Hearing Protection Measurement

How do you measure hearing protection devices? In this short video, we demonstrate how to measure hearing protection using SoundCheck in accordance with the ANSI S3.19-1974 standard. You’ll see how to set up a head and torso simulator, calibrate the system, and perform repeated unoccluded and occluded measurements using pink noise to accurately calculate attenuation and Noise Reduction Rating (NRR). This method can be used for a wide range of hearing protection devices to ensure reliable and standardized performance testing.

Watch this Video Demo of Measuring Hearing Protection

Learn More about Hearing Protection

• • Measuring Hearing Protection Devices to ANSI S3.19-1974 Standard: https://www.listeninc.com/products/test-sequences/free/noise-cancelling-headphones-test-sequence/

Video Transcript: How to Measure Hearing Protection

In this short video, we’ll measure the performance of hearing protection devices and calculate the Noise Reduction Rating using the ANSI S3.19-standard.

Our setup is simple. We have a head and torso simulator to wear the hearing protectors and capture the signal, a speaker to play the test stimulus, and a calibrated reference microphone for speaker calibration. The stimulus and response signals are transmitted to and from the computer using the AmpConnect 621 audio interface which also contains an amplifier to power the speaker. I also have a SoundConnect 2 to provide 200V polarization voltage to the ears since I’m using an older HATS. The newer versions have pre-polarized ear simulators so they can be powered directly from Listen’s audio interfaces.

We’ll play a pink noise test signal and capture the response with the ears unoccluded. We’ll then put on the hearing protectors and make the occluded measurement. We’ll re-position and re-measure several times and take an average to account for fit variations. We’ll then compare the occluded and unoccluded data to calculate the noise reduction ratio, or NRR.

My reference microphone is already calibrated, and connected to input 1. Now  I need to calibrate the ear simulator input signal paths and source speaker in the calibration editor.

Let’s go to  Setup > Calibration and go to Input Signal paths > Ear Sim L. I have connected this to Input 2, now I’m ready to calibrate the ear. I’m going to use a B&K 4231 calibrator with the coupler UA 1546, hit the calibrate button and save the sensitivity value. Now we’ll repeat that for the other ear, Ear Sim R which is connected to Input 3.. 

Next, I need to calibrate the source speaker. I’ll place the reference mic as close to one side of the hearing protector test fixture as possible. We’ll navigate to the output signal paths tab inside the Calibration editor, and select Source speaker. I’ll make sure it is assigned to Output 3 because that’s the amplifier output of the AmpConnect 621 where we have it connected. Now I’ll click Calibrate using Reference mic as the input. We’ll use a level of 80dBSPL from 10kHz-100Hz, the same frequency range that we’ll use in the sequence. It’s not quite flat, so we’ll iterate a couple more times until the EQ’d response is flat. This looks good. Now, everything is calibrated, we’re ready to run the sequence. 

Let’s hit start.

First, the sequence wants to know how many trials I want to do. We’re going to make this measurement several times, removing the DUT and placing it back so that we can average the response to account for fit variation. We’ll run it 5 times for the purposes of this demo.

First, we’ll capture the unoccluded response – this means measuring the sound levels without any hearing protection in place. The test sequence will play pink noise through the speaker and record the sound spectrum at both ears of the fixture. Let’s hit enter.

Let’s save this measurement.

Now the sequence is asking me to place the hearing protection device onto the test fixture and we’ll continue to repeat the test to measure the occluded response. Now we’ll just follow the instructions and do it four more times.

Next, the sequence performs postprocessing steps on these unoccluded and occluded measurements to calculate the attenuation at different frequencies, average attenuation, standard deviation and finally the Noise Reduction Rating (NRR) – you can see its 26.6 on the left and 32.1 on the right. These measurements provide a complete picture of the device’s performance. 

And that’s it! Using this pre-written sequence – which you can download from our website – it’s quick and easy to  accurately measure attenuation and determine the Noise Reduction Rating of any hearing protection device to the ANSI standard.