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Audio Systems Guide for HOUSES OF WORSHIP 7 CHAPTER TWO THE SOUND SOURCE The sound sourcesmost often found in worship facility applications are the speaking voice the singing voice and a variety of musical instruments Voices may be male or female loud or soft single or multiple close or distant etc Instruments may range from a simple
Audio Systems Guide for,Ta b l e o f C o n t e n t s HOUSES OF WORSHIP. Introduction 4 Chapter 8,Typical Applications 36,Chapter 1 Lectern 36. Sound 5 Altar 37,Handheld Vocal 38,Chapter 2 Lavalier 39. The Sound Source 7 Headworn 40,Chapter 3 Congregation 43. The Sound System 8 Musical Instruments 43, What is good sound 9 Non Sanctuary Applications 45. Chapter 4 Glossary 47,Microphones Characteristics Selection 10. Appendix One,Chapter 5 The Decibel 50,Microphones Use 17. Interference Effects 19 Appendix Two,Microphone Hookup 21 Potential Acoustic Gain 51. Chapter 6 Appendix Three, Wireless Microphone Systems 25 Stereo Microphone Techniques 53. Other Wireless Systems 30,Conclusion 54, Automatic Microphone Systems and Signal Processors 32 Bibliography 55. Signal Processors,Equalizers and Feedback Control 33 Biography 55. Shure Products Selection Chart 56,Houses of Worship. Audio Systems Guide for,HOUSES OF WORSHIP,Introduction. Audio systems for house of worship applications The scope of this guide is limited primarily to the. have evolved from simple speech reinforcement selection and application of microphones. to full concert quality multi media systems for house of worship applications Since the. They run the gamut from the most traditional microphone is the interface between the sound. services to the most contemporary services and source and the sound system it is necessary to. nearly every combination in between Recording include some discussion of these two subjects. broadcast and video production are additional and the subject of sound itself to properly. aspects that must often be integrated with the understand the function of the microphone. audio system In addition certain related devices such as. wireless microphones automatic mixers and, Though analog sound systems are still appropriate audio signal processors will be discussed. in many small and medium size applications Large scale mixers power amplifiers and. digital technology can now be found in nearly loudspeakers are left to other publications. every sound system component Digital mixers, signal processors and networking are standard The objective of this guide is to provide the reader. in most medium and large sound systems with sufficient information to successfully choose. Though the basic transducer microphone and and use microphones and related equipment in a. loudspeaker remains in the analog domain variety of typical house of worship applications. even those components are now paired with However for design and installation of a complete. technology such as digital wireless microphone audio system the interested reader is encouraged. system or a digital loudspeaker control system to consult a qualified audio professional. However no matter how complex the overall audio,system an understanding of the basic principles. of sound the key elements of sound systems and,the primary goal of good sound will insure the. best results in choosing and using that system,Introduction. Audio Systems Guide for,HOUSES OF WORSHIP, C H A P TE R ONE The amplitude of a sound wave refers to the. magnitude strength of the pressure changes and, SOUND determines the loudness of the sound Amplitude is. measured in decibels dB of sound pressure level SPL. Because good sound quality is the goal of any house and ranges from 0 dB SPL the threshold of hearing to. of worship sound system it is helpful to be familiar with above 120 dB SPL the threshold of pain The level of. some general aspects of sound how it is produced conversational speech is about 70dB SPL A change of 1. transmitted and received In addition it is also useful to dB is about the smallest SPL difference that the human ear. describe or classify sound according to its acoustic can detect while 3 dB is a generally noticeable step and. behavior Finally the characteristics of good sound an increase of 10 dB is perceived as a doubling of. should be understood loudness See Appendix One The Decibel. Sound is produced by vibrating objects These,include musical instruments loudspeakers and of. course human vocal cords The mechanical vibrations. of these objects move the air which is immediately. adjacent to them alternately pushing and pulling the. air from its resting state Each back and forth vibration. produces a corresponding pressure increase,compression and pressure decrease rarefaction in. the air A complete pressure change or cycle occurs. when the air pressure goes from rest to maximum to. minimum and back to rest again These cyclic pressure. changes travel outward from the vibrating object forming. a pattern called a sound wave A sound wave is a series. of pressure changes cycles moving through the air,A simple sound wave can be described by its. frequency and by its amplitude The frequency of a sound. wave is the rate at which the pressure changes occur It is Instrument Frequency Ranges. measured in Hertz Hz where 1 Hz is equal to 1 cycle per. second The range of frequencies audible to the human ear Another characteristic of a sound wave related to. extends from a low of about 20 Hz to a high of about frequency is wavelength The wavelength of a sound wave. 20 000 Hz In practice a sound source such as a voice is the physical distance from the start of one cycle to the. usually produces start of the next cycle as the wave moves through the air. many frequencies Since each cycle is the same the distance from any point. simultaneously In in one cycle to the same point in the next cycle is also one. any such complex wavelength for example the distance from one maximum. sound the lowest pressure point to the next maximum pressure point. 0 AMPLITUDE frequency is called Wavelength is related to. the fundamental frequency by the speed,DISTANCE WAVELENGTH. and is responsible of sound The speed of, Schematic of Sound Wave for the pitch of the sound is the velocity at. sound The higher which a sound wave travels, frequencies are called harmonics and are responsible The speed of sound is. for the timbre or tone of the sound Harmonics allow us constant and is equal to. to distinguish one source from another such as a piano about 1130 feet per second. from a guitar even when they are playing the same in air It does not change. fundamental note In the following chart the solid with frequency or wavelength. section of each line indicates the range of fundamental but it is related to them. frequencies and the shaded section represents the in the following way the. range of the highest harmonics or overtones of the frequency of a sound Sound Pressure Level of. instrument multiplied by its wavelength Typical Sources. Audio Systems Guide for,HOUSES OF WORSHIP, be delayed relative to the direct sound There are several. kinds of indirect sound depending on the acoustic,space room acoustics. Echo occurs when an indirect sound is delayed long. enough by a distant reflecting surface to be heard by the. listener as a distinct repetition of the direct sound If indirect. sound is reflected many times from different surfaces it. becomes diffuse or non directional This is called, reverberation and it is responsible for our auditory. perception of the size of a room Reverberant sound is a. major component of ambient sound which may include. Wave Equation other non directional sounds such as wind noise or. building vibrations A certain amount of reverberant sound. always equals the speed of sound Thus the higher the is desirable to add a sense of space to the sound but an. frequency of sound the shorter the wavelength and the excess tends to make the sound muddy and unintelligible. lower the frequency the longer the wavelength The One additional form of indirect sound is known as. wavelength of sound is responsible for many acoustic effects a standing wave This may occur when the wavelength of. After it is produced sound is transmitted through a a sound is the same distance as some major dimension. medium Air is the typical medium but sound can also of a room such as the distance between two opposite. be transmitted through solid or liquid materials Generally walls If both surfaces are acoustically reflective the. a sound wave will move in a straight line unless it is frequency corresponding. absorbed or reflected by physical surfaces or objects in its to that wavelength will be Indirect. path However the transmission of the sound wave will be amplified by addition of Sound Path. affected only if the size of the surface or object is large the incoming and outgoing. compared to the wavelength of the sound If the surface is waves resulting in a Direct. small compared to the wavelength the sound will proceed strong stationary wave Source. as if the object were not there High frequencies short pattern between the two Direct vs Indirect Sound. wavelengths can be reflected or absorbed by small surfaces This happens. surfaces but low frequencies long wavelengths can be primarily with low frequencies which have long. reflected or absorbed only by very large surfaces or objects wavelengths and are not easily absorbed. For this reason it is easier to control high frequencies by A very important property of direct sound is that it. acoustic means while low frequency control requires becomes weaker as it travels away from the sound source at. massive and expensive techniques a rate governed by the inverse square law For example. Once a sound has been produced and transmitted it is when the distance increases by a factor of two doubles the. received by the ear and of course by microphones In the sound level decreases by a factor of four the square of two. ear the arriving pressure changes push and pull on the This results in a drop of 6 dB in sound pressure level SPL. eardrum The resulting motion of the eardrum is converted a substantial decrease Likewise when the distance to the. by the inner ear to nerve signals that are ultimately perceived direct sound source is divided by two cut in half the sound. as sound In a microphone the pressure changes act on a level increases by 6 dB In contrast ambient sound such as. diaphragm The resulting diaphragm motion is converted by reverberation has a relatively constant level Therefore at a. one of several mechanisms into electrical signals which are given distance from a sound source a listener or a. sent to the sound system For both receivers the sound microphone will pick up a certain proportion of direct. picked up is a combination of all pressure changes occurring sound vs ambient sound As the. just at the surface of the eardrum or diaphragm distance increases the direct. Sound can be classified by its acoustic behavior for sound level decreases while the. example direct sound vs indirect sound Direct sound ambient sound level stays the. travels from the sound source to the listener in a straight same A properly designed sound 1. line the shortest path Indirect sound is reflected by one system should increase the. or more surfaces before reaching the listener a longer amount of direct sound reaching. 52 58 64 70 76db, path Since sound travels at a constant speed it takes a the listener without increasing the. longer time for the indirect sound to arrive and it is said to ambient sound significantly Inverse Square Law. Audio Systems Guide for,HOUSES OF WORSHIP,C H A P TE R TW O. THE SOUND SOURCE, The sound sources most often found in worship The acoustics of the room are often as important as the. facility applications are the speaking voice the singing sound source itself Room acoustics are a function of the. voice and a variety of musical instruments Voices may size and shape of the room the materials covering the. be male or female loud or soft single or multiple close or interior surfaces and even the presence of the. distant etc Instruments may range from a simple congregation The acoustic nature of an area may have a. acoustic guitar to a pipe organ or even to a full orchestra positive or a negative effect on the sound produced by. Pre recorded accompaniment is also very common voices instruments and loudspeakers before it is picked. In addition to these desired sound sources there are up by microphones or heard by listeners absorbing or. certain undesired sound sources that may be present diminishing some sounds while reflecting or reinforcing. building noise from air conditioning or buzzing light other sounds Strong reflections can contribute to. fixtures noise from the congregation sounds from street undesired sound in the form of echo standing waves or. or air traffic etc Even some desired sounds may become excessive reverberation. a problem such as an organ that overpowers the choir Thus sound sources may be categorized as desired. In this context the loudspeakers of the sound system or undesired and the sound produced by them may be. must also be considered a sound source They are a further classified as being direct or indirect In practice. desired sound source for the congregation but they can the soundfield or total sound in a space will always consist. become an undesired source for microphone pickup of both direct and indirect sound except in anechoic. feedback an annoying howl or ringing sound can occur chambers or to some extent outdoors when there are no. in a sound system if microphones hear too much of the nearby reflective surfaces. loudspeakers,Loudspeaker Loudspeaker,direct sound Singers direct sound. Direct Sound,Sound Field,Inside Noise Outside Noise. e g air conditioning e g street noise,Reflected Sound. Sound Sources and Sound Field,Audio Systems Guide for. HOUSES OF WORSHIP, C H A P TE R THREE function of these processors is to enhance the sound in some. way or to compensate for certain deficiencies in the sound. THE SOUND SYSTEM sources or in the room acoustics, In addition to feeding loudspeakers an output of the. A basic sound reinforcement system consists of an system may be sent simultaneously to recording devices or. input device microphone a control device mixer an even used for broadcast It is also possible to deliver sound. amplification device power amplifier and an output to multiple rooms such as vestibules and cry rooms by. device loudspeaker This arrangement of components is using additional power amplifiers and loudspeakers. sometimes referred to as the audio chain each device is Finally it may be useful to consider the room. linked to the next in a specific order The primary goal of acoustics as part of the sound system acoustics act as a. the sound system in house of worship sound applications signal processor that affects sound both before it is. is to deliver clear intelligible speech and usually picked up by the microphone and after it is produced by. high quality musical sound to the entire congregation the loudspeakers Good acoustics may enhance the. The overall design and each component of it must be sound while poor acoustics may degrade it sometimes. intelligently thought out carefully installed and properly beyond the corrective capabilities of the equipment. operated to accomplish this goal In any case the role of room acoustics in sound system. There are three levels of electrical signals in a sound performance cannot be ignored. system microphone level a few thousandths of a Volt. line level approximately one Volt and speaker level ten. Volts or higher See Appendix One The Decibel What is good sound. Sound is picked up and converted into an electrical The three primary measures of sound quality are. signal by the microphone This microphone level signal is fidelity intelligibility and loudness In a house of worship the. amplified to line level and possibly combined with signals quality of sound will depend on the quality of the sound. from other microphones by the mixer The power amplifier sources the sound system and the room acoustics. then boosts the line level signal to speaker level to drive Typically our references for sound quality are high fidelity. the loudspeakers which convert the electrical signal back music systems broadcast television and radio motion. into sound picture theaters concerts plays and everyday. Electronic signal processors such as equalizers limiters conversation To the extent that the quality of many of these. or time delays are inserted into the audio chain usually references has improved dramatically over time our. between the mixer and the power amplifier or often within expectations of the sound quality in worship facilities has. the mixer itself They operate at line level The general also increased. Typical Sound System,Audio Systems Guide for,HOUSES OF WORSHIP. The fidelity of sound is primarily determined by the aimed toward the listener and away from walls and other. overall frequency response of the sound arriving at the reflective surfaces that contribute to reverberation Again. listener s ear It must have sufficient frequency range and directional control is more easily achieved at high. uniformity to produce realistic and accurate speech and frequencies than at low frequencies. music All parts of the audio chain contribute to this a Finally the loudness of the speech or music at the. limitation in any individual component will limit the fidelity furthest listener must be sufficient to achieve the required. of the entire system Frequency range of the human voice effect comfortable levels for speech perhaps more. is about 100 12kHz while a compact disc has a range of powerful levels for certain types of music These levels. 20 20kHz A telephone has a frequency range of about should be attainable without distortion or feedback The. 300 3kHz and though this may be adequate for con loudness is determined by the dynamic range of the. versational speech it would certainly be unacceptable for sound system the potential acoustic gain PAG of the. a sound system However even a high fidelity source system and the room acoustics The dynamic range of a. reproduced through a high fidelity sound system may sound system is the difference in level between the noise. suffer due to room acoustics that cause severe frequency floor of the system and the loudest sound level that it can. imbalances such as standing waves produce without distortion It is ultimately limited only by. The intelligibility of sound is determined by the overall the available amplifier power and loudspeaker efficiency. signal to noise ratio and the direct to reverberant sound The loudness requirement dictates the needed acoustic. ratio at the listener s ear In a house of worship the primary gain NAG so that the furthest listener can hear at a level. signal is the spoken word The noise is the ambient similar to closer listeners It is relatively easy to design a. noise in the room as well as any electrical noise added by playback only system with adequate dynamic range. the sound system In order to understand speech with based only on NAG and component specifications. maximum intelligibility and minimum effort the speech However a sound reinforcement system with micro. level should be at least 20dB louder than the noise at every phones requires consideration of potential acoustic gain. listener s ear The sound that comes from the system Potential Acoustic Gain PAG is a measure of how. loudspeakers already has a signal to noise ratio limited by much gain or amplification a sound system will provide. the speech to noise ratio at the microphone To insure that before feedback occurs This turns out to be much more. the final speech to noise ratio at the listener is at least difficult than designing for dynamic range because it. 20dB the speech to noise ratio at the microphone must be depends very little on the type of system components but. at least 30dB That is the level of the voice picked up by very much on the relative locations of microphones. the microphone must be at least 30dB louder than the loudspeakers talkers and listeners See Appendix Two. ambient noise picked up by the microphone Potential Acoustic Gain. The direct to reverberant ratio is determined by the Room acoustics also play a role in loudness. directivity of the system loudspeakers and the acoustic Specifically reverberant sound adds to the level of the. reverberation characteristic of the room Reverberation overall soundfield indoors If reverberation is moderate the. time is the length of time that a sound persists in a room loudness will be somewhat increased without ill effect If. even after the sound source has stopped A high level of reverberation is excessive the loudness may substantially. reverberant sound interferes with intelligibility by making it increase but with potential loss of fidelity and intelligibility. difficult to distinguish the end of one word from the start of Although good sound is qualitatively determined. the next A reverberation time of 1 second or less is ideal for by the ear of the beholder there are quantitative design. speech intelligibility However such rooms tend to sound methods and measurements that can be used to. somewhat lifeless for music especially traditional choral or accurately predict and evaluate performance It is. orchestral music Reverberation times of 3 4 seconds or usually possible though often not easy to resolve the. longer are preferred for those sources competing factors of acoustics sound systems. Reverberation can be reduced only by absorptive architecture aesthetics and budget in order to deliver. acoustic treatment If it is not possible to absorb the good sound in a house of worship However major. reverberant sound once it is created then it is necessary deficiencies in any of these areas can seriously. either to increase the level of the direct sound to decrease compromise the final result Readers who are. the creation of reverberant sound or a combination of the contemplating major sound system purchases acoustic. two Simply raising the level of the sound system will raise changes or new construction are encouraged to speak. the reverberation level as well However use of directional with knowledgeable consultants and or experienced. loudspeakers allows the sound to be more precisely contractors to ensure the best sound. Audio Systems Guide for,HOUSES OF WORSHIP, C H A P TE R FOUR systems or are of historical interest only They are rarely. encountered in worship facility sound applications. MICROPHONES Dynamic microphones employ a diaphragm voice. CHARACTERISTICS SELECTION coil magnet assembly which forms a miniature sound. driven electrical generator Sound waves strike a thin. The microphone is the first link in the audio chain plastic membrane diaphragm which vibrates in. and is therefore critical to the overall performance of a response A small coil of wire voice coil is attached to. sound system Improper selection of microphones may the rear of the diaphragm and vibrates with it The voice. prevent the rest of the system from functioning to its full coil itself is surrounded by a magnetic field created by a. potential Proper selection of microphones depends on small permanent magnet It is the motion of the voice. an understanding of basic microphone characteristics coil in this magnetic field which generates the electrical. and on a knowledge of the intended application signal corresponding to the sound picked up by a. To be most effective a microphone must be matched dynamic microphone. both to the desired sound source voice musical Dynamic microphones have relatively simple. instrument etc and to the sound system PA system construction and are therefore economical and rugged. tape recorder etc with which it is used There are five They are not affected by extremes of temperature or. areas of microphone characteristics that must be humidity and they can handle the highest sound. considered when selecting a microphone for a particular pressure levels without overload However the. application They are 1 the operating principle of frequency response and sensitivity of a dynamic. the microphone 2 the frequency response of the microphone is somewhat limited particularly at very. microphone 3 the directionality of the microphone high frequencies In addition they cannot be made very. 4 the electrical output of the microphone and small without losing sensitivity Nevertheless dynamic. 5 the physical design of the microphone microphones are the type most widely used in general. sound reinforcement and have many applications in,worship facility sound systems. 1 Operating Principle How does the microphone Condenser microphones are based on an. change sound into an electrical signal electrically charged diaphragm backplate assembly. which forms a sound sensitive capacitor Here sound. The operating principle describes the type of waves vibrate a very thin metal or metal coated plastic. transducer inside the microphone A transducer is a diaphragm The diaphragm is mounted just in front of a. device that changes energy from one form into another in rigid backplate metal or metal coated ceramic In. this case acoustic energy into electrical energy It is the electrical terms this assembly or element is known as a. part of the microphone that actually picks up sound and capacitor historically called a condenser which has. converts it into an electrical signal The operating principle the ability to store a charge or voltage When the element. determines some of the basic capabilities of the is charged an electric field is created between the. microphone diaphragm and the backplate proportional to the spacing. The two most common types are dynamic and between them It is the variation of this spacing due to. condenser Although there are other operating principles the motion of the diaphragm relative to the backplate that. used in microphones such as ribbon crystal carbon produces the electrical signal corresponding to the sound. etc these are used primarily in communications picked up by a condenser microphone. 10 Dynamic Microphone Condenser Microphone,Audio Systems Guide for. HOUSES OF WORSHIP, The construction of a condenser microphone must The two general types of frequency response are. include some provision for maintaining the electrical flat and shaped These terms refer to the graphical. charge An electret condenser microphone has a representation of frequency response or response curve. permanent charge maintained by a special material A microphone that provides a uniform output at every. such as Teflon deposited on the backplate or on the audible frequency is represented on a frequency. diaphragm Other types are charged by means of an response graph as an even flat line and is said to have. external power source a flat response This means that the microphone. All condenser microphones contain additional reproduces all of the sound within its frequency range. circuitry to match the electrical output of the element with little or no variation from the original sound In. to typical microphone inputs This requires that all addition flat response microphones typically have an. condenser microphones be powered either by batteries or extended frequency range that is they can reproduce. by phantom power a method of supplying power to a very high and or very low frequencies as well Wide range. microphone through the microphone cable itself There flat response microphones have a natural high fidelity. are two potential limitations of condenser microphones uncolored sound. due to the additional circuitry first the electronics. produce a small amount of noise second there is a limit. to the maximum signal level that the electronics can. handle Good designs however have very low noise levels. and are also capable of very wide dynamic range,Condenser microphones are more complex than. dynamics and tend to be somewhat more costly, However condensers can readily be made with higher. sensitivity and can provide a smoother more natural. sound particularly at high frequencies Flat frequency. response and extended frequency range are much easier. to obtain in a condenser In addition condenser Flat Frequency Response. microphones can be made very small without significant. loss of performance By contrast a shaped microphone response will. The decision to use a condenser or dynamic appear on a frequency response graph as a varying line. microphone depends not only on the sound source and with specific peaks and dips This shows that the. the signal destination but on the physical setting as well microphone is more sensitive to certain frequencies than. From a practical standpoint if the microphone will be to others and often has a limited frequency range. used in a severe environment such as a fellowship hall or A shaped response is usually designed to enhance the. for outdoor sound a dynamic microphone would be a sound of a particular source in a particular application. good choice In a more controlled environment for while at the same time minimizing the pickup of certain. example in a sanctuary auditorium or theatrical setting unwanted sounds Shaped response microphones each. a condenser microphone might be preferred for some have a characteristic sound. sound sources especially when the highest sound quality. is desired,2 Frequency Response How does the microphone. The frequency response of a microphone is defined by. the range of sound from lowest to highest frequency that. it can reproduce and by its variation in output within that. range It is the frequency response that determines the. basic sound of the microphone,Shaped Frequency Response. Audio Systems Guide for,HOUSES OF WORSHIP, The selection of a flat or shaped response microphone to different applications Most common are. microphone involves consideration of both the sound low frequency rolloff controls which can help prevent. source and the sound destination The frequency range of rumble and presence rise switches to enhance. the microphone must be wide enough to pick up the intelligibility. desired range of the sound source This range must also. be appropriate to the intended destination of the sound. that is wider range for high quality sound systems or 3 Directionality How does the microphone respond to. recording broadcast systems narrower range for speech sound from different directions. only public address systems, Within its range the microphone should respond in The directional characteristic of a microphone is. such a way that the sound is reproduced either with no defined as the variation of its output when it is oriented at. change flat response or with changes that enhance the different angles to the direction of the sound It. sound in some desirable manner shaped response determines how best to place the microphone relative to. Normally microphones with flat wide range response are the sound source s in order to enhance pickup of. recommended for high quality pickup of acoustic desired sound and to minimize pickup of undesired. instruments choral groups and orchestras especially sound The polar pattern of a microphone is the graphical. when they must be placed at some distance from the representation of its directionality The two most common. sound source Flat response microphones are less prone directional types are omnidirectional and unidirectional. to feedback in high gain distant pickup applications A microphone that exhibits the same output. because they do not have frequency response peaks that regardless of its orientation to the sound source will show. might trigger feedback at any specific frequency on a polar graph as a smooth circle and is said to have. The most common shaped response is for vocal use an omnidirectional pattern This indicates that the. Typically this consists of limiting the range to that of the microphone is equally sensitive to sound coming from all. human voice and adding an upper mid range response directions An omnidirectional microphone can therefore. rise Such a presence rise coupled with controlled low pick up sound from a wide area but cannot be aimed. and high frequency response can give a sound with to favor one sound over another. improved vocal clarity This is especially true for lapel or A unidirectional microphone on the other hand is. lavalier microphones The pickup of certain instruments most sensitive to sound coming from only one direction. such as drums and guitar amplifiers may also benefit On a polar graph this will appear as a rounded. from a shaped response microphone but non circular figure The most common type of. Finally the frequency response of some microphones unidirectional microphone is called a cardioid because of. is adjustable typically by means of switches to tailor the its heart shaped polar pattern. Omnidirectional Microphone Cardioid Unidirectional Microphone. Audio Systems Guide for,HOUSES OF WORSHIP, A cardioid type is most sensitive to sound coming projection called a lobe toward the rear of the. from in front of the microphone the bottom of the microphone The direction of least sensitivity null angle. heart On the polar graph this is at 0 degrees or on for these types is about 125 degrees for the supercardioid. axis It is less sensitive to sound reaching the and 110 degrees for the hypercardioid In general any. microphone from the sides off axis and the direction directional pattern that has a narrower front coverage. of least sensitivity is toward the rear the notch at the top angle than a cardioid will have some rear pickup and a. of the heart For any microphone the direction of least different null angle. sensitivity minimum output is called the null angle For. a cardioid pattern this is at 180 degrees or directly behind. the microphone,Thus a unidirectional microphone may be aimed at. a desired direct sound by orienting its axis toward the. sound It may also be aimed away from an undesired, direct sound by orienting its null angle toward the sound. In addition a unidirectional microphone picks up less. ambient sound than an omnidirectional due to its overall. lower sensitivity at the sides and rear For example a. cardioid picks up only one third as much ambient sound Monitor Speaker Placement For Maximum Rejection. as an omnidirectional type Cardioid and Supercardioid. Although the output of a unidirectional microphone is. maximum for sound arriving at an angle of 0 degrees or The significance of these two polar patterns is their. on axis it falls off only slightly for sound arriving from within greater rejection of ambient sound in favor of on axis. a certain angle off axis The total directional range for sound the supercardioid has the maximum ratio of. usable output is called the coverage angle or pickup arc on axis pickup to ambient pickup while the hypercardioid. for a cardioid microphone this is about 130 degrees has the least overall pickup of ambient sound only one. Two related types of unidirectional microphones are quarter as much as an omni These can be useful types. the supercardioid and the hypercardioid Compared to for certain situations such as more distant pickup or in. a cardioid type these have a progressively narrower higher ambient noise levels but they must be placed. coverage angle 115 degrees for a supercardioid and 105 more carefully than a cardioid to get best performance. degrees for a hypercardioid However unlike the cardioid Other types of unidirectional microphones include. they have some pickup directly behind the microphone shotgun and parabolic reflector models The shotgun. This is indicated in their polar patterns by a rounded has an extremely narrow pickup pattern and is used in. very high ambient noise situations However its limited. off axis sound quality makes it unsuitable for typical. religious facility sound reinforcement It is most often used. in broadcast and film production, The parabolic type actually employs an omnidirectional. microphone placed at the focal point of a parabolic reflector. Like a reflecting telescope most of the energy sound. striking the reflector is concentrated at the focal point This. effectively amplifies the sound from a distant source. However poor low frequency response uneven off axis. response and its large size make it also unsuitable for sound. reinforcement Again it is used primarily in broadcast. applications such as sporting events,One additional directional microphone is the. bidirectional type As the name implies it is equally. sensitive to sound from two directions directly in front of. the microphone and directly behind it Its polar graph. Supercardioid Microphone consists of a front pickup area and an identical rear lobe. and resembles a figure 8 pattern Although the front. Audio Systems Guide for,HOUSES OF WORSHIP, coverage angle of a bidirectional microphone is only 90 many voices Omnidirectional microphones do not exhibit. degrees it has equal rear coverage The null angle is at proximity effect In addition omnidirectional microphones. 90 degrees which is directly at the side of the are less sensitive to wind noise and to handling noise. microphone While the bidirectional microphone is not Most quality unidirectional types have effective built in. used by itself in any typical house of worship sound windscreens and shock mounts to compensate. application it is occasionally used in combination with. other types for stereo sound reproduction, It should be noted that this discussion of directionality. assumes that the polar pattern for a microphone is uniform. that is the same shape at all,frequencies In practice this is. not always achieved Most,microphones maintain their. nominal polar pattern over,only a limited range of. frequencies This is the reason,that published polar patterns. include curves measured at Proximity Effect Graph,several frequencies High quality. well designed microphones are Selecting an omnidirectional or unidirectional. Bidirectional Polar Pattern distinguished by the uniformity microphone again depends on the sound source and the. of their polar pattern over a destination of the audio signal For recording but not. wide frequency range and by the similarity of the pattern sound reinforcement of choral groups orchestras or. to the theoretical ideal even the congregation an omnidirectional microphone. may be used to pick up sound from all directions rather. than emphasizing individual voices or instruments, However as part of a sound reinforcement or P A system. an omnidirectional microphone may be more prone to. feedback because it cannot be aimed away from the,loudspeakers See page 34 for more discussion of. A unidirectional model can not only help to isolate one. voice or instrument from other singers or instruments but. can also reject background noise In addition a properly. placed unidirectional microphone can minimize feedback. allowing higher sound reinforcement levels For these. reasons unidirectional microphones far outnumber, omnidirectional microphones in day to day use in almost. all worship facility sound applications,Directional Characteristics. 4 Electrical output How does the microphone output. There are a few operational differences between match the sound system input. omnidirectional and unidirectional microphones A useful. feature of most unidirectional types is proximity effect The electrical output of a microphone is. This refers to the increased low frequency response of a characterized by its sensitivity its impedance and by its. unidirectional microphone when it is placed closer than configuration The same characteristics are used to. 1 or 2 feet to the sound source It becomes most describe microphone inputs in sound systems This. noticeable at very short distances a substantial boost in determines the proper electrical match of a microphone. the bass response at less than 2 inches In particular for to a given sound system. closeup vocal use proximity effect can add fullness and The sensitivity of a microphone is defined as its. warmth to the sound and therefore may be desirable for electrical output level for a certain input sound level The. Audio Systems Guide for,HOUSES OF WORSHIP, greater the sensitivity the higher the electrical output will How a Balanced Input Works. be for the same sound level In general condenser,microphones have higher sensitivity than dynamic. microphones of comparable quality It should be noted. that for weak or distant sound a microphone of high. sensitivity is desirable while loud or closeup sound can be. picked up well by lower sensitivity microphones,Impedance is approximately the output electrical. resistance of the microphone 150 600 ohms for low,impedance low Z 10 000 ohms or more for high. impedance high Z While the majority of microphones. fall into one of these two divisions there are some that. How an Unbalanced Input Works, have switchable impedance selection In any case the. choice of impedance is determined by two factors the. length of cable needed from the microphone to the,microphone input and the rated impedance of the. microphone input,The maximum length of cable that may be used with. a high impedance microphone should be limited to no. more than 20 feet For longer cable lengths the,high frequency response of the microphone will be. progressively diminished Low impedance microphones. on the other hand may be used with cable lengths of Balanced and Unbalanced Cables and Connectors. 1000 feet or more with no loss of quality and are therefore. preferable for most applications Unbalanced High Impedance Since all high quality and. The output configuration of a microphone can be either even most medium quality microphones have a balanced. balanced or unbalanced A balanced output carries the low impedance output this is the recommended type for. signal on two conductors plus shield The signals on each the majority of worship facility sound system applications. conductor are the same level but they are of opposite polarity especially when long cable runs are used. one signal is positive when the other is negative Most. microphone mixers have a balanced or differential input 5 Physical design How does the mechanical and. which is sensitive only to the difference between the two operational design relate to the intended application. signals and ignores any part of the signal that is the same in. each conductor Because of the close proximity of the two Microphones for house of worship sound applications. conductors in a balanced cable any noise or hum picked up include several typical designs handheld user worn. by the cable will be the same level and the same polarity in free standing mounted and boundary or surface. each conductor This common mode noise will be rejected mounted Each is characterized by a particular size. by the balanced input while the original balanced shape or mounting method that lends itself to a specific. microphone signal is unaffected This greatly reduces the manner of use In addition some microphones may be. potential for noise in balanced microphones and cables equipped with special features such as on off switches. An unbalanced output signal is carried on a single that may be desirable for certain situations. conductor plus shield An unbalanced input is sensitive Handheld types are widely used for speech and. to any signal on that conductor Noise or hum that is singing in many areas of worship facility sound Since they. picked up by the cable will be added to the original are usually handled passed from person to person or. microphone signal and will be amplified along with it used while moving about they must have a very effective. by the unbalanced input For this reason unbalanced internal shock mount to prevent pickup of handling noise. microphones and cables can never be recommended for In addition they are often used very close to the mouth. long cable runs or in areas where electrical interference and should therefore be equipped with an effective pop. is a problem filter or windscreen to minimize explosive breath sounds. The two most common microphone output types and Size weight and feel are important considerations for a. mixer input types are Balanced Low Impedance and handheld microphone.