Week 8: Microphone patterns; stereo microphone techniques

We use a degree chart to plot out the directionality of a microphone. 0 degrees is "on axis" which means that the SPL is going directly into the diaphragm.

Polar Response

Directionality

Pickup-pattern
 * Omni-directional - These Mics are capable of picking up sound from all directions. Do not exhibit proximity effect.
 * Cardioid - Has a 130 degree visible angle before substantial attenuation. 180 degrees is known as the null angle. (Shure SM 57)
 * Super-Cardioid - Has about a 115 degree visible angle before substantial attenuation. Though it does have slight pickup from 180 degrees. (Beta 57)
 * Hyper-cardiod - Has a 105 degree visible angle before substantial attenuation. However it has a large area of pickup out the back.
 * Bi-directional (Figure 8) - Equally sensitive at 0 degrees and 180 degrees with a null pattern at both 90 degrees.
 * Shotgun (Ultra-Directional) - A mic that can go down to a 25 degree pattern.

Proximity effect

Front address vs. Side address

Frequency response

Curved (Colored response)

Flat Responses: The microphone produces voltage as close to unity gain over most of the frequencies.

Sensitivity - The measurement of the electrical output of the mic based on a standardized sound level. Measured in millivolt per pascal

Linearity - How much SPL it can handle before the microphone distorts. Anything under 100 dB is bad. Looking for above 150dB

ENR (Equivilent noise rating) - How much self-noise the Micraphone itself makes, measured in dB. You are wanting below 20 - 25 dB. The 15 -20 dB range is getting good, below 15 dB is great.