The Ultimate Guide to Contact Microphones: From Theory to Practice

Introduction

Contact microphones, also known as piezo contact microphones, are unique and versatile devices that transform sound vibrations directly into electrical signals. Unlike traditional microphones, which rely on air pressure fluctuations, contact mics sense vibrations through direct contact with the sound source. This unique characteristic opens up a world of possibilities for capturing sounds that would otherwise be inaccessible to traditional mics.

Working Principle

Contact microphones consist of a piezoelectric element, typically lead zirconate titanate (PZT), sandwiched between two conductive plates. When the element is subjected to mechanical vibrations, it generates an electrical signal proportional to the force applied. The electrical signal can then be amplified and processed to extract the desired sound.

Applications

Contact microphones have found widespread applications in various fields, including:

• Musical instrument pickup: Amplifying acoustic instruments such as guitars, violins, and drums.
• Ambient sound recording: Capturing subtle sounds from objects, environments, and the body.
• Industrial monitoring: Detecting vibrations in machinery, structures, and equipment.
• Forensic investigations: Analyzing vibrations for sound and vibration analysis.
• Medical diagnostics: Monitoring heart murmurs, breathing, and other body sounds.

Types of Contact Microphones

Contact microphones come in various forms, each with its own advantages and applications:

Advantages of Contact Microphones

Contact microphones offer several advantages over traditional microphones:

• Extended frequency response: Capable of capturing a wider range of frequencies, including sub-bass and high-frequency transients.
• High sensitivity: Can detect even the slightest vibrations.
• Precise localization: Allows for accurate sound source identification.
• Compact size and portability: Ideal for situations where space is limited.
• Durability: Less susceptible to damage compared to traditional microphones.

How to Use Contact Microphones

Using contact microphones is relatively straightforward, but here are some tips to ensure optimal results:

• Choose the right microphone: Select a microphone type that suits the specific application and sound source.
• Position the microphone: Experiment with different placement techniques to find the best position for capturing the desired sound.
• Secure the microphone: Use adhesive tape, elastic bands, or microphone clips to ensure the microphone remains in place.
• Use a preamplifier: If the microphone's output signal is weak, consider using a preamplifier to boost the signal.
• Record in a quiet environment: Minimize background noise to maximize the clarity of the recorded sound.

Step-by-Step Guide to Contact Microphone Recording

1. Prepare your microphone: Choose and position the appropriate microphone for your sound source.
2. Connect the microphone: Connect the microphone to a preamplifier or audio recorder.
3. Set the gain: Adjust the gain setting on the preamplifier to optimize the signal level.
4. Record the sound: Press the record button and capture the desired sound.
5. Monitor the recording: Listen to the recording to ensure the desired sound is being captured.
6. Adjust the microphone position or gain: If necessary, adjust the microphone position or gain to improve the sound quality.

Common Mistakes to Avoid

• Overtightening the microphone: Excessive pressure on the piezoelectric element can damage the microphone.
• Using the microphone in a wet environment: Contact microphones are not waterproof and should be protected from moisture.
• Overloading the microphone: High levels of sound pressure can overload the microphone, resulting in distortion.
• Using a low-quality preamplifier: A poor-quality preamplifier can degrade the signal качество and introduce noise.
• Ignoring background noise: Ensure to record in a quiet environment to avoid capturing unwanted background sounds.

FAQs

1. What is the difference between a piezo contact microphone and a condenser microphone?

• Piezo contact microphones transform vibrations directly into electrical signals, while condenser microphones use air pressure fluctuations.

2. What is the typical frequency response of a contact microphone?

• Contact microphones typically have a frequency response ranging from 20 Hz to 20 kHz or higher.

3. How far away from the sound source should I place a contact microphone?

• The optimal distance depends on the microphone type and sound source, but generally, closer placement results in higher sensitivity.

4. Can I use a contact microphone to record underwater?

• No, contact microphones are not waterproof and should not be used in wet environments.

5. What is the best way to attach a contact microphone to a musical instrument?

• Use adhesive tape, elastic bands, or microphone clips to secure the microphone to the instrument.

6. How do I troubleshoot a contact microphone that is not working?

• Check the microphone connections, preamplifier settings, and ensure the microphone is not damaged.

Conclusion

Contact microphones are versatile and powerful tools that can capture unique and expressive sounds from a wide range of sources. By understanding the working principle, types, applications, and usage techniques, you can harness the full potential of these microphones to enhance your sound recording and sound design projects.