ISO 5347-15:1993

Overview

ISO 5347-15:1993 specifies methods for testing the acoustic sensitivity of accelerometers as part of the ISO 5347 series on calibration of vibration and shock pick-ups. It lays down detailed instrumentation, environmental conditions and procedural steps to measure how an accelerometer responds when exposed to acoustic (air‑borne) sound fields. The procedure applies to random noise in the 125 Hz to 8 000 Hz band at a reference sound pressure level of 130 dB (reference: 2 × 10^-5 Pa).

Key topics and technical requirements

• Scope: Applies specifically to accelerometers and acoustic‑sensitivity testing within the given frequency and level range.
• Environmental control: Ambient temperature recommended at 23 °C ± 3 °C.
• Test room: Minimum volume 75 m³ to approximate free‑field acoustic conditions.
• Acoustic source and setup:
  • Random‑noise generator with octave‑band filtering, amplifier and wide‑band loudspeaker.
  • Speaker positioned mid‑room with no hard reflecting surface directly in front; 50–100 mm distance from speaker to accelerometer recommended for the deflector setup.
  • Suggested audio equipment examples (from the standard): low‑pass filter, 30 W power amplifier, 50 W loudspeaker in a 1 m × 1 m baffle.
• Reference sound pressure spectrum (per octave band):
  • 125 Hz: 115 dB ± 6 dB
  • 250 Hz to 2 000 Hz: 120 dB ± 5 dB
  • 4 000 Hz: 115 dB ± 6 dB
  • Overall target: 130 dB ± 5 dB (reference 2 × 10^-5 Pa)
• Acoustic level measurement: Use an SPL meter with octave‑band filtering covering 80–140 dB and maximum uncertainty ±3 dB.
• Mounting & measurement procedure:
  • Suspend the accelerometer on rubber cords with suspension resonance < 20 Hz; rotate to find maximum sensitivity.
  • Replace the accelerometer with a microphone to establish the noise spectrum, then reinstall the accelerometer and record the maximum output (in m/s²) for the specified SPL.
• Special procedures:
  • If rigid‑body motion of the whole accelerometer is suspected (affecting results), mount the sensor on a small, very heavy fixed object and measure induced motion with a protected internal accelerometer to subtract induced components.
  • For minimizing structural motion, mount on a short rigid rod embedded in a heavy foundation (high density materials such as tungsten are suggested).
• Notes: Piezoelectric accelerometers may present measurement challenges due to whole‑body vibration effects; special methods are given when this is suspected.

Applications and users

ISO 5347-15 is used by:

• Calibration and metrology laboratories performing accelerometer and vibration sensor calibration
• Sensor manufacturers validating acoustic immunity / sensitivity
• Test engineers in aerospace, automotive, industrial and civil vibration testing who need to quantify sensor response to acoustic fields
• Quality assurance and compliance teams integrating sensor performance specifications

Practical uses include verifying that accelerometers meet required immunity levels for acoustic environments and ensuring accurate vibration measurement where air‑borne sound might contaminate results.

Related standards

Part of the ISO 5347 series (methods for calibration of vibration and shock pick-ups) - see other parts (e.g., Part 0, Part 1, Part 2, Part 3, Part 11, Part 12, Part 16, etc.) for complementary calibration and environmental sensitivity tests.

Keywords: ISO 5347-15, acoustic sensitivity, accelerometer calibration, vibration sensor test, sound pressure 130 dB, 125–8000 Hz, acoustic immunity.