l)RNAL OF THE
`
`0010 EN61NEERIN6 SOCIETY
`
`l
`
`PEECH ROCESSING
`
`RECORDING TECHNIQUES
`
`AUDIO INSTRUMENTATION
`
`REPRODUCING ELEMENTS
`
`Page 1 of 13
`
`GOOGLE EXHIBIT 1010
`
`

`

`JOURNAL OF THE
`
`AUDIO EN61MEERIN6 SOCIETY
`
`VOLUME 15 NUMBER 4
`
`OCTOBER 1967
`
`ARTICLES
`
`Tone Generation with Multiple Synchronous and Non-Synchronous RC
`Oscillators- Robert E. Owen
`
`366
`
`Acoustical Measurements by Ti me Delay Spectrometry-
`Richard C. Heyser
`.
`
`An Audio Noise Reduction Syi;tem-Ray M. Dolby
`
`Factors Affecting the Needle/ Groove Relationship in .Phonograph
`Playback Systems- C. R . Bastiaans
`.
`
`Sur vey of Methods for MeaSLLring Speech Quality-Michael H. L . Hecker
`.
`and Newman Gurtman
`
`A Comparison of Two Types of D igitized Autocorrelation Vocoders-
`Calvin F. Howard, Harold' J. Manley and James C. Stoddard
`
`Information Content of a Sound Spectrogram-Tiong S11y Y11
`
`A Limited-Vocabulary Adaptiv,e Speech-Recognition System-
`Paul W. R oss
`
`Directional Microphones-Harq F. Olson
`
`A New Concert Violin-Carleen Maley Hutchins and John C. Schelle11g
`
`Miniature Audio Amplifiers-William H. Greenbaum
`
`Sensitivity of Phonograph Turntables to Normal Loads-T. S. Cole, Sr.
`
`DEPARTMENTS
`
`452
`Letters to the Editor
`Obituaries
`464
`Convention Exhibits Preview . 466
`News of the Sections
`472
`Available Literature .
`477
`
`Membership Tnformatfon .
`Sound Track
`Shopping the Audio Market
`Editorial
`Index to Volume 15
`
`370
`
`383
`
`389
`
`400
`
`404
`
`407
`
`414
`
`420
`
`432
`
`438
`
`446
`
`480
`483
`485
`488
`489
`
`EDITORIAL BOARD
`
`Donald M. Black
`Frank A. Comerci
`John D. Colvin
`John M. Hollywood
`Clyde R. Keith
`Earle L. Kent
`
`David L. Klepper
`Doinald S. McCoy
`John G . McKnight
`Jenry B. Minter
`Adolph R. Morgan
`Robert E. Owen
`
`N. C. Pickering
`H. E. Roys
`Robert Schwartz
`Emil P. Vincent
`D. R. von Recklingbausen
`J. G. Woodward
`
`Editor: H arry F. Olson
`Managing Editor: Jacqueline Hmrvcy
`Copy Editor: Elizabeth Braham
`
`Manuscripts, editorial and advert:ising correspondence shou,ld be sent to Editorial
`Offices, Audio Engineering Society Journal, 124 East 40th Street, New York 10016.
`Address all other Society business to the Audio Engineering Society, Room 428,
`Lincoln Building, 60 East 42nd St., New York, N. Y. 10017, Membership informa(cid:173)
`tion and back copies may be obtained from either office.
`
`Journal of the Aud io Engineering Society. Vol ume 15, No. 4, October, 1967. Published quarterly by
`the Audio Engineering Society and sup.pli ed to all members in good standing. Publ ication office,
`104 Liberty Street, Utica, N. Y, 13502, Executive office, Room 428, Lincoln Build ing, 60 East 42nd
`Street, New York, N. Y. 10017. Entered .as second class ma il at the post office at Utica, N. Y. Sub•
`scription to nonmembers, $11 per yea1r. Copyright 1967 by the Audio Engineering Society. The
`Journal is indexed in the Applied Science & Techn ology Index.
`The Journal of the Aud io Engineering Society hereby grants perm ission to reprint in part, any
`paper in th is issue if direct perm ission is obta ined from its author(s) and credit is given to the
`author(s) and thi s journal. An author, or his research affiliate may reproduce his paper in full cred(cid:173)
`iting th is journal. This permission is not assignable,
`The "Journal of t he Audio Engineering' Society" and its cover design has been registered as a
`trademark in the United States Patent Office.
`~ •
`
`OFFICERS 1966-67
`President
`p, R. von Recklinghausen
`e:o:ec11tive Vice-President
`Leo L. Beranek
`Eastem Vice-Preside11t
`Emil P. Vincent
`Ce11/,ral Vice-President
`Jack Behrend
`Jlle,Stern Vice-President
`John P. Jarvis
`Secretary
`John D. Colvin
`Treasurer
`Ralph A. Schlegel
`
`1
`
`BOARD OF GOVERNORS
`John S. Baumann
`Arthur E. Gruber
`Floyd K. Harvey
`David L. Klepper
`Hugh S. Knowles
`Daniel W. Martin
`John T. Mullin
`Rein Narma
`Harry F. Olson
`William H. Thomas
`
`COMMITTEE CHAIRMEN
`Admissions- J. T. Mullin
`Awartls-D. W. Martin
`Convention- 32nd- J. P. Jarvis
`Convcntion- 33rd- E. P. Vincent
`Convention Policy Committee-
`D. W. Martin
`Executive Operating Committee-
`D. R. von Recklinghausen
`Exhibits-J. Harvey
`Finance- R. A. Schlegel
`Historical-I. D. Colvin
`Laws & Resolutions-L. L. Beranek
`I, L. Joel &
`library Committee-
`J, D. Colvin
`Membership- A. E. Gruber
`Nominations- H. S. Knowles
`Publ ications Policy Committee-
`L. L. Beranek
`Sections-0. L. Klepper
`Standards-H. E. Roys
`Sustaining Memberships-
`W. H. Thomas
`
`SECTIONS
`~Pan- Los Angeles-Midwest(cid:173)
`~t" York--San Francisco-
`
`asbington
`
`ADMINISTRATION
`l!xecutive Assistaiit
`b orothy H. Spronck
`
`Page 2 of 13
`
`

`

`Directional Microphones
`
`HARRY F. OLSON
`
`RCA Laboralories, Princeton, New Jersey
`
`A comparison of gradient, end-fired line, and cross-fired surface wave microphones
`has been carried out. The subjects considered include the directivity as a function of
`the dimensions and of frequency, the problem of obtaining a uniform directional pattern
`with respect to frequency, and the ambient noise response and relative pickup distances
`of directional microphones.
`
`INTRODUCTION A directional microphone
`is an
`acousto-electronic
`transducer for converting acoustic
`vibrations into the corresponding electric-al undulations
`which exhibits a variation in response to sounds arriving
`from different directions with respect to some reference
`axis of the system. The main reason for the use of
`directional microphones is to pick up desired sounds and
`discriminate against unwanted sounds such as reverbera(cid:173)
`tion and noise. Directional microphones may be divided
`into two main oategories, namely the gradient types which
`depend for directivity upon the difference in pressure,
`or powers of the difference in pressure, between two
`points in space, and wave types which depend for direc(cid:173)
`tivity upon some form of constructive and destructive
`wave interaction. The purpose of this paper is to describe
`the construction, operation, and performance of gradient
`and wave type directional microphones.
`
`GRADIENT MICROPHONES
`A pressure gradient microphone is a microphone in
`which the electrical output corresponds to a component
`of the gradient or space derivature of the sound ,pressure.
`A first-order pressure gradient microphone is a micro(cid:173)
`phone in which the response corresponds to the difference
`in pressure between two points in space. T he first-order
`pressure gradieut response resembles the particle velocity
`in a sound wave and as a consequence this type of
`microphone is termed a velocity microphone. A first(cid:173)
`order pressure gradient microphone may be depicted as
`consisting of two pressure-sensitive elements separated
`by a distance that is small compared to the wavelength,
`connected in phase opposition as shown in Fig. 1. The
`directional characteristic of a first-order pressure gradient
`microphone is of the cosine type, given by the equation
`( J )
`where e1 = output of the microphone for the angle 0,
`0 = angle between the direction of the incident sound
`and the line joining the two elements, and e0 = output
`of the microphone for 0 = 0. The directional charac(cid:173)
`teristic of the first-order pressure gradient microphone
`is also shown in Fig. 1.
`
`420
`
`A unidirectional microphone is a microphone that
`responds predominantly to sound incident from a single
`solid angle of a hemisphere or Jess. The most common
`
`OUTPUT
`
`Fig. 1, E,lements of a first-order bidirectional gradient
`microphone and corresponding directional characteristic.
`
`unidirectional microphone is the one of gradi.ent type
`in which the directional characteristic is a cardioid. A
`unjdirectional microphone may be depicted as two pres(cid:173)
`sure-sensitive elements separated by a distance that is
`small compared to the wavelength, connected in phase
`opposition through a delay network. The directional
`characteristic oE the first-order gradient unidirectiona l
`microphone is given by the equation
`
`(2)
`where e1 = output of the microphone for the angle 0-
`8 = angle between the direction of the incident sound
`and the line joining the two elements, e,. = output of
`the microphone for 0= 0, D1 = distance between the
`elements, and D2 = path length of the delay. For D 1 =
`D~ the directional characteristic is a cardioid, as shown
`in Fig. 2 . The directional characteristic for '2D~ = D1
`and D2 = 2D 1 are also shown in Fig. 2.
`
`JOURNAL OF THE AUDIO ENGINEERING SOCIETY
`
`Page 3 of 13
`
`

`

`r.
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`
`NEW BRAKING SYSTEM WITH EXCLUSIVE
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`
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`
`$CULLY'S NEW SYNC/MASTER! Remote con(cid:173)
`trol your sync-sessions with Scully's exclusive Sync/
`Master control panel. Ask your Scully distributor about
`th is new optional accessory for our 8-track units.
`
`Scully engineering pioneered the plug(cid:173)
`in head assemblies, plug-in amplifier cards,
`plug-in relays and solid-state electronics.
`
`Now, once again, Scully sets the pace in
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`model 280!
`
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`
`RECORDING INSTRUMENTS COMPANY
`A Division of DICTAPHONE CORPORATION
`
`OCTOBER 1967, VOLUME 15, NUMBER 4
`
`480 aunnell Street
`Bridgeport, Conn. 06607
`(203) 335-5146
`Makers of the renowned Scully lathe, since 1919
`Symbol of Precision in the Recording Industry.
`
`421
`
`Page 4 of 13
`
`

`

`HARRY F. OLSON
`
`PRESSURE
`ELEMENTS
`
`..
`
`.Fig. 2. Elements of a unidirectional gradient microphone and directional characteristics for various ratios of D, and D,.
`
`A second-order pressure gradient unidirectional micro(cid:173)
`phone is depicted in Fig. 3. In this form, the second(cid:173)
`order gradient unidirectional microphone consists of two
`gradient microphones of the first order connected in
`phase opposition combined with a delay line. The direc(cid:173)
`tivity pattern of the second-order gradient unidirectional
`microphone is given by
`e2 = eo(D2 +D 1cos0)cos0
`(3)
`where e2 = output of the microphone for the angle {J,
`() = angle between the direction of the incident sound
`and the line joining tbe two elements, e0 = output of the
`microphone for (} = 0, 0 1 = distance between the two
`first order gradient elements, and D2 = path length of
`the delay.
`The directional characteristics for D 1 = D 2 and 2D2
`= 0 1 are shown in Fig. 3. A consideration of the direc(cid:173)
`tional characteristics of Fig. 3 shows that these are much
`sharper than one Jobe of one of the cosines of Fig. I.
`
`WAVE MICROPHONES
`Line Microphones
`A line microphone is a wave-type directional micro(cid:173)
`phone consisting of a single straight-line element or of
`an array of continuous or spaced electroacoustic trans(cid:173)
`ducing elements disposed on a straight line. In the end(cid:173)
`fired line microphone the maximum response occurs for
`sound a rriving along the axis of the microphone. Typica l
`
`end-fired line microphones are depicted i11 Fig. 4.
`In
`Fig. 4a the line microphone consists of a number of
`small pipes with the open end as pickup points, equally
`spaced on a line, and with rhe other end connected 10
`a transduc ing e lement. In Fig. 4b the line micropbo □e
`consists of a ta pered tllbe connected to rhe l•ransducing
`element.
`.I n Fig. 4c the holes of Fig. 4b a re replaced
`
`TAPPEREO
`PIPE.
`
`TAPERED
`PIPE
`
`PIPES
`
`,;HOLE
`
`SLOT
`
`TRANS.
`ELEMENT
`
`•
`
`TRANS.
`ELEMENT
`
`/
`
`TRANS.
`~LE MENT
`
`/
`
`B
`A
`Fig. 4. D iJferent types of end-fired line microphones. The
`pickup ~yslems are: a. A bundle of different leagtbs of pipe
`with llhe ope.n ends as ,pickup points; b. A tapered pipe with
`holes as pickup points; c. A tapered pipe with a slot as
`pickup point.
`
`C
`
`PRESSURE
`ELEMENTS
`
`o,
`
`O,< Di
`~~
`
`2D1 ' D,
`o•
`1.0
`
`90°
`
`90"
`
`90
`
`90°
`
`180"
`
`180°
`
`OUTPUT
`Fig. 3. Elements of a unidirectional second-order gradient microphone and directional characteristics for two different ra1ioS
`of D, and D,.
`
`422
`
`JOURNAL OF THE AUDIO ENGINEERING soc 1fTY
`
`Page 5 of 13
`
`

`

`This
`is not a
`whispering
`campaign ...
`
`but you might think so. The way word
`has gotten round from one audio en(cid:173)
`gineer to another, one station exec or
`record mogul to another ... about the
`blessed quietness of the new 3M Pro(cid:173)
`fessional Tape Recorder. How it has
`increased signal-to-noise ratio 15 db.
`How our younger generations are the
`equal of anyone else's master. How it
`makes a 10 or more decibel difference
`in noise on your finest LP pressings.
`And you needn't plug in the oscillo(cid:173)
`this difference you can hear!
`scope -
`An ingenious two-track system -
`" Dynatrack" mastering--extends the
`weighted dynamic range of audio tape
`systems to at least 80 db below third
`harmonic distortion. This means, of
`coucse, that our third generation dub
`equals anybody else's master.
`The "Dynatrack" system keeps you
`on a clear track, virtually distortion(cid:173)
`frce. Here's how: a single signal is re(cid:173)
`corded simultaneously on a high or
`"H" track at normal NAB-standard
`level for higher level signals; and on
`a low or "L" track with a pre-empha(cid:173)
`sized response - high frequencies as
`
`OCTOBER 1967, VOLUME 151 NUMBER -4
`
`much as 15 db -
`the better to record
`lower sound level signals.
`On very soft ....---------.
`sounds usually
`lost when re-
`~
`cording at ..._ ___ &~...,...----l
`NAB levels, 1-~--""""-----1
`the l ow track
`puts out a._ ______ _.
`clean, undistorted signal. H owever,
`when the low or "L" track approaches
`distortion, an automatic circuit antici(cid:173)
`pates and switches to the high or "H''
`track - noiselessly and in millisec(cid:173)
`onds. The reserve volume capability
`of the "H" track thereby provides an
`extension of the dynamic range.
`"lsoloop" foils flutter. The unique 3M
`"lsoloop" - virtually an isolated loop
`of tape in the most critical part of the
`recorder -
`is controlled by a di!Ieren(cid:173)
`tial drive capstan that also keeps tape
`loop tension con-
`iNcoiNc
`001c01Nc
`stant. The loop c~~~(':" ms,AN c~~~~:"
`II
`I
`,C?)
`bugs the tape
`heads snugly, and Cir
`isolates the tape
`from the rest of
`the transport.
`The tape path in
`the loop is very
`s hort. U nsu p (cid:173)
`ported tape is re(cid:173)
`duced to 3½ inches. Less tape free
`to shimmy, shake over the heads! Un(cid:173)
`precedented tape support like this con(cid:173)
`siderably lessens flutter rate from that
`in ordinary professional recorders. •
`NAB tapes? Si! Yes, your present pre(cid:173)
`recorded tapes will play, and with new
`brilliance, on the 3M Recorder. And
`you can record standard tapes, to be
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`
`tJ
`
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`
`Plug in 2 new circuit boards to convert
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`linearization for lower distortion.
`Phase correction for cleaner sound.
`Silicon solid-state circuitry. Overdub
`sync is available. M odular e lec(cid:173)
`tronics. Epoxy glass circuit boards.
`Photoelectric tape position sensing.
`Interlock tape safety-go directly from
`"fast forward" or "rewind" to "play."
`Vernier precision editing location and
`marking. Etc. All made-in-America.
`Now offering: Complete console.
`Portable units, complete in two shock(cid:173)
`mounted carrying cases. You may also
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`system, or the " Isoloop" tape trans(cid:173)
`port separately. The coupon will bring
`you a descriptive brochure.
`(NAB Compatibility, too!)
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`•
`
`3M Company, Revere-Mlncom Division
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`Tell me more nbout the new 3M Proressional
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`•
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`Page 6 of 13
`
`

`

`ADM 421
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`ADM 700S
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`-----~-- -
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`
`
`ADM-666
`
`Page 7 of 13
`
`Page 7 of 13
`
`

`

`In use at Pampa Recording. Detroit, Michigan.
`
`from t e smallest component
`T THE
`LA GEST CONSOLE
`need we say more
`
`ANOT 1!11
`SYST MS INNOVATION
`bJ,
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`U 10 DESIGNS
`MANUFACTURING, INC.
`17510 Wyoming Ave., Detroit, Michigan 48221
`
`Page 8 of 13
`
`

`

`by a continuous slot as the pickup line. Construction of
`the lines and transducers is beyond the scope of this paper
`and does not contribute to essential subject matter.
`The directional characteristic of an end-fired Line mi(cid:173)
`crophone is given by
`
`sin[(1r/),) (L-Lcos0)J
`
`(4)
`
`(.,,/).) (L-Lcos(J)
`where e1 = output of the microphone for the angle 0,
`
`e11 = output of the m icrophone for 8 = 0, 8 = angle
`between the direction of the incident sound and the line,
`L = length of the line, and )., = wavelength.
`The directivity characteristics of an end-fired line mi(cid:173)
`crophone are shown in Fig. 5. The directivity is a func(cid:173)
`tion of the length of the line and the frequency.
`
`Surface Microphoifes
`A surface microµhone is a wave-type d irectional micro-
`
`A
`L ENGTH• 4
`
`A
`LENGTH • 2
`
`LENGTH=A
`
`LENGTH= 2A
`
`LENGTH= 4A
`
`LENGTH= 8A
`Cl'
`
`180"
`
`0
`
`O
`
`0
`
`0
`
`0
`
`x-
`
`Fig. 5. Directional characteristics of an end-fired line microphone for various values of the ratio of line length to wave(cid:173)
`length >..
`phone consisting of a surface element or a number of
`transducing elements disposed on a s urface. In the cross(cid:173)
`fired surface m icrophone the maximum sensitivity occurs
`on a line perpendicular to the surface. A cross-fired
`surface microphone consisting of elements approximately
`equally disposed on a circular surface is depicted in Fig.
`6a. The c-ross-fired ciscular s urface may be built as a
`large electroacoustic microphone, as shown in Fig. 6b.
`The directional characteristic of this microphone for
`the front hemisphere may be expressed as
`
`0
`
`0
`
`0 O O
`o O o
`0
`0
`0
`0
`0 oo 0 oo 0
`<!>
`0
`0
`
`0
`
`0
`
`x' X
`
`x'
`
`0 0 0 0 0 0 0 0 0 0
`0
`0 0 0
`O
`0
`0
`O
`
`0
`
`0
`
`0
`
`MICROPHONES \
`
`BACK
`"\:LATE
`
`e.....:..
`
`211 [ ( 1rDO-) sin(IJ
`(1rD/J.)sin0
`
`(5)
`
`where e 1 =
`
`output of the microphone for the angle 0,
`
`SECTION X - X'
`
`SECTION X- X'
`
`A
`Fig. 6. Two types of cross-fired surface microphones. :i,
`A group of microphones located on a smface. b. A condenser
`microphone with the diaphragm as the pickup surface.
`
`B
`
`DIAMETER : ¼
`
`DIAMETER ' }
`
`DIAMETER. ),
`
`DIAMETER' 2>.
`
`Fig. 7. Directional characteristics of a cross-fired surface microphone for various values of the ratio of surface diameter 1o
`wavelength X.
`
`426
`
`JOURNAL OF THE AUDIO ENGINEERI NG soc1En'
`
`Page 9 of 13
`
`

`

`You're looking at a revolutionary
`concept in cardioid microphone design
`- actually two microphones in one.
`It is a microphone system with two
`independent capsules. Like a high(cid:173)
`quality two-way speaker system,
`one capsule responds to low and the
`other to high frequencies with a
`built-in crossover network at 500 cycles.
`
`Go ahead ... pick up the new
`AKG D-200E two-way microphone and
`try it! Then ask your most severe
`critic to listen.
`
`Look for this symbol! It signifies
`this exclusive concept - a product of
`
`AKG research. I
`
`OCTOBER 1967, VOLUME 15, NUMBER 4
`
`427
`
`MICROPHONES•HEADPHONES
`
`O I STRIOUT& O 8Y
`NORTH AMERICAN PHILIPS COMPANY , INC,
`•OO ...... T " 2nd STRE E T. Nl£W YORI(, N l!W YORI( ,oon
`
`Page 10 of 13
`
`

`

`HARRY F. OLSON
`e0 = output of the microphone for 0 = 0, D = diameter
`of the circular surface, 0 = angle between the direction
`of the incident sound and a center line normal to the
`surface, / 1 = Bessel function of the first order, and ). =
`wavelength.
`The exact expression for the directional characteristic
`of the cross-fired circular surface mjcrophone including
`the rear hemisphere is complex and is not presented here.
`The directional characteristics of a cross-fired surface
`microphone are shown in Fig. 7. The directivity is a
`function of the diameter of the surface and of frequency.
`
`COMBINATION LINE AND SURFACE
`MICROPHONE
`
`A combination line and surface microphone is a micro(cid:173)
`phone in which the terminations of a large number of
`line elements are arranged on a circular surface as de(cid:173)
`picted in Fig. 8. The microphone shown in Fig. 8 is one
`form of this combination system.
`The directional char,acteristic of such a microphone is
`the product of an end-fired line and a cross-fired surface.
`The directional characteristics for a combination end(cid:173)
`fired line and cross-fired surface in which length of line is
`three times diameter of the surface are shown in Fig. 9.
`
`COMBINATION LINE AND CARDIOID
`MICROPHONE
`
`A combination line and cardioid microphone is a
`microphone in which a line system is combined with a
`gradient system. One simple form of a combination line
`and cardioid microphone is shown in Fig. 10.
`The directional characteristics of the microphone of
`Fig. IO are shown in Fig. 1 l. J n the low-frequency range
`the directional characteristic is a cardioid because the
`directivity pattern of a short line is practically omni(cid:173)
`d irectional. In the high-frequency range the directivity
`pattern is that of a line microphone.
`
`FRONT VIEW
`
`LINE
`
`LINE
`
`TRANSDUCER
`ELEMENTS
`
`SI DE VIEW
`
`Fig. 8. Front and side views of a combination line a nd
`surface microphone.
`
`LENGTH•-¼>(cid:173)
`
`LENGTH •-fA
`
`DIAMETER•¼
`
`...
`
`DIAMETER•½
`o•
`0
`
`LENGTH• 3A
`
`DIAMETER• A
`
`Fig. 9. Directional characteristics of a combination line
`and surface microphone for various ratios of I ine length and
`surface diameter to wavelength >-. In all cases the line length
`is three times the surface diameter.
`
`NOISE DISCRIMINATION AND RELATIVE
`PICKUP DISTANCE FOR MICROPHONES
`WITH DIFFERENT DIRECTIVITY PATTERNS
`
`The discrimination of a microphone against noise,
`reverberation, and unwanted sounds increases as its di(cid:173)
`rectivity increases. The pickup distance for the same
`
`LINES
`
`L
`
`TRANSDUCER
`EL E,MENTS
`
`OUTPUT
`
`Fig. IO. A combination line and cardioid microphone.
`For a cardioid directivity pattern fo1· the gradient element,
`D,=D,.
`
`reception of noise, reverberation, other unwanted soumls
`increases as directivity of microphone increases.
`The noise-to-signal ratios for various directivity pat·
`terns are shown in F ig. 12. T he r a tio of noise-to-sig nal
`pickup is assumed to be unity for the omnidirectio nal
`m icrophone.
`Figure 12 also shows the pickup distances for the s;1me
`reproduced noise a nd reverberation for various directivity
`patterns. The pickup distanc~ for the omnidirectional
`microphone is assumed to be unity .
`
`CONCLUSIONS
`The directivity characteristics of gradient-type micro·
`phones are essentially invariant with respect to frequency,
`The directivity characteristics of microphones consiSl·
`ing of lines, surfaces, combinations of lines and surfaces,
`
`428
`
`JOURNAL OF THE AUDIO ENGINEERING soc 1ETY
`
`Page 11 of 13
`
`

`

`When Stanton engineers get together,theydrawthe line.
`
`The frequency response curve of the new Stanton 681
`Calibration Standard is virtually a straight line from
`10-20,000 Hz.
`That's a g uarantee.
`In addition, channel separation must be 35 dB or
`greater at 1,000 Hz. Output must be 0.8 mv /cm/sec mini(cid:173)
`mum.
`If a 681 doesn't match these specifications when first
`tested, it's meticulously adjusted until it does.
`Each 681 includes hand-entered specifications that
`verify that your 681 matches the original laboratory stand(cid:173)
`ard in every respect.
`Nothing less would meet the needs of the professional
`studio engineers who use Stanton cartridges as their ref-
`
`erence to approve test pressings. They must hear exactly
`what has been cut into the grooves. No, more. No less.
`But you don't have to be a profe.ssional to hear the
`difference a Stanton 681 Calibration S tandard will make,
`especially with the "Longhair" brush which provides the
`clean grooves so essential for clear reproduction. The im(cid:173)
`provement in performance is immediately audible, even
`to the unpracticed ear.
`The 681 is completely new, from 'its slim-line config-
`uration to the incredibly low-mass moving sys-
`.
`tern. The 681A with conical stylus is SSS..00, the
`· •~ :,,,,_~"
`''~ ~~
`681EE with elliptical stylus, $60.00.
`if(;; ;,,~,:
`For free literature, write to Stanto,n i\llag-
`netics, Inc., Plainview, L. I., N. Y.
`
`Page 12 of 13
`
`

`

`HARRY F. OLSON
`
`UP TO 350Hz
`o•
`,.o
`
`550Hz
`o• ,.o
`
`IIOOHz
`o•
`1,0
`
`2200Hz
`
`4400Hz
`
`Fig. I J. Directional characteristics of a combination line and cardioid microphone for vnrious frequencies. The length
`of the line is 12 in., :ind D, = D,.
`
`and combinations of lines and gradients vary with respect
`to frequency. The net resu lt is frequency discrimination
`for sound sources located off the axis a nd in the reverber(cid:173)
`ant sounds and noise.
`The length of a line must be relati vely great in order
`to obtain some measure of directivity in the low-frequency
`range. For example, the length of an end-fired
`line
`microphone at JOO H z must be 22 ft to equal the direc(cid:173)
`tivity pattern of the second-order gradient m icrophone.
`The obvious conclusion is that a line microphone must
`be very long indeed in order to obtain any semblance of
`d irectivity in t he low-frequency range.
`The diameter of an end-fired surface microphone must
`also be quite large in order to obtain directivity. For
`
`example, at I 00 Hz, the diameter of the end-fired surface
`microphone must be 8 ft in order to equal the directivity
`of the second-order gradient microphone. A disk of this
`diameter is very cu mbersome.
`F o r the combina tion end-fired and cross-fired surface
`mic rophone the length must be 16.5 ft and the diameter
`5.5 ft at 100 Hz LO equal the directivity pattern of the
`second-order gradient microphone. Here again the struc(cid:173)
`ture i
`large and cumbersome.
`ln the case of the combination line and cardioid micro(cid:173)
`phone the directivity in the low-frequency range is that
`of a car dioid. ln general , the range in which directivity
`is most important is the low-frequency range where the
`levels of both ambient noise and reflected sounds are high.
`
`O" ,.o
`
`6
`
`O" ,o
`
`25
`
`5
`
`,eoo
`
`12
`
`35
`
`DIRECTIVITY
`INDEX
`
`DISTANCE
`RATIO
`
`3
`
`I 7
`
`NOISE
`I
`I
`1
`1
`25
`12
`6
`3
`RESPONSE
`Fig. 12. Relation of directivity patterns to the directivity index, disrnnce pickup ratio. and noise response. All
`parameters are assumed to be unity for nondirectional or omnidirectional microphone.
`
`three
`
`THE AUTHOR
`
`H arry F. Olson received the B.S., M .S., Ph.D., and
`E.E. degrees from the University of )owa, and an
`Honorary D.Sc. degree from Iowa Wesleyan College.
`He has been affiliated with the research department of
`Radio Corporation of America. the engineering depart(cid:173)
`ment of RCA Photophone, the research division of
`R CA Manufacturing Company, and RCA Laboratories.
`Dr. Olson is Staff Vice President of the Acoustical and
`E lectromechanical Research Laboratory of the RC A
`Laboratories.
`Dr. Olson, past president of both the Audio Engi(cid:173)
`neering Society and the Acoustical Society of America,
`past chairman of the Administrative Committee lRE
`Professional Gro up on Audio, and currently Editor o(
`the AES Journal, has received the Mo<lcrn Pioneer
`Award of the National Association of Manufacturers,
`John H. Potts Medal of the Audio Engineering Society,
`
`Samuel L. Warner Medal of the Society of Motion Pic(cid:173)
`ture and Television Engineers, John Scoll Medal of the
`C ity of Philadelphia, Achievement Award of the Profes(cid:173)
`sional G roup on Audio of the l'nstitute of Radio Engi(cid:173)
`neers, John Ericsson Medal of the American Society of
`SwecliSh Engineers, Audio Engineering Society Award,
`The Emile Berliner Award and Mervin J . Kelly Award.
`He holds more than 100 U. S. Patents, hHs wrillen
`numerous papers, and books including E lements of
`Acoustic:ll Engineer ing, Acoustical E ngineering, Dy(cid:173)
`nnmic A nalogic.-,. and Musical Engineering.
`A member of Tau Beta Pi. Sigma Xi, and the Na(cid:173)
`tional Academy of Sciences, Dr. Olson is also a Fellow
`of the Society of Motion Picture and Television Engi(cid:173)
`neers, the American Physical Society. the Institute of
`Electrical and Electronics Engineers.
`the Acoustical
`Society of America and an Honorary Member of AES.
`
`430
`
`JOURNAL OF THE AUDIO ENGINEERING SOCIETY
`
`Page 13 of 13
`
`