The document discusses different types of microphones, including their operating principles and common uses. It describes dynamic microphones, which use electromagnetic induction, and capacitor microphones, which can respond to extremely high audio frequencies. Electret condenser microphones contain a permanent charge that induces an AC voltage. Other microphones discussed include ribbon, carbon, crystal, lavalier, shotgun, boom, and location recording microphones.

1. 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

2. 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.
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.

3. Location recording
We had to record in a quiet environment and then a separate recording in a loud environment.
We had to explain in our recording what we could hear that was making the noises our
recorder was picking up. Then we were asked to analyse the recordings and explain in detail
what was going on in each recording and what was making the noise and compare the
difference between recording in a quiet environment and a loud environment.
Quiet recording in Corridor
Before we begun the recording process, we described where we were recording. This is
probably the most difficult environment to analyse purely for the fact that in the library there
were signs everywhere saying “silence please”. The microphone didn’t pick up any speech at
all while we recorded in the library. There were a few of very quiet sounds It picked up like
chairs scraping along the floor. it was a very low pitch and because it was quiet im guessing
the person who was getting out of the chair must have been quite far away from the recorder.
There were a few coughs as well which came out as very deep low pitched voices and
sounding like they were coming from a distance.
Loud environment recording on a road
You can tell a car is approaching because the pitch is deep but the noise is getting
gradually louder and louder until it is right next to us and the car noise is at its
highest volume possible then the volume of the car gradually starts decreasing
more and more until it’s gone. Lorrys require a larger engine to be able to drive
their massive vehicle and cargo at a steady but fast speed which effected our
recordings. The engine of the lorry has a much deeper sound to it than the car that
passed by earlier. I also noted that there was a choking like noise coming from the
engine presumably which I heard the easiest when the Lorry was at its loudest
point (right beside us).