1、 1 Scope This practice specifies a type U (see 6.1) audio frequency test film to be used for adjusting the sensitivity and frequency response of 35-mm motion-picture magnetic studio audio reproducers operating at 96 perforations per second or approximately 90 ft (27 m) per minute for use with one-,
2、three-, four-, and six-track audio systems. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this practice. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parti
3、es to agreements based on this practice are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. ANSI S4.3-1982 (R1992), Method for Measurement of Weighted Peak Flutter of Sound Recording and Reproducing Equipment ANSI S4.6-1982 (R1992), Met
4、hod of Measuring Recorded Flux of Magnetic Sound Records at Medium Wavelengths ANSI/SMPTE 86-1996, Motion-Picture Film Magnetic Audio Records Two, Three, Four and Six Records on 35-mm and One Record on 17.5-mm Magnetic Film SMPTE 139-2003, Motion-Picture Film (35-mm) Perforated KS SMPTE 223M-2001, M
5、otion-Picture Film Safety Film 3 Test film signal 3.1 Frequencies The audio record shall be a recording which will reproduce at the frequencies specified in 6.4 when the linear speed of the film is 96 perforations per second or approximately 90 ft (27 m) per minute (18 in or 45.7 cm per second). 3.2
6、 Distortion The total harmonic distortion of the recorded reference signal (see 6.1) shall not exceed 0.2%. 3.3 Audio record The audio record shall be recorded so that it extends from one edge of the film to the other. Page 1 of 4 pagesRP 127-2004 Revision of RP 127-1999 Copyright 2004 by THE SOCIET
7、Y OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100 Approved November 8, 2004 SMPTE RECOMMENDED PRACTICE Specifications for Type U Audio Level and Multifrequency Test Film for 35-mm Studio Audio Reproducers, Magnetic Full-Coat Type RP 127-2004 Pa
8、ge 2 of 4 pages 3.4 Signal fluctuations The signal levels shall not fluctuate more than 0.5 dB within each test section length. 3.5 Flutter The weighted peak flutter of the audio record shall not exceed 0.04% when measured in accordance with ANSI S4.3. 3.6 Azimuth The azimuth of the audio records sh
9、all be 90 3 to the reference edge of the film. 3.7 Signal identification Each test section and segment shall be preceded by voice announcements identifying the content at a level whose peak value does not exceed peak level of the frequency series. 4 Film stock 4.1 The film stock shall be full-coat,
10、splice-free, and of the low-shrinkage, safety type in compliance with SMPTE 223M. 4.1.1 Test films shall be cut and perforated in accordance with dimensions specified in SMPTE 139. 4.2 The film stock shall be conditioned for 10 days at 20C 3C (68F 5.4F) at a relative humidity of (50 10)% prior to re
11、cording. 4.3 The film shall be recorded and packaged within the temperature and humidity limits specified in 4.2. The recorded film shall be packaged in a metal can and sealed either with a low-moisture permeability plastic tape or a fabric tape having a moisture barrier. 5 Identification Each test
12、film shall be suitably identified to include the date of manufacture. 6 Test sections 6.1 Reference level A sine wave with a frequency of 1000 Hz 2% shall be recorded ahead of the azimuth section, having an absolute short circuit record level of 185 nWb/m 10 nWb/m, for a duration of approximately 30
13、 seconds. (This film is classified as a type U by the ISO because of the 185 nWb reference level, as compared with the type E which specifies a 320 nWb reference level.) 6.2 Azimuth A frequency of 16 kHz 2% shall be recorded ahead of the pink noise section having an absolute short circuit recorded l
14、evel of 25.89 nWb/m for a duration of approximately 30 seconds. 6.3 Pink noise The pink noise test signal used for this section shall have equal energy in equal logarithmic frequency intervals within the audio bandwidth. The lower limit shall correspond to the lower bandwidth of a 31.5-Hz octave ban
15、d filter of the ANSI class II type, and the upper limit to the upper bandwidth of a 16-kHz octave RP 127-2004 Page 3 of 4 pages band filter of the ANSI class II type. (Test bandwidths must be within these limits.) The level in each one-third octave band from 40 Hz to 12.5 kHz shall be the same withi
16、n 1 dB. The pink noise signal shall be recorded so that there shall be a low statistical probability of the extreme peaks within the signal saturating the magnetic film. The peak level of the wide band pink noise spectrum shall be essentially equal to that of the corresponding frequency response tes
17、t segments. The recorded pink noise shall have the characteristic specified in 6.5 and a duration of approximately 30 seconds. (The pink noise may also be used for multitrack azimuth adjustment using an oscilloscope lissajous figure from the two outside tracks of multitrack equipment.) 6.4 Frequency
18、 response The 1000-Hz frequencies of this multifrequency section shall be recorded at the reference level of 185 nWb/m. The following test segment frequencies in hertz 2% shall be sine waves recorded in the order given: 1000, 31.5, 40, 50, 80, 100, 160, 400, 1000, 2500, 4000, 6300, 8000, 10 000, 12
19、500, 16 000, 1000. 6.5 Recorded levels With a constant-amplitude sine-wave signal applied to the input of the recording system, the relative characteristic in effective values of the short-circuit magnetic flux versus frequency shall decrease with increasing frequency proportionately to the impedanc
20、e of a parallel combination of a capacitance and a resistance having a time constant of = 35 s. (A time constant is a shortband notation, such as illustrated by a frequency response curve, having a shape which results from a time constant of one or more microseconds. This is a convenient way of defi
21、ning a response curve and is never intended as a recommended electrical circuit.) The characteristic defined above is obtained by the following calculation: Lre 185 nWb/m = 0.20511 10 log101 + (2)2f2 dB where Lis the recorded relative short-circuit magnetic flux level in decibels, f is the frequency
22、 in hertz for which Lis computed, is a time constant of 35 s, and 0.20511 is a constant calculated to make L= 0 at the reference frequency of 1000 Hz. The approximate numerical values are given in table 1. 6.6 Flux level variation The film flux level at each frequency from 31.5 Hz through 16 kHz sha
23、ll be within 0.5 dB of the value specified in 6.5. 6.7 Duration The duration of frequency response test segments shall be approximately 10 seconds, except for the 16-kHz tone which shall be approximately 30 seconds for azimuth and high-frequency equalization adjustment. RP 127-2004 Page 4 of 4 pages
24、 Table 1 Flux levels versus frequency in nanowebers per meter and decibels Frequency, Hz f Short circuit flux1nWb/m Relative level2L 1000 31.5 40 50 80 100 160 400 1000 2500 4000 6300 8000 10 000 12 500 16 000 1000 185.00 189.42 189.41 189.41 189.39 189.37 189.30 188.69 185.00 165.99 142.23 110.86 9
25、3.60 78.41 64.76 51.78 185.00 0.00 + 0.20 + 0.20 + 0.20 + 0.20 + 0.20 + 0.20 + 0.17 0.00 0.94 2.28 4.45 5.92 7.46 9.12 11.06 0.00 1Calculated using the equation = 185 antilog10(L /20). 2Calculated using the equation given in 6.5. 7 Calibration 7.1 Flux The short circuit flux on the test film shall b
26、e determined by means of the calibrated short-gap ferromagnetic core reproducer technique. This technique is described in ANSI S4.6. 7.2 Level The signal level measurements specified in 3.4 shall be measured with an rms voltmeter calibrated in decibels with an accuracy of 0.1 dB over the bandwidth 3
27、1.5 Hz to 16 kHz. 7.3 Method The test film shall be calibrated on a reproducing head made in accordance with ANSI/SMPTE 86. NOTE - A signal level (reference level) test film and a multifrequency test film, made in accordance with this practice and recorded across the width of the film from edge to edge on polyester and triacetate materials, are available from the Society of Motion Picture and Television Engineers.
