OPERATING INSTRUCTIONS /Jri D •. . GENERAL RADIO COMPANY

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SALES ENGINEERING OFFICES

METROPOLITAN CHICAGO * NIW YORK• 660.5 Wo•t Nonlrt A,....,.,. 0et ,.,.,, /l iOOlf, 60302 lteed A~o- ef tl!ldo~t TYPE 1565-A 111/,.ttW, Ntw ).,,,,, 014ST ,.,.,_.., Jl2 14.. . . ft,...,eNY.212N+V2l N.I 2'0194J-JI~ CLEVELAND Wf,Hrl loatl SYRACU$ 1 Cle .....n .I,Or.lo,.UIH fofopll611o216116-0150 "("'"~ a../ldl"t loti Moller I OOfi LOS ANGEll$* SOUND-LEVEL METER tyriKIIII,NtwYollr,I.UIJ foloplriOIIOJIS4jof.fUJ 1000 Norrit teword S1roet lNAn,./u,Coliforl'llo,900JI h/tp/IOftO 2Jl46f.6201 PHI LADILPH I A (;,,.,,,.,,..,,,_ ,110"'7 SAN FRANCISCO 1ortWoJ.Itlo,.,. llldOIJftlolhtlt l f ldlHAitoi AU.ftW fort Wo111l11tf011, ,,,.,.,,h-M/o lfOU lotAtlot,Colllw•do,f-'02.2 hlop~OIIO 21.5 6-U-IOJO h/epllot~o41J f4j4 21l

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GeMtol Rodlo Compony (O,.,,eod, 1001 Zurich, Switrlfrlortd C.nerol Radio Componr CU.IC.J limn.d, lourne fncl, lud:inuhom.shire, fnglonc:f RepntentGtiY•• in Principal OY.,no• Countri•• GE NERAL R A D I 0 COMPANY

B OPERATING INSTRUCTIONS

TYPE 1565-A

SOUND-LEVEL METER

Fo•m 156S.0100-B Fob•uo•y , 1965

Copyright 196~ by General Radio Company Wesc Concord, Massachusetts, USA

G ENERAL RAD I O COMPANY WES T CONCORD, M ASSAC HUSE TTS, USA SECTION 1

INTRODUCTION

1.1 PURPOSE. Figure 1. The Type 1565-A Sound-Level Meter Type 1565-A Sound-Level Meter. (Figure 1) is designed for the measure­ ment of A-, B·, or C·weighted sound NOTE levels at its microphone. It is simple and convenient to operate, and it is in­ This book contains the opera­ expensive. It covers the range from 44 ting instructions for the Type to 140 dB, referred to .0002 J-Lbar (the 1565-A Sound-Level Meter. standard reference level). It meets the More detailed information on requirements of both the American noise-m easuring techniques in Standard Specification Sl.4-1961 for general can be found in the General-Purpose Sound-Level Meters General Radio "Handbook of and the IEC Recommendation 123, 1961. Noise Measurement" ($1.00). SPECIFICATIONS Temperature Coefficient of Sensitivity: +0.03 dB;oC. Sound-Level Range: 44 to 140 dB (re 0.0002 Sensitivity to Magnetic Fields: Equivalent C­ ~

1.3 CONTROLS. The following controls and connec­ tors are on the sound-level meter (numbers refer to Figure 2):

1. Eight-position rotary switch turns instrument on or OFF; selects weighting and meter speed; con­ nects meter for battery check. 2. Nine-position rotary switch attenu­ Figure 2. Controls and connectors on ator control; selects meter range. the Type 1565-A Sound-Level Meter.

2 3 1.4 ACCESSORIES. A carrying cord is supplied with the sound-level meter. A stud fastened to the strap mates with a threaded insert in the bottom end of the case. The available accessories include: Type 1565-P 1 Leather Carrying Case; Type 1560-P96 Adaptor to adapt the input socket to mate w.ith a standard, 3-terminal, male, microphone connector for connection to a vibration pickup, SECTION 2 cable, or other transducer. Type 1560-P95 Adaptor Cable to con­ OPERATING PROCEDURE nect the output to the Type 1521-B Graphic Level Recorder or other device fitted with jack·top binding posts on 2.1 CHECKING THE BATTERY. 3/4-inch centers; Always check the battery before the Type 1560-P52 Vibration Pickup • instrument is used. Turn the left-hand (refer to paragraph 2. 7). knob to the BAT position. The meter must indicate in the region marked .. BAT. If it does not, the battery must be replaced. To do this, unscrew the large knurled nut above the knobs and remove the plastic nose cone. Remove the battery; then replace it with a Ray· 0 -Vac "C" cell, Type 1LP, or equiva­ lent. Be s ure the spring contacts are clean and are pressing on both termi­ nals. Observe the proper polarity: the 4 5 raised center terminal of the battery greater than this, set the left-hand should contact the spring marked +. knob to Cs (Cslow). The fluctuations The battery life is about 35 hours of the meter will be markedly reduced, if used two hours per day, or about and an average level can then be readily 20 hours with continuous use. estimated. The sound level should be measured If the instrument is to be stored for with each of the three weighting char­ an extended period or in an ambient acteristics. After determining the C­ temperature above 100 °F, remove the weighted level, follow the same pro­ battery, to avoid the corrosive effects .. cedure with the left-hand knob at B; of battery leakage. then repeat the procedure with the knob at A. 2.2 BASIC OPERATION. The weighting should always be in­ Stand with the instrument in front of cluded when a statement of sound level you, with the sound coming from the is given; without the weighting char­ side. Point the microphone in a direc­ acteristic being known, the statement tion perpendicular to that from which is meaningless. the sound is coming. 2.3 CHOOSING THE WEIGHTING Set the left-hand knob to CF (CFast) CHARACTERISTIC. and turn the right-hand knob until an on­ scale meter indication is obtained. The Noise codes and acceptance-test pro­ C-weighted sound level is the algebraic cedures frequently specify the weight­ sum of the level indicated by the meter ing characteristic to be used. For and the setting of the right-hand knob example, A w.el.&htiog is often used for (attenuator). For example, if the meter the measurement of traffic, office, or indicates +4 and the attenuator setting plant noise. 1 When no standard test is 70, the C-weighted level is 74 dB. 1 If the fluctuations of the meter cover R. W. Young, Journal of the Acoustical ~ciety of America, Vol. 36, pp. 289·295 (1964). 3 dB or less, use the average level in­ D. P. Loye, Noise Control, Vol. 5, pp. 230· 235, dicated. When the fluctuations are July, 1959. 6 7 •I0 procedure is involved, measurements C WEIGHTI WEIGHTING= should be made with each of the three 0 weighting characteristics. 8 AND ~1E~KT1NG ~ The frequency response of the sound­ level meter for each weighting char­ h iz."wtloHn ~WEIG~TIN acteristic is shown in Figure 3. The C-weighting curve is nearly uniform over the frequency range from 32 c/s to 8 kc/s, thus giving an indication of the over-all sound pressure. The A-weight­ ing characteristic discriminates heavily 20th 100 200 500 t•tls 2 10 20 against low-frequency sounds to give an "" FREOUENCY indication closely correlated with sub­ Figure 3. Typical A-, 8-, and C- jective estimates of loudness, an­ weighted random-incidence responses noyance, and speech interference. The of the sound-level meter. B-weighting characteristic, between the A and C curves, is sometimes used in place of A weighting when the sub­ tor Oscillator is small in size and is jective effects of noise are of interest. battery operated, making it ideal for When a frequency analyzer is to be field use. used with the sound-level meter, set The calibration procedure 1s as the weighting switch to C. follows: .. Unscrew the large knurled nut that surrounds the microphone and remove 2..4 CALIBRATION. the nose cone. Set the left-hand knob A simple, reliable, over-all, level cal­ to CF and place the calibrator over the ibration can be obtained by means of a microphone. Adjust the screwdriver Type 1552-B Sound-Level Calibrator, control between the knobs on the panel driven by a suitable oscillator set to of the sound-level meter for an indica­ 400 c/s. The Type 1307-A Transis- tion of 120 dB (110 on the attenuator 8 9 and +10 on the meter). NOTE: This le~el should be observed, giv.ing a peri­ calibration will be made free oi -charge odtc check on the meter calibration. at any General Radio office. Alternatively, the meter can be 2.5 EFFECT OF THE OPERATOR'S checked by less sophisticated methods. PRESENCE. For example, any source that is rea­ .. When the sound is coming mainly from sonably constant from day to day can be one direction, the sound-level reading used as a reference. A particular dial may be somewhat affected by the rela­ tone of a telephone, the drone of an office machine, or simply the back­ tive positions of instrument and ob­ server. The Type 1565-A should not be ground noise in an office may be ade­ quate. Measure the A-weighted sound held in front of the observer with che microphone pointed toward the source of level of the reference sound source when the Type 1565-A is first received, the sound, although this is perhaps the when it is known to be operating pro­ most logical manner. This position perly. Note the position and orien­ gives a marked increase in the response • at high frequencies. The observer fac­ tation of the meter relative to the the sound from directly behind the sound. Subsequent periodic sound­ ~ng mstrument, acts as a reflector to pro­ level measurements should agree with duce errors of several decibels in the this original value within 2 or 3 dB. •• frequency range above 100 c/s. A voice can also be used for a simple A more uniform frequency response check. In a fairly quiet room, hold the is obtained with the sound-level meter sound-level meter at arm's length and, in front of the observer, but with the speaking directly into the microphone, sound grazing the microphone (coming repeat a simple sentence, such as, from the side, rather than from the front). "What level does the meter read?" When out of doors, hold the instrument Note the sound level. U this check is with the microphone pointing upward, repeated periodically by the same ob­ (to avoid interference from reflected server, in the same location, with the high frequencies) and as far from the same background noise, the same sound

10 11 r body as is convenient. Do not point the microphone toward a source of back­ 1400 ~ ground noise (any source other than the ~ one being measured). 1200 12 CABLE LOSS The souad,level meter can be mounted 1000 10 .. on a tripod to reduce further the effects of the observer' s presence. His posi­ 800 s:!' ~ tion should be similar to that for hand­ g held operation; a line between the 600 CAPACITAN11CE ·~ observer and the instrument should be .. 400 4:l approximately perpendicular to a line

from the instrument to the sound source. 200 2.6 USE OF AN EXTENSION CABLE. 200 400 600 800 1000 1200 1400 160% The sound-level meter can be oper­ CAPACITANC E OF CABLE (pF) 1 ated at some distance from its micro­ phone if an extension cable, such as Figure 4. The compensation required the Type 1560-P73, is used. However , for the capacitance of various extension several factors must be considered: cables. Chart also shows the corres­ ponding cable loss. The use of the cable will change the source impedance as seen by the input ing capacitor for cable capacitances terminals of the sound-level meter, thereby changing the weighting charac­ between 150 and 1500 pF. teristics. To compensate for this, a The T ype 1560-P73 Extension Cable, capacitor must be added in series with for use with the Type 1565-A Sound­ the input to the sound-level meter. Level Meter, is a 25-foot cable, fitted Also, cable losses will cause the meter with standard 3-terminal microphone to read low by an amount that varies connectors. A T ype 1560-P96 Adaptor with the cable length. Figure 4 shows and a Type 1560-3040 Microphone Base the loss and the value of the compensat- are needed to mate the sound-level meter and the microphone with the con· 12 13 TYPE 1560-P96 AOAPTOR, MOOIFIEO TO INCLUOE nectars. The capacitance of the Type SERIES CAPACITOR 1560-P73 Extension Cable rs ap­ ~- MICROPHONE REMOVEO FROM ~ TYPE 1565-A proximately 550 pF. Figure 4 shows 0 0 that a series capadtor of 640 pF is re­ TYPE 1565-A Cl=z:P..-~ L~ quired for this cable capacitance. This SOUNO-LEVEL METER ~ J' capacitor can be installed in the Type TYPE 1560-3040 MICROPHONE BASE 1560-P96 Adaptor, as follows: • Figure 5. Installation of an extension Remove the outer shell of the adaptor. cable between sound-level meter and To do this, turn the setscrew located the microphone. in the hole in the side of the shell in a clockwise direction. Remove the lead connecting terminal No. 3 of the micro­ lei to its axis. Replace the microphone phone connector to one of the teflon cartridge with the modified Type 1560- insulated pin plugs, and replace the P96 adaptor, oriented so that the termi­ lead with a small mica or ceramic ca­ nal marked G on the sound-level meter pacitor of about 640 pF. Then replace mates with the terminal marked G on the the outer shell. adaptor. The value of capacitance to be used Next, push the pin jack attached to with other cables can be determined the black lead in the Type 1560-3040 from Figure 4. Microphone Base onto the pin marked L To connect an extension cable, pro­ on the microphone and push the white­ ceed as follows (see Figure 5): lead pin jack onto the other pin. Fasten Unscrew the knurled nut around the the microphone base to the cartridge by microphone cartridge on the sound-level means of the setscrews in the base. meter and remove the plastic no"se cone. The extension cable can now be in­ Turn the two setscrews on opposite stalled between the sound-level meter sides of the microphone cartridge in a and the microphone base. The loss for clockwise direction and remove the cart­ the Type 1560-P73, 25-foot Extension ridge by sliding it in a direction para!- Cable is found from Figure 4 to be , . 15 7.8 dB. This value must be added to the reading of the sound-level meter to obtain the actual sound level. Or the correction can be detennioed with the Type 1552-B Sound-Level Calibrator, which produces a level of 120 dB at the microphone (refer to paragraph 2.4). When replacing the microphone on the sound-level meter, be sure the micro­ phone terminal marked L mates with the socket terminal marked G. The Type 1560-P73, 25-foot Exten­ sion Cable i s available with the Type 1560-P32 Tripod as the Type 1560-P34 Tripod and Extension Cable. •

2.7 USE AS A VIBRATION METER. Figure 6. The sound-level meter fitted 2.7.1 INSTALLATION. with the Type 1560-P96 Adoptor and the Figure 6 shows the Type 1565-A Type 1560-P52 Vibration Pickup. Sound-Level Meter fitted with the Type • 1560-P96 Adaptor and the Type 1560-P52 Vibration Pickup. The microphone is 2.7.2 CALIBRATION. replaced with the adaptor, as in para­ One method of calibrating the sound­ graph 2.6, but in this case the adaptor level meter uses the Type 1557-A requires no modification. The vibration Vibration Calibrator, as follows: pickup includes a shott cable fitted Remove one of the 50-gram disks from with a three-terminal microphone con­ the calibrator and mount the pickup in nector that mates with the adaptor. 16 17 its place. (The cable mus e be free and indication of +2 dB. Install the pickup unrestricted.) Sec the calibrator on a and use Table 1 to convert indicated dB level surface and turn it ON. Adjust levels to acceleration in g's, rms. The the LEVEL control so chat the meter technique for measuring vibration is indicates 100. Set the left-hand knob on given in the GR Handbook of Noise the Type 1565-A co CF and the right­ Measurement. The frequency response hand knob to llO. Adjust the meter for the combination of the Type 1565-A indication to +2 dB by means of the Sound-Level Meter and the Type 1560- screwdriver control on the panel, be­ ; P52 Vibration Pickup is shown in tween the knobs. The meter will now • Figure 7. indicate a level of 112 dB when the pickup is subjected co an acceleration 2.8 BACKGROUND NOISE. of one g, ems (386 inches per second Measurements should be made with as per second). Use Table 1 to convert little background noise as possible. indicated levels in dB co acceleration For all weightings the background level in g's, rms . should be at least 10 dB below the total The sound-level meter can also be measured level. When chis cannot be calibrated by electrical means when the done, apply the corrections given in sensitivity of the Type 1560-P52 Vibra­ Figure 8. tion Pickup is known. Install the Type 1560-P96 Adaptor; then apply a voltage numerically equal to the pickup sensi­ tivity in volts per g between terminals No. 1 and No. 3 of the adaptor input. (Terminal No. 1 is grounded co the in­ strument case). Sec the knobs on the sound-level meter to CF and llO dB. The oscillator frequency should be be­ tween 100 and 1000 c/s. Adjust the panel screwdriver control for a meter 18 19 TABLE 1 TABLE 1 (CONT)

ACCELERATION IN. g's CORRESPONDING Level Accel Level Accel TO VARIOUS INDICATED LEVELS in dB in g's in dB in g' s 88 .0631 114 1.26 Level Accel Level Accel 89 .0708 115 1.41 in dB in g's in dB in g's 90 .0794 116 1.59 91 .0891 117 1. 78 44 .000398 .00501 66 92 0.100 118 2.00 45 .000447 67 .00562 ~ 93 .112 119 2.24 46 .000501 68 :oo631 94 .126 120 2.51 .00708 47 .000562 69 95 .141 121 2.82 48 .000631 70 .00794 96 .159 122 3.16 .000708 .00891 49 71 97 .178 123 3.55 .000794 \ 50 72 .0100 98 .200 124 3.98 .000891 51 73 .0112 99 .224 125 4.47 52 .00100 74 .0126 100 .251 126 5.01 53 .00112 75 .0141 101 .282 127 5.62 54 .00126 76 .0159 102 .316 128 6.31 55 .00141 77 .0178 ' 103 .355 129 7.08 56 .00159 78 .0200 104 .398 130 7.94 57 .00178 79 .0224 105 .447 131 8.91 58 .00200 80 .0~ 51 106 .501 132 10.0 59 .00224 81 .0282 11.2 60 .00251 82 .0316 107 .562 133 61 .00282 83 .0355 108 .631 134 12.6 62 .00316 84 .0398 109 .708 135 14.1 63 .00355 85 .0447 110 .794 136 15.9 64 .00398 86 .0501 111 .891 137 17.8 65 .00447 87 .0562 112 1.00 138 20.0 113 1.12 139 22.4 20 140 25.1 21 7

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~ 41 1 c "g (\J 41 Gi...c -·-.. .. s. 41 0 ~ Gi SECTION 3 -- c - 41 >- g > 0 8~ u - ...c lOW ·c. e ~ PRINCIPLES OF OPERATION :J 0 >- i:i w .. 41 ·- a: E ... ~ "'c 0 0 ·- a.."g 3.1 MICROPHONE. 2 ., 0 ~ ~c.:: General Radio's new lead-zirconate­ 0 >.D 0 ~ u titanate ceramic microphone was de­ ::> c ~ 0141 c veloped as a measurement-grade micro­ ::> 41 IL. ere> phone. With a diameter of 0.936 inch, I· it fits into any fixture designed to ac­ ~ cept the current industry-standard Western Electric 640-AA Condenser ~ Microphone. A typical free-field fre­ 0" v (\J 0 (\J vN quency-response curve for the new + + I I microphone is shown in Figure 9. S1381:>30

24 25 3.2 CIRCUIT. the Type 1565-A Sound-Level Meter The all-solid-state circuit (Figure 11) serves double duty, also forming part contains a total of seven transistors in of the weighting network. To achieve two amplifier stages and the power the A-weighting characteristic, for supply. example, the feedback network in the The preamplifier includes transistors main amplifier provides a roll-off of QlOl and Ql02. The former is a special 6 dB/octave at both 733 c/s and at N-channel field-effect transistor, operat­ 8 kc/s. The coupling network between ing as a "source follower.'' The gain the preamplifier and the main amplifier adds roll-off starting at 32 c/s, and the of the second transistor, Q102, can be combination of the input resistance of adjusted by means of a panel screw­ the instrument and the microphone driver control, to calibrate the instru­ capacitance yields an additional slope ment. of 6 dB/octave, starting at 107 c/s. The main amplifier uses four tran­ sistors, including a complementary Since the equivalent microphone ca­ pair, Q105 and Q106, at the output. pacitance serves as part of the weight­ Feedback is applied to the emitter of ing network, the spectrum is partly Q103 to stabilize the voltage gain. weighted before it is introduced to the This amplifier feeds both the meter­ preamplifier, which reduces the likeli­ detector dr.cuit and the output .ter­ hood of overloading the amplifier. The minals. source capacitance cannot be changed, The attenuator is separated into two however, without affecting the weight­ sections for best signal-to-noise ratio. ing characteristic. One secti()n is located directly at the input; the other is between the amplifier 3.3 POWER SUPPLY. stages. The panel control, calibrated The unique power supply includes a from 50 to 130 dB, adjusts the at­ simple de-to-de converter, to permit tenuation in 10-dB steps. operation from a single 1. 5-volt C cell. Each coupling and feedback path in The circuit is basically a tuned, self-

26 27 biased, class-C oscillator, operating at a frequency of 130 kc/s. The ac output voltage from the transformer is applied to a full-wave voltage doubler rectifier consisting of diode CRl, the transistor base-emitter junction, and ca­ pacitors Cl and C2. Half of the de output voltage biases the transistor in the cur-off region, affording the desired class-C operation, with a conversion efficiency of about 70 per­ cent. The high efficiency of power supply and amplifier makes possible a battery life of 35 hours; it is therefore unnecessary to turn the instrument on SECTION 4 and off during a series of measure­ ments, to conserve the battery. SERVICE AND MAINTENANCE

4.1 GENERAL. General Radio warrants that each new instrument sold by us is free from defects in material and workmanship, aad that, properly used, it will perform in full accordance with applicable specifications for a period of two years after original shipment. Any instru­ ment or parr that is found within the two-year period not to meet these 29 28 standards after examination by our 4.2 DISASSEMBLING THE factory, district office, or authorized INSTRUMENT. repair agency personnel, will be re­ paired, or, at our option, replaced with­ To remove the nose cone, simply out charge, except for tubes or bat­ unscrew the large knurled nut above teries that have given normal' service. the knobs on the panel. The two-year warranty stated above Removal of two screws, below the attests the quality of materials and battery springs, will permit removal of workmanship in our products. When the back cover. difficulties do occur, our service engi­ neers will assist in any way possible. Turn the two screws on either side If the difficulty cannot be eliminated by of the microphone in a clockwise direction to remove the microphone. Be use of the following service instruc­ sure to tighten them (CCW) when the tions, please write or phone our Service microphone is replaced. Use a small Department (see rear cover), giving full information of the trouble and of steps Allen-type wrench. taken to remedy it. Be sure to mention the serial and type numbers of the in­ strument. Before returning an instrument to 4.3 TRANSISTOR VOLTAGES. General Radio for service, please write Table 2 gives the normal voltages to our Service Department or nearest from the indicated transistor terminals ~ales engineering office, requesting a to ground, with a fresh battery installed Returned Material Tag." Use of this in the instrument. A deviation of ten tag will ensure proper handling and percent from these figures should be identification. For instruments not allowed. Set the left-hand knob on the covered by the warranty, a purchase panel to C F and the right-hand knob order should be forwarded to avoid to 130; use a vacuum-tube voltmeter unnecessary delay. for the measurements. 3o 31 TABLE 2 4.4 INTERNAL NOISE . TRANSISTOR VOLTAGES Table 3 gives the typical internal noise levels measured in octave bands DC Volts for each setting of the right-hand knob {attenuator). To measure the internal Transistor Terminal to ground noise levels, replace the microphone Q101 Drain 10.8 with a 380-pF capacitor (the equivalent (TR-32/C620A) Source 4.6 Gate 3.9 Q102 E 4. 1 TABLE 3 (TR-47/2N2714) B 4.6 Octave-band noise levels measured 13.0 c at the output jack, referred to the out· Q103 E 8.8 put leve l corresponding to full· (TR-777SE-4002) B 9.3 scale meter deflection. 20.4 c ATIENUATOR SETIING IN DB Q104 E 20.6 no 120 110 100 90 80 70 60 50 (TR-ll/ 2N1377) B 20 .5 31.5 76 65 75 65 75 65 54 44 34 c 10.8 p: 63 73 62 72 62 72 62 ..52 42 32 Ill !-< ~ 125 72 61 71 61 71 &l 5 1 41 3J Ql05 E 10.8 z~ Ill u 250 71 61 71 61 71 61 50 40 30 (TR-4/2N 1304) u~ B 10.8 71 6 1 70 60 71 61 50 40 30 c 22.1 o> 500 ~~ 1000 71 61 70 60 71 61 50 40 30 59 71 61 50 40 30 Q106 E W.8 fll~ 2000 71 61 69 ~>j O' 71 61 68 58 72 62 51 41 31 (TR-5/2N1305) B 10.8 >Ill 4000 c 0

MICROPHONE SENSI· METER INDICA· 4.5 ELECTRICAL CALIBRATION. TIVITY IN DB RE TION WITH ATTENU· The over-all gain of the amplifier can 1 VOLT/J.L BAR ATOR SET TO 130 be checked and adjusted as follows: +1 Apply 1 volt at 400 c/s or 1 kc/s to ·57 the sound-level meter through a ·58 +2 shielded 380-pF capacitor connected in ·59 +3 place of the microphone. Set the left· -60 +4 hahd knob (weighting) to CF and the -61 +5 right-hand knob (attenuator) to 130 dB. -62 +6 The correct meter indication depends -63 +7 34 35 4.6 OVER-AL L CA LIB RATION. ACCESSORY INSTRUMENTS The procedure for obtaining a pres­ sure calibration by means of the GR TYPE 1552-B Type 1552-B Sound-Level Cali brator SOUND-LEVEL CALIBRATOR is de scribed in paragraph 2.4. This calibration will be performed free of A convenient accessory ins trument charge at any General Radio Offi ce. for checking the calibration of sound­ A wide -frequency-range pressure level meters , including the circuitry calibration c an also be performe d using and the microphone (whether ceramic, the GR Type 1559-A or -B Microphone crystal, dynamic, or condenser). Reciprocity Calibrator. Refer to the Requires a signal of 2 volts at 400 c/ s, Operating Instructions for these instru­ which can be obtained from the Type ments. 1307-A Transistor Oscillator.

TYPE 1307-A TRANSISTOR OSCILLATOR

Provides simple, accurate calibra­ tion of vibration pickups and measur­ ing systems. This battery-operated in­ strument offers single-frequency (100 c/ s) calibration of accelerometers ranging in mass up to 300 grams, in­ cluding the GR vibration pickups and the accelerometers from other manu­ facturers.

36 37 PARTS LIST ACCESSORY INSTRUMENTS (cont) CAPACITORS C101 Ceramic, .0022f!F ±20% 500V 4404-2220 TYPE 1557-A Cl02 .Olf!F +80-20% 50V 4401-3100 VIBRATION CALIBRATOR C103 .01f!F +80-20% 50V 4401-3100 C104 " 0.68pF ±10% 500V 4400-0068 Provides a 400- and 1000-cycle C105 82pF ±5% 500V 4404-0825 source of power for use with the Type C106 Paper, 1552-B Sound-Level Calibrator. A con­ .01f!F ±10% 100V 4860-7750 C107 Electrolytic, venient audio-frequency source for 10f!F +100-10% 25V 4450-3800 general testing requirements. Cl08 40f!F +100-10% 6V 4450-3600 Cl09 10f!F +100-10% 25V 4450-3800 CliO Paper, .091f!F ±5% 100V 4860- 7889 Cll1 Electrolytic, 4450-2900 TYPE 1556-A " 60f!F +100-10% 25V Cll2 5f!F +100-10% 50V 4450-3900 IMPACT-NOISE ANALYZER Cll3 Mica, 51pF ±5% SOOV 4640-0316 An amplifier-voltmeter system de­ Cll4 Electrolytic, signed to measure peak value and time 40f!F +100-10% 6V 4450-3600 duration of impact sounds or vibrations. Cll5 60f!F +100-10% 25V 4450-2900 Operates from the output of a sound­ Cll6 5f!F +100-10% 50V 4450-3900 Cll7 " l.5f!F ±20% 20V 4450-4400 level meter or a noise analyzer. Cll8 Sf!F +100-20% 50V 4450-3900 Cll9 " l.5f!F ±20% 20V 4450-4400 C120 40f!F +100-10% 6V 4450-3600 C121 " 0.68f!F ±10% 50V 4450-4315 C122 10f!F +100-10% 25V 4450-3800 C123 Ceramic, 270pF ±10% 500V 4404-1278 C124 Electrolytic, 1.5f!F ±20% 20V 4450-4400 C125 Ceramic, 270pF ±10% ·500V 4404-1278 38 39 PARTS LIST (Cont) PARTS LIST (Cont) RESISTORS R127 " 2.55kQ ±1% 1/8W 6250-1255 R128 " 332Q ±1% l/8W 6250-0332 RIO! Composition, R129 Composition, lOOkQ ±5% l /4W 6109-4105 • 300kn ±5% l/4W 6099-4305 Rl02 Film, R130 " 3.3kQ ±5% l / 4W 6099-2335 2.94MQ ±1% l/4W 6250-4294 Rl31 " 24kQ ±5% 1/4W 6099-3245 Rl03 " 4.32MQ ±1% l/4W 6250-4432 R132 " 20kQ ±5% 1/4W 6099-3205 Rl04 Composition, RI33 " 2. 7kQ ±5% 1/ 4W 6099-2275 ±5% Selected in GR Laboratory R134 " 18kQ ±5% 1/4W 6099-3185 RI05 " 12MQ ±5% l/4W 6099-6125 RI35 " lOOkn ±5% 1/4W 6099-4105 RI06 Film, RI36 " 300kQ ±5% 1/2W 6100- 4305 1.27MQ ±1% l /8W 6250-4127 R137 " 10kn ±5% l /4W 6099-3105 Rl07 Composition, 82kQ ±5% l/4W 6099-3825 MISCELLANEOUS Rl08 " 13MQ ±5% l/4W 6099-6135 RI09 " 47kQ ±5% l/4W 6099-3475 BT101 Battery 1.5V 8410-0100 RUO " 9lkQ ±5% l/4W 6099-3915 CR!Ol Diode 1N34A 6082 -1003 Rll1 " 30kQ ±5% 1/4W 6099-3305 CR102 Diode 1N34A 6082 -1003 Rll2 " 15kQ ±5% 1/4W 6099-3155 CR103 Diode 1N34A 6082 -1003 Rll3 " 510Q ±5% l/4W 6099-1515 Rll4 Potentiometer, Composition Jl01 Jack 4260-1295 2kQ ±20% 6041-2109 M101 Meter 5730-1375 RI15 Film, 130kQ ±1% l/8W 6250-3130 MK! Ol Microphone 1560-2131 RI16 Composition, QlOl Transistor C660 1 8210-1032 3.9kQ ±5% l/4W 6099-2395 Ql02 Transistor 2N2714 8210-1047 RI17 " 9lkQ ±'s% l/4W 6099-3915 Ql03 Transistor SE-4002 8210-1077 Rll8 " IOkn·±5% l/4W 6099-3105 Q104 Transistor 2N1377 8210-1377 Rll9 " 270Q ±5% l /4W 6099-1275 Q105 Transistor 2N1304 8210-1304 R120 " 9W ±5% l /4W 6099-0915 Q106 Transistor 2N1305 8210-1305 Rl21 " 75kn ±5% l/4W 6099-3755 Q107 Transistor 2N1377 8210-1377 Rl22 " 5lkQ ±5% l/4W 6099-3515 Rl23 " 510kQ ±5% l /4W 6099-4515 S101 Switch 7890-3250 Rl24 Film, S102 Switch 7890-3240 20.5kQ ±1% l/8W 6250-2205 S0101 Socket 1565-1010 Rl25 " lOkQ ±1% l /8W 6250-2100 Rl26 " 7320 ±1% l /8W 6250-0732 T Transformer 1565-2020 40 41 C CELL 1.5V

? OUTPUT

PREAMPLIFIER AND WEIGHTING I ATTENUATOR I

Figure 11. Ele mentary schematic dia· gram of the Type 1565-A Sound-Level Meter. Figure 10. Etched-circuit board for the Type 1565-A Sound-Level Meter. AT. OR Ill IIr.---__ _ ,, Figure 12. Schematic diagram of Type 1565-A Sound-Level Meter.

RO C/03 A.T. .Of •• 4 208F

If A.T./0.1 II II II II S/02 1 I II + C/09 I R/09 IOpF-r :vr 41'K Rill : i R/01' 30K I' 82K II II tl ~ t~ ==---- -=-=-==-==.:1:!1 I --~ R108 13111 ~~ ~ C/06 C/08 *RI04 .Of 40pF 0"121 I Rl/3 510 5pF R/21 R/02 R/14 1'5K 2.94111 2K . C/04 ._~~------r------._o_.s_w~~~ccw R/03 0.68pF A.T./.12 4.32111 CliO .091 A. T./18 t------+----

R/05 12111 R/06 /.21'111 1/BW /06F IOSF A.r. ..---· -··~·f---

/"\ ("\, "(OTO~ 0 \ I 1 0 2 11 "' .. A. T.l25•• f---' :..:.::.:R­ ' I R/05.1/0F :;_, 1 ··~•"0 C/04 .. _ I SIOI -< A. T./26 .._-""2-"1000R,_..~ A ..T./14+-~~~ A. T./16~ \ '-,~OSF SIOI,20 1'F \/ \.f~CI05 . 8RII5 ~.'Da "'~>- c.~ S\1 +@ ~~~ S/02

VIEW BOTTOM NOTE UNL.ESS SPECIFIED SOI.RCE 811$£ BASE I. POSITION OF ROTARY SWITCHES S. RESISTANCE IN OHMS DRAIN SHOWN COUNTERCLOCKWISE. K 1000 OHMS M 1 MEGOHM GAr£ EMOCOl.L EM0°0 COLL 2. CONTACT NUMBERING OF SWITCHES 6. CAPACITANCE VALUES ONE AND E-w.-I AS£ OVER IN PICOFARADS. LESS EXPLAINED ON SEPARATE SHEET 0 "' SUPPLIED IN INSTRUCTION BOOK THAN ONE IN MICROFARADS. 7. KNOB CONTROL COLL 3. 'AEFER'TO SERVICE NOTES IN INSTRUC 0 Q/01 Q/04-Q/07 Q/02 Q/03 TION BOOK FOR VOLTAGES 8. (9 SCREWDRIVER CONTROL APPEARING ON DIAGRAM 9. AT ANCHOR TERMINAL 4. RESISTORS 114 WAIT 10. TP . TEST POINT ------~10~ • Value determined at factory.

R/37 !OK

R/30 R/11 R/18 3.3K 9/K /OK A.T./04

R/32 A.r. 20K ~ C/18 R/33 5pF rw~~. 5--2~ --...~----f_' __ol, OUTPUT 2.7K R/:16 - CRIQ3 300K - I/2W Q/06 A.T. + R/20 C/21 + 106 91 0.68 ..... + R/21 + (I 15K C/23 R/22 C/14 270 5/K CI/7T 1 40pF 1.5pF - A.T. R/.!5 GN i f09 lOOK II t 'I C/16 A .b"1'- I 5}/F II I I II R/28 A.T./08 II 332 II A. r. 1/BW A.T./2? II 125 II A.T.Ie4 20?r 206F //IF 112r I02r J.r. ::;t."--T.I/5 OFF ~-~ • R/27 A.T.I/9 IO.Jr CF 2.55K • I/8W Cs 204R·---... R/29 300K • BF • • Bs /!OF • AF • • AI 112F • BAT • • Sf02 S/01 S/02 S/02

1\ "\oro r [\,. 0 \ I I 0 t<,. \ I II.

o"' B)~;..zo.Jr lo A.T./28 ,_0[@3~.T.I06 \ .--"\ .,.. St~l --f o S/02 I • o 204R.. -AI II 0 o~ -~A.T./29 ~; , -...,'' ....J oj l)\"-"'2:5FioA.T./30 "' I \ 'y J ~ 20rr \_t 206r A.r. \/ r A.T./24 121