BS 6840-4:1997

1 Scope
2 Normative references
3 General conditions
    3.1 General
    3.2 Measurement conditions
          3.2.1 Introduction
          3.2.2 Rated conditions
4 Particular conditions
    4.1 Pre-conditioning
    4.2 Sound source
    4.3 Measurement of sound pressure
    4.4 Voltage measuring system
    4.5 Acoustical environment
          4.5.1 General
          4.5.2 Free-field conditions
          4.5.3 Diffuse-field conditions
          4.5.4 Microphone coupled to a sound source by
                  means of a small cavity coupler
    4.6 Methods of taking frequency response curves
          4.6.1 Point-by-point or continuous sweep frequency
                  method
          4.6.2 Calibration methods
    4.7 Overall accuracy
5 Type description (acoustical behaviour)
    5.1 Principle of the transducer
    5.2 Type of microphone
    5.3 Type of directional response characteristics
6 Terminals and controls
    6.1 Marking
    6.2 Connectors and electrical interface values
7 Reference point and axis
    7.1 Reference point
    7.2 Reference axis
8 Rated power supply
    8.1 Characteristic to be specified
    8.2 Method of measurement
9 Electrical impedance
    9.1 Internal impedance
          9.1.1 Characteristic to be specified
          9.1.2 Methods of measurement
    9.2 Rated impedance
    9.3 Minimum permitted load impedance
10 Sensitivity
    10.1 General
    10.2 Sensitivities with respect to acoustical environment
          10.2.1 Free-field sensitivity
          10.2.2 Diffuse-field sensitivity
          10.2.3 Close-talking sensitivity
          10.2.4 Pressure sensitivity
    10.3 Sensitivities with respect to acoustical environment
          10.3.1 Related sensitivity
          10.3.2 Characteristic sensitivity for speech
11 Response
    11.1 Frequency response
          11.1.1 Characteristics to be specified
          11.1.2 Method of measurement
    11.2 Effective frequency range
          11.2.1 Characteristic to be specified
          11.2.2 Method of measurement
12 Directional characteristics
    12.1 Directional pattern
          12.1.1 Characteristic to be specified
          12.1.2 Methods of measurement
    12.2 Directivity index
          12.2.1 Characteristic to be specified
          12.2.2 Method of measurement
    12.3 Front-to-rear sensitivity index (0 deg - 180 deg)
          12.3.1 Characteristic to be specified
          12.3.2 Method of measurement
13 Amplitude non-linearity
    13.1 General
    13.2 Total harmonic distortion
          13.2.1 Characteristics to be specified
          13.2.2 Method of measurement
    13.3 Harmonic distortion of the nth order (N = 2.3.)
          13.3.1 Characteristic to be specified
          13.3.2 Method of measurement
    13.4 Difference frequency distortion of second order
          13.4.1 Characteristic to be specified
          13.4.2 Method of measurement
14 Limiting characteristics
    14.1 Rated maximum permissible peak sound pressure
    14.2 Overload sound pressure
          14.2.1 Characteristic to be specified
          14.2.2 Method of measurement
15 Balance
    15.1 Balance of the microphone output
    15.2 Balance under working conditions
16 Equivalent sound pressure level due to inherent noise
    16.1 Characteristic to be specified
    16.2 Method of measurement
17 Ambient conditions
    17.1 Pressure range
    17.2 Temperature range
    17.3 Relative humidity range
18 External influences
    18.1 General
          18.1.1 Specification and measuring methods
          18.1.2 Other external interferences
    18.2 Equivalent sound pressure due to external magnetic
          fields
          18.2.1 Characteristic to be specified
          18.2.2 Method of measurement
    18.3 Equivalent sound pressure due to mechanical vibration
          18.3.1 Characteristic to be specified
          18.3.2 Method of measurement
    18.4 Equivalent sound pressure due to wind
          18.4.1 Characteristic to be specified
          18.4.2 Method of measurement
    18.5 Transient equivalent sound pressure due to "pop"
          effort
          18.5.1 Characteristic to be specified
          18.5.2 Method of measurement
    18.6 Equivalent sound pressure due to electromagnetic
          interference
          18.6.1 Characteristic to be specified
          18.6.2 Method of measurement
    18.7 Electrostatic discharge
19 Magnetic stray field
    19.1 Characteristic to be specified
    19.2 Method of measurement
20 Physical characteristics
    20.1 Dimensions
    20.2 Weight
    20.3 Cables and connectors
21 Classification of the characteristics to be specified
    21.1 General
    21.2 Classification
Annexes
A Sound insulation device
B Simplified procedure for "pop"-measurements
C Bibliography