Good Microphone Technique
When addressing a microphone two key points to remember are the angle in which you speak into the microphone, and the use of a "Wind Screen" or "Pop Filter". These two tips will solve almost all microphone addressing problems, A 20 degree turn of your head will avoid most plosive energy from disturbing the microphone element but still direct enough voice energy for the element to capture.
Avoid speaking directly into the microphone element
Speak at an angle into the microphone making use of a windscreen and shock mount
Changing Your Angle
By not speaking head-on into the microphone percussion to the element is greatly
reduced. Speaking head-on creates pressure which is usually beyond the SPL
(Sound Pressure Level) rating of any microphone. This will result in a popping
sound that will cause processing problems.
Use a Windscreen or Pop-Filter
A windscreen or pop-filter is inexpensive and will help deflect concentrated air
from reaching the microphone element by redirecting the air to the sides. The
filter will also capture breath moisture and protect elements from potential
damage.
Use a Solid Base or Adjustable Microphone Boom
An adjustable microphone boom can be beneficial in making your microphone
accessible in many operating positions.
Use a Microphone Shock Mount
A good shock-mount system is designed to prevent vibration from travelling down
the microphone support (boom or base) to the microphone element. Noise from
moving the microphone boom or from human movement in the shack can be avoided by
a good elastic shock mount.
Proximity Effect
"Proximity Effect" is used to describe how sensitive a microphone is to distance
and how the audio changes with distance. Dynamic microphones are more sensitive
to this than others. Proximity effect can be desirable to achieve a certain
up-close warm sound. The optimal distance from the microphone depends on type
and the effect desired.
You should never exceed a distance of more than about 20cm from the microphone. When this distance is exceeded you will need to increase microphone gain to compensate. In this scenario background noise and room reflection pickup will also increase. Even the best microphones will pick up audio energy from the room. A hollow distant sound will be the result.
Microphone Types
Dynamic
The dynamic microphone operates using the electromagnetic principle. This is
similar to an electromechanical loudspeaker. A flexibly-mounted diaphragm is
coupled to a wire coil (voice-coil). The coil is mounted in the air gap of the
magnet (moving freely up and down). Sound striking the diaphragm, the diaphragm
surface vibrates in response. The diaphragm is coupled directly to the coil and
the coil moves too (in the magnetic field). Moving in the magnetic field, an
electrical current is induced in the wire of the coil. The magnitude and
direction of that current is directly related to the motion of the coil, and the
current is an electrical representation of the sound wave. No preamplifier is
needed for this type of microphones.
Dynamic microphones, because of their typically higher SPL ratings can be addressed much closer than their condenser type counterparts. The lips should not touch the microphone head or pop filter and a speaking distance of 3 to 4cm is acceptable. Remember to maintain a 20 degree cross angle to keep the plosive energy from disturbing the microphone element. 5 to 8cm is an ideal distance while maintaining a 20 degree head angle.
Condenser
The condenser microphone is an electrical system that depends on variations in
the internal capacitance (a thin metallic membrane and the stationary back
plate). The diaphragm of the condenser microphone is the negatively charged
plate of the capacitor. Sound waves moving the diaphragm cause a synchronous
change of the capacitance of this capacitor. By moving the plates closer
together, the electrostatic attraction between the plates increases. This causes
a flow of current back to the positive plate and vice versa. As the sound wave
changes, the electrical current changes simultaneously. Gold transducer cases
for optimum conductivity and high resistance to corrosion and humidity are used.
Condenser microphones differ both in design and in the way we should speak into them. Condensers are much more sensitive than dynamics and more susceptible to overload with a typical SPL rating of about 130dB before distortion. Condenser type microphones should be addressed a little further away than dynamic microphones. 30cm is often an acceptable distance, unfortunately it will also pick up the room reflections of your voice and result in a hollow sound. To achieve a close-in sound and reduce room noise a speaking distance of 8 to 15cm is recommended while maintaining about a 20 degree head angle.
Electret Condenser
The electret condenser microphone functions similar to the condenser microphone.
A condenser plate made from an electret material is used to provide the
polarizing voltage. It consists of a very light diaphragm (moving plate) and
back plate (stationary or static plate) and has a permanent charge implanted
into it.
Sound waves moving the diaphragm cause the capacitance between it and the back plate to change synchronously, thus an AC voltage on the back plate is created. They do not require phantom power to charge the diaphragm (like the condenser), but they do require a power supply for their in-microphone preamplifier.
There are three common types of Electret Condenser microphones:
- Foil Electret Condenser Microphones, the electret material is the diaphragm itself
- Back Electret Condenser Microphone, the electret material is the back plate
- Front Electret Condenser Microphone, the electret material is the inside of the case of the microphone
The electret condenser microphone should be operated with the same distance
rules as the regular condenser microphone. (8 to 15cm + 20 degree head angle)
Ribbon Types
When using a ribbon microphone the sound pressure moves a metallic ribbon
arranged in the magnetic field of the microphone head. The movement generates a
voltage between the ends of the ribbon which is proportional to the velocity of
the ribbon. It is also called a "velocity" microphone.
For most ribbon microphones the proximity effect starts to be observed at 2m or less. This can create a full, rich voice for announcers. The main disadvantage to the ribbon microphone is its large size.
A ribbon microphone generally produces a “smooth” sound. This varies from a condenser microphones bolder tighter sound. This variance is due to how their diaphragms are tensioned. A ribbon element is clamped at each end and tensioned lightly - producing a resonant frequency at 50 Hz or below, while condenser microphone diaphragms are tensioned and clamped all around the perimeter, which typically results in a series of high-Q resonances between 8 kHz and 12 kHz. Condenser microphone designers use these peaks to produce an “airiness" and "aggressiveness". The ribbon microphone is smooth and contains natural high and low ends along with excellent transient response.
A typical bi-directional ribbon microphone will have a flat response at a distance of about 2m from the microphone. At shorter distances the bass response increases as distance to the microphone decreases. A ribbon microphone is not recommended for radio use.
The ribbon microphone design first gained popularity in the early 1930s and remained the industry standard for many years.