NarNarayan Shashtri Institute Of Technology (Nsit) Microphone and its Types Prepared By:- Marsh-Felix N. Kapadia (130340111012) Nayan V. Nandi (130340111015) Akshay J. Pathak (130340111024) Branch:- EC 5th Sem. Subject:- Audio Video Systems

Outlines:- Introduction Definition Overview of the Microphone Types of Microphone Microphone Polar Patterns Applications

Introduction:- A microphone is a type of transducer. Early microphones were invented for communication purposes. Later modifications were made to design as the microphone was used more in entertainment industry. Different situations call for the need of different microphone designs as well different pickup patterns. Need to consider factors such as the source, the location of the source and the environment of the source.

Definitions:- Microphone is a transducer which detects sound signals and produces an electrical image of the sound, i.e. it produces a voltage or a current which is proportional to the sound signal, in other words it converts acoustical energy into electrical energy.

Overview of the Microphone:- Diaphragm—part of microphone which receives the vibration from sound waves. Thickness and material of diaphragm are changed depending on the sound waves you wish to pick up. How it works? Electrical circuit is used to change these detected vibrations into an electrical signal that “images” the sound with an output voltage or current.

Types of Microphone:- The three main types of microphones (according to their principles of operation) are: Dynamic Microphone (Moving Coil Microphone) Condenser Microphone (Capacitor Microphone) Ribbon Microphone

Dynamic Microphone:-

They operate on a magnetic principle : movement of a copper coil around a magnet causes a changing flow of electrons that represent the sound wave. Example: Shure SM 57

Dynamic/Moving Coil microphones Advantages:- Durable and can withstand a lot of volume before they distort (within their own circuitry). They don’t require phantom power to operate. Covers the sound in range between 5-10khz, this adds clarity, presence and understandability to many vocal and instrument sounds. Doesn’t feedback as easily as other mics.

Dynamic/Moving Coil microphones disadvantage:- These microphones often miss the many subtle nuances of sounds because it takes a lot of sound pressure to move the coil.

Dynamic/Moving Coil microphones typical uses:- Mostly live situations, but they are also used a lot in the studio. Close mic applications (1-12 inches). Snare drums, guitar amplifiers, kick drum, vocals and any instrument that can play loud.

Condenser Microphone:-

A charged electrical current is applied to a metal-coated piece of plastic. the coating vibrates sympathetically in response to a sound wave because it is very thin. The metal-coated piece of plastic is positioned close to a piece of metallic alloy. The changes in the space between the surfaces create a changing discharge of electrical current. It makes an electrical version of acoustic energy from the sound source. Example: Audio Technica AT 4033

Condenser/Capacitor microphones advantages:- They respond to fast attacks and transients more precisely than other mics and add little tonal colouration. They can be used to record sounds from a greater distance and capture a broader range of frequencies. Big Advantage: These mics record a sound while capturing natural ambience of a room.

Condenser/Capacitor microphones disadvantages:- Fairly fragile. Feedback too easily in a live environment (although some have low frequency roll off switches to help alleviate feedback frequencies). Require phantom power to operate.

Condenser/Capacitor microphones typical uses:- Recording studios. Can be used to record almost any sound…except very loud ones (ex. Kick drum). Extremely effective with quiet sounds The perfect choice for capturing room ambience. Almost always used for vocals , acoustic guitars and drum ovreheads.

Ribbon Microphone:-

A metallic ribbon is suspended between two poles of a magnet A metallic ribbon is suspended between two poles of a magnet. Sound waves vibrate the metallic ribbon which causes a varying flow of electrons to the different poles of the magnet. Example: Beyer M 160.

Ribbon microphones advantages:- These microphones capture a warmer and smoother sound than dynamic/moving coil microphones. Don’t feedback much in live situations. Don’t require phantom power to operate.

Ribbon microphones disadvantages:- Colours the sound by adding a high frequency edge. Fragile Will only pick up sounds that are very close.

Ribbon microphones typical uses:- Typically used in the studio because they are fragile Used in close mic applications (1-12 inches) Often used for acoustic guitars. Also work well for vocals.

Other Types of Microphone:- Carbon Microphone Electret Microphone Crystal Microphone Fiber-Optic Microphone Laser Microphone Liquid Microphone

Carbon microphone:- Oldest and simplest microphone that uses carbon dust. The technology used in the first  telephones and is still used in some telephones today. The carbon dust has a thin metal or plastic diaphragm on one side.

As sound waves hit the diaphragm, they compress the carbon dust, which changes its resistance. By running a current through the carbon, the changing resistance changes the Amount of current that flows.

ELECTRET Microphone:- Most widely used microphones on Earth. Cheap and relatively simple, electret mics are used in cell phones, computers and hands-free headsets. A type of condenser microphone in which the external charge is replaced with an electret material, which by definition is in a permanent state of electric polarization.

CRYSTAL Microphone:- By attaching a diaphragm to a crystal, the crystal will create signal when sound waves hit the diaphragm.

Directional Characteristics:- A Microphone can be designed to react to: Absolute changes in pressure (i.e. pressure transducer) The difference between pressure at the front and rear of the diaphragm (i.e. pressure gradient), or force & direction of the sound wave (i.e. velocity) This determines its “pickup pattern”.

Microphone Pickup Patterns:- Pickup patterns help to reduce unwanted signal from getting pickups Popular patterns: Monodirectional, Bidirectional, Cardioid, and Omnidirectional.

Omnidirectional Microphones:- Collects sound from all around 360 degrees. A true omni-directional mic is a pure pressure transducer - it strictly measures changes in pressure without any regard to the direction that the wave is traveling. microphone can be share by the group.

Bidirectional Microphones:- Bidirectional = two directions. A true bidirectional mic can be a pressure-gradient or velocity transducer, meaning its response to the sound will depend on the direction the sound wave is coming from. The diaphragm is completely open on both sides so that it can react to pressure changes on either side of the diaphragm This results in a “figure-8” pattern - it is sensitive only to sounds arriving from directly in front or directly behind.

Unidirectional/Cardioid:- Unidirectional = one direction collects most of the sound from the front, and very little from the back and sides. The microphone has a null at 180-degrees - it will not respond to sound approaching directly from the rear. This results in a “heart-shaped” pattern (cardio=heart)

Applications:- Telephones Hearing aids Public address systems for concert halls and public events  Motion picture production Live and recorded audio engineering  Two-way radios Megaphones, radio and television broadcasting In computers for recording voice, speech recognition

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