test signal should be at such a l

35、evel in the room as to be clearly louder than any ambient noise (air conditioning, traffic rumble, video tape recorders, etc.). The level should not be so loud as to risk loudspeaker damage or power amplifier clipping. A.4 Care should be taken that none of the microphone placements chosen is extraor

36、dinary. Positions should be avoided which are exactly on lateral or transverse room centerlines. A.5 A microphone satisfying the requirements of 4.5 will generally have a diameter of approximately 1/4 in. ANSI S1.11-1986, Specifications for Octave-Band and Fractional Octave-Band Analog and Digital Filters Page 5 of 5 pages