Microphone types and characteristics
History of the microphone:
Here is a small detailed timeline of history of how the microphone was invented and how it progressed through years. The first person to use the word microphone was Sir Charles Wheatstone in 1827. In 1876, Emile Berliner was the person to invent the first microphone which was used as a voice transmitter, known as a telephone today. He did not invent the telephone, but improved it with the microphone.
By the time 1878 came around, David Edward Hughes invented the carbon microphone which was later developed during the 1920s. With the invention of the radio, new broadcasting microphones also were invented. There would not be a history of microphones if these things did not take place.
James West and Gerhard Sessler of Bell laboratories played a big part in the history of microphones in the year 1964 as they received patent number 3,118,022 for their transducer which is an electric microphone. It offered something previous microphones had not, greater reliability and higher precision with something all consumers loved, a lower price.
This part in the history of microphones revolutionized the industry and made it possible for general consumers to obtain the product. Almost one billion of these microphones were manufactured each year.
Dynamic and condenser microphones were developed in the 1970s because they offer a great amount of sensitivity perfect for broadcasting with. To this day they are used by broadcasters worldwide.
Microphone history dates back to the 1800s so it is possible to see why we have come to such great lengths in offering top of the line, high quality products by many different manufacturers.
How a microphone works:
Here is a diagram that will explain how a microphone converts sound energy into electrical energy. I have labelled each part of the diagram from 1-5 to explain each step of how the microphone works.
- When you speak, sound waves created by your voice carry energy toward the microphone. Remember that sound we can hear is energy carried by vibrations in the air.
- Inside the microphone, the diaphragm (much smaller than you'd find in a loudspeaker and usually made of very thin plastic) moves back and forth when the sound waves hit it.
- The coil, attached to the diaphragm, moves back and forth as well.
- The permanent magnet produces a magnetic field that cuts through the coil. As the coil moves back and forth through the magnetic field, an electric current flows through it.
- The electric current flows out from the microphone to an amplifier or sound recording device. Hey presto, you've converted your original sound into electricity! By using this current to drive sound recording equipment, you can effectively store the sound forever more. Or you could amplify (boost the size of) the current and then feed it into a loudspeaker, turning the electricity back into much louder sound. That's how PA (personal address) systems, electric guitar amplifiers, and rock concert amplifiers work.
Types of microphone:
Dynamic microphone: They work using electromagnetic induction. They can be handled with ease because they are extremely robust and are also relatively cheap to buy. Dynamic microphones are also resistant to moisture.
Capacitor microphone: Capacitor microphones can respond to extremely high audio frequencies. They are usually more sensitive than their dynamic counterparts meaning they require less amplification than dynamic models to produce the same output level from the same signal source. This means quieter or distant sound sources are suited to them better.
Electret condenser: An electret condenser microphone consists of a very light diaphragm (moving plate) and back plate (stationary or static plate) and has a permanent charge implanted in an electret material to provide polarizing voltage. The principle of operation is that sound waves impinging on the diaphragm cause the capacitance between it and the back plate to change synchronously, this in turn induces an AC voltage on the back plate.
1. Foil Electret Condenser Microphone (also called Middle or Classic) - Type of condenser microphone where the electret material is the diaphragm. (Sometimes referred to as "Front" type.)
2. Back Electret Condenser Microphone -Type of condenser microphone where the electret material is the back plate.
3. Front Electret Condenser Microphone -Type of condenser microphone where the electret material is
Ribbon: A Ribbon microphone is a type of microphone that uses thin aluminium, duralumin or sometimes nanofilm ribbon which is placed in-between the poles of a magnet which in turn generates voltages by electromagnetic induction.
Ribbon microphones are standard bidirectional which means that they pick up sounds equally on opposite sides of the microphone for example, the front of the microphone picks up just as well as the back of the microphone would pick it up.
Carbon: The carbon microphone is also known by many as a carbon button microphone, or sometime just a button microphone or a carbon transmitter. A carbon microphone is a sound to electrical signal transducer which consists of two metal plates which are separated by granules of carbon.
One of the plates faces outwards and acts as the diaphragm so that when sound waves strike this plate the pressure on the granules changes which then in turn changes the electrical resistance between the plates. A direct current is then passed from one plate to the other plate which causes the changing resistance to result in changing current which can be used in many ways such as being passed through a telephone system. Before the proliferation of vacuum tube amplifiers in the 1920’s, carbon microphones were the ONLY practical way of obtaining high levelled audio signals.
Crystal: In 1880, Jacques and Pierre Curie discovered the piezoelectric effect. Piezoelectric crystals were first used by Langevin in 1917, in connection with his research efforts in underwater acoustics using ultrasonic transducers. In 1919, using Rochelle Salt, Alexander Nicolson first demonstrated a variety of piezoelectric devices, including loudspeakers, phonograph pickups, and microphones.
Problems in manufacturing crystals with uniformity and the necessary shapes prevented the commercial production of any of these devices. Almost 10 years later, C.B. Sawyer and C.H. Tower developed processes to manufacturer uniform complex-shaped piezo crystals. This led the way for many piezoelectric or crystal transducers, as they were first called.
Problems in manufacturing crystals with uniformity and the necessary shapes prevented the commercial production of any of these devices. Almost 10 years later, C.B. Sawyer and C.H. Tower developed processes to manufacturer uniform complex-shaped piezo crystals. This led the way for many piezoelectric or crystal transducers, as they were first called.
The crystal microphones work on the principal that certain crystals change their electrical properties as they change shape. By attaching a diaphragm to a crystal, the crystal will create a signal when sound waves hit the diaphragm and cause the crystal to deflect.
Lavalier: A Lavalier microphone is a small electret or either dynamic microphone that is used for mainly television purposes in order to be allowed hands free operation. You will most commonly find they have small clips provided with them to attach to collars ties and other clothing. The cord which is connected from the microphone to the radio frequency transmitter is usually hidden underneath clothing of whoever is using the lavalier microphone.
These miniature microphones are usually supplied with a choice of push on grills or differing lengths that provide a gentle high frequency boost for forming a resonant cavity. There is a peak of approximately 6 dB at 6-8 kHz which is considered necessary for compensating loss of clarity when chest mounted. This method of boosting high frequencies does not decrease the noise performance as electronic equalisation would do.
Rifle/ shotgun: Shotgun microphones are the highest directional microphones out of all of them. They have extremely small lobes of sensitivity to the rear, right and left but are significantly less sensitive to the rear and side than most other microphones. This is the result from placing the element at the rear end of a tube with slots cut along the sides.
Wave cancellation eliminates much of the off- axis sound. Due to the narrowness of the sesnsitivity area, Shotgun/ rifle microphones are most commonly used on television in programmes such as news channels where they are interviewing someone live and only want to capture theire voice alone.
Boom microphone: A boom microphone is a directional microphone mounted or attached to a pole or arm. Primarily used in film and television, a boom microphone frees the hands of actors or reporters while allowing them to enjoy the amplified audio of a traditional microphone. Boom microphones can also be used to amplify a group conversation, as it can be positioned so that everyone's voice can be heard.
A boom microphone is simple enough to fashion for amateur productions. A broomstick, microphone stand, or fishing pole can be used to hold the microphone aloft. In fact, on-set, this pole is often called a fish pole. One concern with this type of microphone is vibrations that could mar audio quality. Boom microphones are sensitive enough to pick up such unwanted vibrations as unsteady hands, for example. To prevent this, a boom microphone should include some type of isolating mechanism, such as foam padding or elastic suspensions.
Polar patterns:
An omnidirectional microphone picks up sound equally 360 degrees around the microphone capsule. Omnidirectional microphones sound very open and natural, and are best suited for good acoustic environments or in a recording situation where an open, natural sound is desired.
Omnidirectional microphones can make some of the best recordings of acoustic instruments, given a good recording room. Their natural, open sound also makes binaural recording possible, if mounted properly. Omnidirectional microphones are not preferred for live sound, as they tend to be prone to feedback if amplified, but really shine for recording.
Omnidirectional microphones can make some of the best recordings of acoustic instruments, given a good recording room. Their natural, open sound also makes binaural recording possible, if mounted properly. Omnidirectional microphones are not preferred for live sound, as they tend to be prone to feedback if amplified, but really shine for recording.
A figure-8 (or "bidirectional") microphone picks up sound equally from both sides of the mikes diaphragm. It rejects sound from the sides; as a cardioid pattern would, but picks up sound equally well from the rear as it does the side.
Most ribbon microphones are in figure-8 configurations. Ribbon microphones sound fantastic on acoustic instruments, in stereo configurations for live recording of acoustic and jazz groups, and as drum overheads. Due to their sensitivity, ribbon microphones aren't recommended for harsh, high-SPL environments. Figure-8 microphones are commonly used in "mid-side" recording setups.
Most ribbon microphones are in figure-8 configurations. Ribbon microphones sound fantastic on acoustic instruments, in stereo configurations for live recording of acoustic and jazz groups, and as drum overheads. Due to their sensitivity, ribbon microphones aren't recommended for harsh, high-SPL environments. Figure-8 microphones are commonly used in "mid-side" recording setups.
The most common microphone pickup pattern you'll encounter is the cardioid pattern. Cardioid means "heart-shaped", from the Greek root word "cardi". A cardioid pickup pattern means pickup to the front of the microphone and to a lesser extent the sides, with good rejection of sound to the back of the microphone.
Cardioid microphones are recommended for vocal applications, live taping/recording, and most other situations where the acoustics of the recording environment are good, but not perfect.
Cardioid microphones are recommended for vocal applications, live taping/recording, and most other situations where the acoustics of the recording environment are good, but not perfect.
A hyper cardioid microphone (commonly referred to as "hyper") takes the cardioid concept a step further. A hyper cardioid microphone records from the front, a lesser extent to the sides, and rejects everything around 120 degrees to the back of the microphone. Hyper cardioid microphones work especially well for on-stage vocal applications (to help with monitor feedback) and live recording in far-away or difficult acoustic situations.
Line and Gradient or Shotgun microphones use a complex design that makes their polar pattern highly directional.
The capsule is placed behind an interference tube with small slits along the side. The tube eliminates sound from the sides due to phase cancellation. The longer the interference tube, the tighter the polar pattern, making the microphone better at rejecting sound from the side and more focused in the direction it is pointing.
Shotgun microphones are excellent for film and theatre work to pick up sound while keeping the microphone out of the camera’s view.
Application:
I will now explain what all the purposes of the microphones listed above are for. How they are used for different situations in recording or increasing the volumeincreasing the volume of sound.
Dynamic microphone: Dynamic microphones are principally used as vocal microphones on stage for example like a rock concert or a stand-up comedy in a large packed area. They are also less commonly used in studios such as a radio station for example.
Capacitor microphone: Capacitor microphones are most commonly used for recording studios only and are more suited to this task than Dynamic microphones because the capacitor microphone can change its frequency that means it can handle louder and quieter sounds easier than the dynamic microphone.
Electret condenser: Electret condenser microphones are most commonly used in small devices for communications such as mobile phones and telephones. This is what this type of microphone is most famous for.
Ribbon: Ribbon microphones were commonly used in the 1950’s for recording in studios and doing television broadcasts. These days though, dynamic microphones have taken these purposes from the ribbon microphone. However the Ribbon microphone is still used for different purposes these days such as picking up sounds from stringed instruments and the electric guitar.
Carbon: One of the merits of carbon microphones is that they can actually be used as amplifiers. This capability was used in early telephone repeaters, making long distance phone calls possible in the period before vacuum tubes. These carbon microphones were mechanically coupled with a magnetic telephone receiver.
They are not used for this purpose these days anymore. However they are still used for small things such as walkie talkies and some army radio equipment still contain carbon microphones.
Studio recordings:
Story book recording (vocal recording):
Instrument recording (piano):
Percussion recordings (drums):
Photo Evidence:
.jpeg)
Photo Evidence:
.jpeg)
