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  1. Acoustics
  2. AKG Acoustics
  3. Audio feedback
  4. Audio level compression
  5. Audio quality measurement
  6. Audio-Technica
  7. Balanced audio connector
  8. Beyerdynamic
  9. Blumlein Pair
  10. Capacitor
  11. Carbon microphone
  12. Clipping
  13. Contact microphone
  14. Crosstalk measurement
  15. DB
  16. Decibel
  17. Directional microphone
  18. Dynamic range
  19. Earthworks
  20. Electret microphone
  21. Electrical impedance
  22. Electro-Voice
  23. Equal-loudness contour
  24. Frequency response
  25. Georg Neumann
  26. Harmonic distortion
  27. Headroom
  28. ITU-R 468 noise weighting
  29. Jecklin Disk
  30. Laser microphone
  31. Lavalier microphone
  32. Loudspeaker
  33. M-Audio
  34. Microphone
  35. Microphone array
  36. Microphone practice
  37. Microphone stand
  38. Microphonics
  39. Nevaton
  40. Noise
  41. Noise health effects
  42. Nominal impedance
  43. NOS stereo technique
  44. ORTF stereo technique
  45. Parabolic microphone
  46. Peak signal-to-noise ratio
  47. Phantom power
  48. Pop filter
  49. Positive feedback
  50. Rode
  51. Ribbon microphone
  52. Schoeps
  53. Sennheiser
  54. Shock mount
  55. Shure
  56. Shure SM58
  57. Signal-to-noise ratio
  58. Soundfield microphone
  59. Sound level meter
  60. Sound pressure
  61. Sound pressure level
  62. Total harmonic distortion
  63. U 47
  64. Wireless microphone
  65. XLR connector



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Sound level meter

From Wikipedia, the free encyclopedia

Integrating sound level meter in dB(A)
Integrating sound level meter in dB(A)

A sound level meter is used to measure sound levels, usually in terms of subjective loudness. This involves the use of a weighting filter, usually to the A-weighting standard.

The use of A-weighting is historical, and not really justifiable on the basis of current understanding of equal-loudness contours and the fact that these have been shown not to apply for random noise. The use of an rms rectifier, also standard, is also hard to justify.

Sound level meters are commonly used in noise pollution studies for the assessment of roadway noise, industrial noise, and aircraft noise. Strictly speaking the A-weighting was only recommended for quiet sounds in the region of 40 dB SPL but today it is used at all levels, and the other weightings are little used, except for D-weighting which is used specifically for Aircraft noise at very high levels.

Sound exposure meters use the same principles, and A-weighting, to measure total exposure to noise over a period of time. The result is indicated in terms of LAeqT, which means the equivalent level (A weighted) over a time period T (often 8 hours). The equivalent level is derived by storing a large number of sound pressure values in pascals and then calculating the mean square before converting to dB SPL. High levels thus count more in the final figure. Exposure meters are usually used to assess high level industrial noise, in terms of potential for hearing damage, though they use the A-weighting curve which was derived from equal-loudness contours at very low level(40 dB SPL).

The ITU-R 468 noise weighting curve was designed specifically for noise measurement, along with a quasi-peak detector, and though used mostly for professional audio equipment measurements, would actually produce more meaningful results if incorporated into sound level meters for low level noise measurement.

The following standards define sound level meters and exposure meters:

  • BS 3539:1986 "Sound level meters for the noise emitted by motor vehicles"
  • BS 5969:1981 "Sound level meters"
  • BSEN 60651:1994 "Sound level meters" - superseded BS 5969
  • BS 6402:1983 "Personal sound exposure meter" - for measuring LAeq

See also

  • Equal-loudness contour
  • Noise
  • Noise pollution
  • Noise regulation
  • ITU-R 468 noise weighting
  • Weighting filter
  • Audio quality measurement
  • Fletcher-Munson curves
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