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Definition: A bi-directional microphone, also known as a figure-eight microphone, is designed to be most sensitive to sound coming from two opposite directions along one axis while rejecting sound from the sides. This type of microphone captures sound from the front and rear while minimizing noise from the sides.
Detailed Description:
- Polar Pattern:
- Figure-Eight Pattern: The bi-directional microphone has a figure-eight polar pattern, meaning it picks up sound equally well from the front and rear of the microphone. It has a null point (minimal sensitivity) on either side of the microphone.
- Directional Sensitivity: This pattern is useful for recording situations where sound sources are positioned directly in front of and behind the microphone, but not from the sides.
- Applications:
- Interviews: Useful in interviews where the microphone needs to capture the voices of two speakers sitting across from each other.
- Duets and Performances: Ideal for recording duets or performances where sound sources are positioned on opposite sides of the microphone.
- Live Sound: In live sound applications, it can be used to capture sound from the performer while rejecting ambient noise from the sides.
- Design and Construction:
- Microphone Capsule: The bi-directional microphone typically features a diaphragm that responds to sound pressure changes from the front and rear. This design helps achieve the figure-eight polar pattern.
- Acoustic Design: The microphone may include internal acoustic chambers or ports that influence its directional sensitivity and overall performance.
- Advantages:
- Isolation: Provides good isolation of sound sources directly in front of and behind the microphone, reducing the pickup of side noise.
- Balanced Sound: Useful for capturing balanced audio from two sources positioned in front of and behind the microphone.
- Considerations:
- Side Rejection: While it offers excellent front and rear sensitivity, it can pick up unwanted sounds from the sides if not used correctly.
- Placement: Proper placement and orientation are essential to maximize the benefits of the bi-directional pattern and ensure the desired sound sources are captured effectively.
In summary, a bi-directional microphone is a type of microphone with a figure-eight polar pattern that is most sensitive to sound coming from the front and rear while rejecting side noise. It is commonly used in situations where capturing sound from two opposite directions is desired, such as interviews and performances.
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