Microphone Technology - Report Example

Your full full August 16, Microphone Technology Before going into the niceties, let’s first discuss what microphone technology actually is. The technology that utilized devices called microphones to achieve the electroacoustic live transmission of sound the way the speaker or vocalist wants it to be heard just like he hears it himself, is commonly called the microphone technology. It has greatly helped the vocalists to have the right genre of music to be transmitted to the audience, and has also greatly helped the comprehension of sound in noise and crowd for people with hearing loss. For this, we need to understand the basics of this technology that is, what a microphone is and how it works. What is a Microphone? According to Snoman, a microphone, casually referred to as mic or mike, is a device that “converts sound into an electrical current that is then transformed into an audio signal at the end of the chain” (152). How well the sound gets captured by the microphone and un-obstructively reproduced and transmitted to the audience, and how well the microphone meets the live or studio requirements of sound, is the main concern. There is no doubt that when you go for a high quality microphone, you are ultimately ensuring excellence of the sound; however, every microphone has its own tonal quality that is different from other microphones. Thus, choosing the right microphone is what requires good sensible knowledge about the microphone technology and some basic tips and tricks of utilizing this technology. “Microphones are a key factor in achieving high quality recordings and sound reproduction”, says Peterson. The first microphone ever developed consisted of a metal diaphragm connected to a needle which was further connected to a metal foil. When the diaphragm would catch differences in air pressure, it would cause the needle to move which would scratch out specific patterns onto the metal foil. When these scratches were later run by the needle, they would cause the diaphragm to move which reproduced the recorded sound (How Stuff Works). The latest microphone technology, however sophisticated, works on the same principle that is, converting air pressure waves into electrical current. What is the Diaphragm? Whatever the type of the microphone is, all have one thing is common. That is the diaphragm which is actually a thin paper or a thin piece of aluminum or plastic, located in the head of a typical microphone, and vibrates when it catches sound waves produced by differences in air pressure (see Fig. 1). Vibrations in this diaphragm cause vibrations in other modules of the microphone as well which causes them to get converted to electrical signals that are actually the sound that we hear. Classification of Microphones Bore and Peus (9) have classified microphones into three categories depending on their characteristics and functions. These are described below: Passive Transducers All microphones can be referred to as transducers that convert one form of energy (input) into another (output). Microphones that convert acoustical energy directly into electrical signals or the other way round without requiring any peripheral power supply are called passive transducers. The electrical output comes directly from the acoustic power these transducers absorb thus making these “strictly limited by the conservation of energy” (Calvert). Examples include dynamic, magnetic, piezoelectric and dc-polarized condenser microphones. Active Transducers Active transducers produce electric current straight in response to the environmental stimuli and control “an external source of power” (Calvert). Examples include carbon microphones and RF-condenser microphones. Velocity Transducers All magnetic microscopes that operate according to the law of induction are called velocity transducers. Here, the principle is that the output electrical current is proportional to the velocity of the displacement of the diaphragm that occurs as a result of vibrations. Directionality All microphones share one characteristic that is looked for when we have to assess what microphone is best suited for which application. This is called directionality. This tells how much a microphone is sensitive to sound coming from different directions. Some microphones only absorb sound from one direction while some absorb sound coming from all or a combination of directions. Such microphones are called directional microphones. Directionality is of three types (WiseGEEK): Omnidirectional Omnidirectional microphones absorb sound coming from all directions. These are also called pressure transducers. Their front face only is showing to the sound field and the diaphragm tends to pick up all sound vibrations equally that hit its surface no matter which direction they are coming from. Unidirectional Unidirectional microphones absorb sound from one direction only. Bidirectional Bidirectional microphones absorb sound from two dissimilar directions. These are called pressure-gradient transducers as these have special directional properties to look into. Polar Pattern Polar pattern is the name given to the graphical representation of a microphone’s directionality. To help understand this, omnidirectional, cardioid and hyper-cardioid polar patterns are described below. Polar pattern (see Fig. 2) represents the directionality of an omnidirectional transducer which is best suited for situations where the microphone has to remain fixed while the sound source is moving in all directions. Cardioid microphones absorb sound signals in a heart-shaped pattern (more from the front and less from the sides) and that is why it is called cardioid (see Fig. 3). Examples include handheld microphones and those used for general use. Often called shotgun microphones, hyper-cardioid transducers absorb a lot from the sides and back (see Fig. 4). Types of Microphones Microphones are categorized depending upon the technique used by the microphone for the conversion of energy or the application a certain microphone is intended for. Main types are described below: Carbon Microphones These are the oldest microphones that use carbon dust which has a plastic diaphragm connected to one side. When the vibrations of sound touch the surface of the diaphragm, the carbon dust is compressed and its resistance is changed and this controls the electric current flowing through the microphone. Carbon microphones have been used in telephones, radio broadcasting and military installations due to their durability and capacity to perform on low voltage. Dynamic Microphones These belong to the category of velocity transducers. These can easily handle high volumes like musical instruments; and, do not need an external power supply. Since, these are based on the law of induction, “a conducting element is induced to move in a magnetic field by the influence of sound waves. The EMF thus generated is proportional to the velocity of the moving conductor” (Bore and Peus 26). More simply, a wire coil and a magnet are used to create this EMF which creates the audio signals. When the diaphragm, which is connected to the wire coil, receives vibrations, it causes the coil to move to and fro on the magnet. As a result, electric current is generated. These are best suited for general use onstage and by touring instrumentalists and singers because the design is simple and there are fewer components to handle; Ribbon Microphones Ribbon microphones, the velocity transducers, have a thin ribbon that is usually “a strip of aluminum foil a few μm thick” (Bore and Peus 28) suspended in the magnetic field where it vibrates between the poles of the magnet. This ribbon, when moved by the input sound waves, produces electric current. The frequency response in these microphones is free of resonance. Ribbon microphones act as omnidirectional pressure transducers if the ribbon is terminated at its tail by a tube lined with a sound absorptive material producing a force of friction for the ribbon. If a small portion is terminated only instead of the whole of the ribbon, then the cardioid characteristic is introduced in the ribbon microphones. Excellent sound quality of these microphones increases their demand in commercial studios and for recording engineers (Dorrough and Halverson). Condenser Microphones A condenser microphone is a capacitor which is a device that stores energy. The capacitor here would convert the acoustical signals to electricity. One plate of the capacitor moves in response to sound vibrations which changes the capacitance. The changed capacitance is amplified to create electric signals. These are active transducers and thus require an external power supply. Since these are sensitive to high volume, these are best suited for use in studios, “onstage at live music venues for use as drum overheads or for use in orchestral or choral sound reinforcement” (About.com) Crystal/Piezoelectric Microphones In crystal microphones, the diaphragm is attached to a Piezo crystal, the Rochelle Salt. Since crystals have the property of producing EMF when subjected to mechanical stress (called the Piezoelectric effect), thus attaching a diaphragm makes the crystal to produce signals when vibrations hit the diaphragm or when these are deformed. Crystal microphones are used for military and commercial purposes. These are widely used for recording purposes in difficult environments such as underwater due to their high impedance. Conclusion Microphones are widely in use today onstage, in studios and for many other purposes. There are various types of microphones depending upon their sensitivity to high or low volume and kind of applications they are intended for. This paper has discussed the basics of microphone technology and has described the classification and types of microphone, using MLA referencing style. Fig. 1. Microphone Diaphragm Fig. 2 < http://www.mediacollege.com/audio/microphones/directional-characteristics.html> Fig. 3 < http://www.mediacollege.com/audio/microphones/directional-characteristics.html> Fig. 4 < http://www.mediacollege.com/audio/microphones/directional-characteristics.html> Works Cited About.com. “Condenser vs. Dynamic Microphones.” About.com, 2010. Web. 16 Aug. 2010. < http://homerecording.about.com/od/microphones101/a/mic_types.htm >. Bore, Gerhart, and Stephan Peus. “Classification.” Microphones for Studio and Home-Recording Applications. Berlin: Druck-Centrum Fürst GmbH, 1999. Calvert, JB. Microphones. N.p., 31 Aug. 2003. Web. 16 Aug. 2010. . Dorrough, Mike, and Gary Halverson. Five Classic RCA Ribbon Microphones. N.p., 09 Jul. 2001. Web. 16 Aug. 2010. < http://www.coutant.org/ribbons.html >. How Stuff Works. “5 Types of Microphones.” HowStuffWorks, Inc., 2010. Web. 16 Aug. 2010. . Peterson, George. “Microphone Technology 101—Basic Terminology and Techniques for Stage and Studio.” MIX. Penton Media, Inc., 18 May 2004. Web. 16 Aug. 2010. . Snoman, Rick. “Microphone Technology.” Dance Music Manual: Tools, Toys and Techniques. USA: Focal Press, 2009. WiseGEEK. “What is a Directional Microphone?” Conjecture Corporation, 2010. Web. 16 Aug. 2010. . Read More