The usable techniques can be:

• Noise measurement: carried out with one or more microphones, amplifier, digitalization and SW signal conditioning.
  The measurement is performed in an anechoic (or, at minimum, acoustically insulated) chamber; the piece is put into operation and one or more microphones measure the sound pressure generated. In the past, the techniques relied on the (auditory) sensitivity of the operator who physically listened to the piece being tested; nowadays, we generally use band SW filtering, where the bandwidth can be set in the recipe, the control is done downstream of an acquisition made in the time domain and the RMS level is assessed:
  • Acquisition of 1 or more microphones
  • Amplification, ad hoc card
  • Digitizer: 48KS, 48000 Samples
  • Processing:
    • Multi-band programmable band pass filter (3—5)
    • Measurement of the RMS value per band, as an alternative measure of the average value
    • Comparison with maximum permissible threshold values.

• Vibration measurement: performed using one or more accelerometers, mounted on the piece, relative amplification, digitization and signal conditioning.
  It is the most commonly used technique. The subsequent conditioning can be:
  • Time domain analysis: as for microphone acquisition, alternative use of an accelerometer.
  • Frequency domain analysis:
    • Use of 1 or more accelerometers
    • Passband limited at the bottom by the acquisition time, at the top by the Sample Rate
    • Assessment Fmin= 1/tacq, Fmax=Fsamples/2, except for HW sensor characteristics
    • Acquisition by digitizer and Fourrier analysis, result rendered in dBfs
    • Division of the spectrum into freely settable bands, usually 4 or 5
    • Acceptance according to the maximum level recorded per band