Traitement du signal

bidirectional pattern

Le Huit : Comprendre les Diagrammes de Prise de Son Bidirectionnels dans les Applications Électriques

Dans le monde de l'enregistrement sonore et de l'ingénierie électrique, les microphones jouent un rôle crucial dans la capture et la transmission des signaux audio. L'une des caractéristiques clés d'un microphone est sa **directionnalité**, qui décrit sa sensibilité au son provenant de différentes directions. Parmi ces schémas, la **bidirectionnelle**, ou "huit", se distingue par ses propriétés directionnelles uniques.

**Le Huit : Une Sensibilité à Deux Faces**

Comme son nom l'indique, un microphone bidirectionnel présente une sensibilité maximale au son provenant de l'avant et de l'arrière de l'appareil, tout en rejetant le son provenant des côtés. Ce motif distinctif, ressemblant au chiffre "8" lorsqu'il est visualisé, en fait un choix idéal pour des scénarios d'enregistrement spécifiques.

**Applications des Microphones Bidirectionnels**

Les microphones bidirectionnels excellent dans les situations où :

  • Capture de Dialogue Concentrée : La sensibilité à l'avant et à l'arrière permet d'isoler des locuteurs spécifiques, ce qui les rend particulièrement utiles pour enregistrer des interviews, des podcasts et des performances live où la capture du dialogue de deux individus se faisant face est cruciale.
  • Enregistrement d'Instruments : Les micros bidirectionnels peuvent être placés stratégiquement pour capturer l'avant et l'arrière des instruments, tels que les guitares ou les batteries, pour un son plus riche et plus nuancé.
  • Enregistrement de Son Ambiant : La capacité à capter les sons à la fois de l'avant et de l'arrière permet de capturer un sentiment d'espace et d'atmosphère, souvent utilisé dans la conception sonore du film et de la vidéo.

Comment ça marche : La Physique derrière le Huit

Le motif bidirectionnel est obtenu grâce à la conception de l'élément du microphone. Dans la plupart des cas, cela implique deux diaphragmes faisant face à des directions opposées. Lorsque les ondes sonores frappent les diaphragmes, elles induisent des signaux électriques qui sont combinés d'une manière qui donne le motif en forme de huit.

Avantages et Inconvénients des Microphones Bidirectionnels

Avantages :

  • Directionnalité Précise : Excellent pour isoler des sources sonores spécifiques et minimiser le bruit indésirable.
  • Reproduction Sonore Naturelle : L'angle de prise de son large peut capturer un sentiment d'espace et de profondeur.

Inconvénients :

  • Sensibilité au Son Hors Axe : Peut capter des sons indésirables provenant des côtés, nécessitant un positionnement précis.
  • Applications Limitée : Ne convient pas à la capture de son provenant de toutes les directions, les rendant moins polyvalents que les micros omnidirectionnels.

Conclusion :

La directionnalité du microphone bidirectionnel, avec sa forme de huit distinctive, présente un outil unique et précieux dans le monde de l'enregistrement sonore et de l'ingénierie électrique. Sa directionnalité précise et sa capacité à capturer le son à la fois de l'avant et de l'arrière en font un outil adapté à des applications spécifiques où une capture sonore précise et nuancée est essentielle. Comprendre les nuances de ce motif permet aux ingénieurs et aux professionnels du son de prendre des décisions éclairées lors du choix du microphone optimal pour leurs besoins.


Test Your Knowledge

Quiz: The Figure Eight Microphone

Instructions: Choose the best answer for each question.

1. What is the most accurate description of a bidirectional microphone's pickup pattern?

a) It picks up sound equally from all directions.

Answer

Incorrect. This describes an omnidirectional microphone.

b) It picks up sound primarily from the front.
Answer

Incorrect. This describes a cardioid microphone.

c) It picks up sound from the front and rear, rejecting sound from the sides.
Answer

Correct! This is the defining characteristic of a bidirectional microphone.

d) It picks up sound from a narrow area in front of the microphone.
Answer

Incorrect. This describes a hypercardioid microphone.

2. Which of the following is NOT a typical application of a bidirectional microphone?

a) Recording an interview with two people facing each other.

Answer

Incorrect. Bidirectional mics are ideal for this situation.

b) Capturing a close-up of a drum solo.
Answer

Incorrect. Bidirectional mics can effectively capture the front and back of instruments.

c) Recording a large orchestra in a concert hall.
Answer

Correct! Bidirectional mics are not suitable for capturing a wide range of sounds.

d) Recording the sound of wind blowing through trees for a nature documentary.
Answer

Incorrect. Bidirectional mics can be used to capture ambient sounds, including wind.

3. What is the main advantage of using a bidirectional microphone for recording dialogue?

a) Its ability to pick up sound from all directions.

Answer

Incorrect. This is not an advantage of a bidirectional microphone.

b) Its ability to isolate specific speakers.
Answer

Correct! The focused pickup pattern minimizes unwanted noise.

c) Its ability to capture a wide range of frequencies.
Answer

Incorrect. This is not a characteristic specific to bidirectional microphones.

d) Its ability to produce a very loud sound.
Answer

Incorrect. The pickup pattern does not affect the microphone's output volume.

4. What is the primary reason why bidirectional microphones are not suitable for all recording situations?

a) They are very expensive.

Answer

Incorrect. Bidirectional microphones are available at various price points.

b) They are not very sensitive to sound.
Answer

Incorrect. Bidirectional microphones can be very sensitive.

c) They are sensitive to off-axis sound, which can introduce unwanted noise.
Answer

Correct! The sensitivity to sound from the sides can be problematic in certain situations.

d) They are not very durable.
Answer

Incorrect. The microphone's pickup pattern does not determine its durability.

5. Which of the following best describes the principle behind the figure eight pickup pattern?

a) A single diaphragm that vibrates in response to sound waves.

Answer

Incorrect. This describes a simple microphone design.

b) Two diaphragms facing opposite directions, their signals combined to create the pattern.
Answer

Correct! This is the typical design for a bidirectional microphone.

c) A complex electronic circuit that filters out unwanted sound.
Answer

Incorrect. While some filtering might occur, the pattern is primarily a result of the microphone design.

d) A special material that absorbs sound from the sides.
Answer

Incorrect. This is not how the figure eight pattern is achieved.

Exercise: Microphone Placement

Scenario: You are recording a podcast with two guests sitting across from each other at a table. You have a bidirectional microphone available.

Task: Describe the optimal placement of the microphone to capture both guests' voices clearly, minimizing unwanted background noise. Explain your reasoning.

Exercice Correction

The optimal placement for the microphone would be directly above the center of the table, pointing downwards. This is because: * **Focused Pickup:** The bidirectional pattern will pick up the guests' voices from the front and rear of the microphone, ensuring that both voices are captured equally. * **Minimized Noise:** Positioning the microphone above the table reduces the likelihood of picking up unwanted noise from the sides, such as keyboard clicks or rustling papers. * **Equal Distance:** Placing the microphone in the center ensures that both guests are at an equal distance from the microphone, resulting in a balanced sound recording. This placement leverages the strengths of the bidirectional microphone to achieve a clear and professional-sounding podcast recording.


Books

  • Recording Engineering for Film, Television and Digital Media by David Miles Huber: This comprehensive textbook covers various aspects of sound recording, including microphone pickup patterns.
  • The Microphone Book by Glen Ballou: This book offers a detailed exploration of microphones and their characteristics, with dedicated chapters on different pickup patterns.
  • Sound Recording: The Art & Science of Sound Recording, Mastering, and Production by Tom Kenny: This book covers microphone theory and techniques, including sections on directional microphones.

Articles

  • Understanding Microphone Pickup Patterns: A Guide to the Most Common Types by SoundGuys: A simple and informative article explaining various microphone pickup patterns, including bidirectional, with diagrams.
  • Microphone Polar Patterns: A Guide to Choosing the Right Microphone by Sweetwater Sound: This article provides a detailed overview of different microphone pickup patterns, their advantages, and application scenarios.
  • Choosing the Right Microphone: A Comprehensive Guide by Music Critic: This guide includes a section on directional microphones and how to choose the best one for your needs.

Online Resources

  • Microphone Pickup Patterns by Wikipedia: A comprehensive overview of different microphone pickup patterns, with detailed descriptions and illustrations.
  • Microphone Pickup Patterns: A Visual Guide by Sound on Sound: This interactive guide visually explains various microphone pickup patterns, including bidirectional.
  • Microphone Polar Patterns by Audio Mastering: An extensive resource on microphone polar patterns with information on their applications and benefits.

Search Tips

  • "Bidirectional microphone pickup pattern": This will provide a broad range of results covering different aspects of the subject.
  • "figure eight microphone pickup pattern": This more specific search will focus on the unique characteristics of bidirectional microphones.
  • "microphone polar patterns comparison": This search will provide resources comparing different microphone pickup patterns, including bidirectional.
  • "bidirectional microphone applications": This search will highlight various uses of bidirectional microphones in different fields.

Techniques

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