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Microphones

Transducer

 

 

  • Dynamic (moving-coil)
  • Condenser
  • Capacitor or electrostatic
  • Carbon
  • Piezoelectric
  • Fiber optic
  • Laser liquid
  • MEMS technology

Applications

 

 

  • Telecommunication
  • Consumer
  • Multimedia and professional applications

Particularities

Microphones can be modeled at low frequencies by equivalent network comprising lumped elements with linear and nonlinear parameters. At higher frequencies, a model with distributed parameters is required. Due to the low mass of the diaphragm, the air has a significant influence on the mechanical vibration. Additional acoustical elements (cavities, ducts, damping material) are used to obtain a desired amplitude response. 
The stiffness of the mechanical suspension and acoustical damping are the dominant causes of nonlinear distortion in most microphones. The nonlinearities of dynamic microphones can be identified by using an electrical excitation and by measuring the voltage and current at the terminals. A measurement performed in vacuum shows the mechanical elements without the influence of air load. Mechanical vibration measured by laser scanning techniques is the basis for modal analysis.


Critical Issues

  • Internal noise
  • Maximal peak SPL
  • Flatness of the amplitude response on-axis
  • Desired directivity

Standards

American National Standards Institute
ANSI S3.7 Method for Coupler Calibration of Earphones
ANSI S3.22 Specification of Hearing Aid Characteristics
ANSI S3.25 Standard for an Occluded Ear Simulator

Institute of Electrical and Electronics Engineers
IEEE 269 Standard Methods for Measuring Transmission Performance of Analog and Digital telephone Sets, Handsets, and Headsets
IEEE 1329 Standard Method for Measuring Transmission Performance of Handsfree Telephone Sets

International Telecommunication Union
ITU-T Recommendation P.79 Telephone Transmission Quality, Measurements related to speech loudness


Most relevant Measurements 

Modules of R&D SYSTEM

Modules of QC SYSTEM

Linear parameters
(T/S, creep, inductance)

Linear Parameter Measurement (LPM)

Impedance Task (IMP)
Motor + Suspension Check (MSC)

Nonlinear parameters (only dynamic microphones)

Large Signal Identification (LSI Tweeter)

Motor + Suspension Check (MSC)

Mechanical parameters (without air load)

 

 

Rub & Buzz and other irregular defects

Transfer Function Measurement (TRF PRO)

Standard System
Meta Hearing Technology (MHT)

 

Amplitude response
(sensitivity, mean SPL, polarity)

Transfer Function Measurement (TRF)
3D-Distortion Measurement (DIS)

Basic System
Standard System

Nonlinear harmonic distortion
(THD, components)

Transfer Function Measurement (TRF)
3D-Distortion Measurement (DIS)

Basic System
Standard System

Intermodulation distortion (IMD)

3D-Distortion Measurement (DIS)

 

Amplitude intermodulation distortion (AMD)
(modulation of the fundamental)

3D-Distortion Measurement (DIS PRO)

 

Thermal and nonlinear compression
(fundamental, harmonics, dc displacement)

3D-Distortion Measurement (DIS)

 

Peak displacement
DC displacement

3D-Distortion Measurement (DIS)
Transfer Function Measurement (TRF)
Large Signal Identification (LSI)

 

Multi-tone distortion

Linear Parameter Measurement (LPM)
Multi-Tone Measurement (MTON)

 

Phase response

Transfer Function Measurement (TRF)

Sound Pressure Task (SPL)
Sound Pressure and Impedance Task (SPL-IMP) 

Minimal-phase, excess-phase, group delay

Transfer Function Measurement (TRF)

 

Time-frequency analysis (Wigner, cumulative decay spectrum, sonagraph, wavelet, …)

Transfer Function Measurement (TRF)

 

Distortion generated by dominant nonlinearities
Bl(x), Cms(x), Le(x), Rms(v) in reproduced audio signal

Simulation-Auralization (SIM-AUR)
Large Signal Identification (LSI)
Power Testing (PWT)

 

Accumulated acceleration level (AAL)

Scanning Vibrometer System (SCN)

 

Modal analysis and decomposition techniques to find
circumferential, radial components and rocking modes

Scanning Vibrometer System (SCN)
Rocking Mode Analysis (RMA)
Higher Modal Analysis (HMA)

 

Radiation analysis
(sound pressure on-axis, directivity index, sound power)

Scanning Vibrometer System (SCN)

 

Auralization (only dynamic microphones)

Simulation-Auralization (SIM-AUR)