Directional Response

Directional Response

Sensitivity to various angles of incidence with respect to front of the microphone.

Polar patterns - 360° around micTwo main categories:

Omnidirectional Directional

Pressure

Pressure mics respond to differences in sound-pressure waves.

These pressure fluctuations can be picked up from any direction. (Assuming the physical shape of the mic

doesn’t interfere.)

Pressure Mic = Omnidirectional Polar Pattern

Pressure-Gradient

Pressure Gradient mics are responsive to the relative pressure differences between front, back, and sides of a diaphragm.

All directional mics are pressure-gradient.Purely p-g mics are bidirectional (figure 8).

Older ribbon mics

Multiple Directional Patterns

Multiple polar patterns can be obtained from combinations of pressure and pressure-gradient, or from multiple pressure-gradient capsules.

Patterns

Omnidirectional (omni)Bidirectional (figure 8)Cardiod (front)

Super-, Sub- and Hyper-cardiod allow for some rear pickup.

Cardiod

Dynamic mics often achieve directionality through use of rear port. (phase delays)

Condenser mics can use two capsules. In-phase: omni Out of phase: bidirectional Variable stepped combinations to achieve

varied cardiod responses

Cardiod, sub, super-duper and hyper

Cardiod derives its name from the heart-shaped polar pattern.

Super-cardiod allows for a small amount of rear signal to be captured.

Sub-cardiod has a rounded rear pattern.Hyper-cardiod allows for greater sensitivity

to rear signals, with a wider rear pattern. (approaches bidirectional)

Frequency Response Curve

Measured on-axis, output plotted in dB Measurement of output over audible frequency

range when given a constant signal. Off-axis plots sometimes included Flat response (no output variation across

frequency range) More common to have some emphasis or de-

emphasis. De/emphasis can occur due to preamp stage,

diaphragm characteristics, tube resonance, windscreen design, etc.

Proximity Effect

All directional microphones exhibit proximity effect.

Low-frequency boost when close to source.

When source is close, gradient properties diminish, with low frequencies favored.