Measuring Hearing Protection Devices to ANSI S3.19-1974 Standard

Introduction

This sequence is used to measure the NRR, or Noise Reduction Rating, of a hearing protection device to the ANSI S3.19-1974 standard. NRR is a numerical representation of the sound attenuation of a device. The sequence first measures the response spectrum of the unoccluded hearing protector test fixture, then makes a second measurement with the hearing protection DUT affixed. A signal generator virtual instrument generates the pink noise stimulus while an RTA virtual instrument simultaneously records the A and C weighted noise spectrums. The unoccluded and occluded measurements are analyzed with a series of post-processing steps according to the ANSI S3.19-1974 standard. The final display shows the NRR numerical value, RTA spectra of the left and right side of the unoccluded and occluded hearing test fixture, average attenuation level of the DUT, and the standard deviation of the DUT on the test fixture.

The sequence will prompt the user to recall previously saved unoccluded measurements and standard deviation values, saving time if the test fixture and DUT have been measured previously. When a new unoccluded measurement is taken, the user has the option to save these measurements for a future data recall.

Required Software

• SoundCheck 19

Required Hardware

• Hearing Protection Test Fixture or equivalent Head Simulator
• Source Speaker with minimum frequency range of 100hz – 10kHz
• Listen SCM-4 Reference Microphone (Listen p/n 4012) or equivalent (only for calibration)
• Listen AmpConnect ISC (Listen p/n 4042) or equivalent: req. 2-3 input with IEPE power, 1 output

Setup Diagram

Hardware Setup and Calibration

1. Connect the reference microphone to input 1 of the audio interface.
2. Calibrate the reference microphone as instructed in the SoundCheck manual.
3. Position the reference microphone as close to one side of the hearing protector test fixture as possible and calibrate the source speaker as instructed in the SoundCheck manual.
4. Disconnect the reference microphone and connect the hearing protector test fixture to your audio interface; left side into input 1, right side into input 2

Get Sequence

Download Sequence (zip file)
Download Sequence documentation (PDF)