independent testing
National Acoustic Laboratories Testing
Objective measurements of Earasers attenuation across seven frequencies, conducted by the National Acoustic Laboratories.
NAL ATTENUATION TESTING
The National Acoustic Laboratories independently tested Earasers for real-ear attenuation in July 2017. The testing measured attenuation across seven frequencies from 125 Hz to 8 kHz and evaluated two Earasers models.
Mean Attenuation by Frequency
| Frequency | Earasers -17 dB Avg | Earasers -19 dB Peak |
|---|---|---|
| 125 Hz | 4.6 dB | 3.4 dB |
| 250 Hz | 5.4 dB | 4.0 dB |
| 500 Hz | 7.8 dB | 6.0 dB |
| 1 kHz | 8.9 dB | 8.0 dB |
| 2 kHz | 16.1 dB | 16.5 dB |
| 4 kHz | 19.1 dB | 18.6 dB |
| 8 kHz | 13.1 dB | 14.1 dB |
Mean real-ear attenuation reported by the National Acoustic Laboratories (NAL).
How the Testing Was Conducted
NAL recruited 20 adult test subjects for each Earasers device. All subjects completed a hearing test to determine eligibility before testing. Each subject's hearing thresholds were measured without hearing protection and then again with the Earasers fitted using the manufacturer's instructions. The difference between these measurements was used to determine real-ear attenuation.
What Was Measured
The testing measured real-ear attenuation across seven frequencies from 125 Hz through 8 kHz. For each subject, NAL established an open-ear reference threshold and then measured the threshold with the earplugs fitted. The difference between those measurements provided the real-ear attenuation at each frequency.
NAL Test Results
The NAL report provides mean attenuation measurements at each test frequency, along with the standard deviation and two single-number attenuation ratings: SLC80 and SNR. For both Earasers models, the reported SLC80 was 6 dB. The reported SNR was 13.1 for Earasers -17 dB Avg and 12.3 for Earasers -19 dB Peak.
At 4 kHz, mean attenuation was 19.1 dB for Earasers -17 dB Avg and 18.6 dB for Earasers -19 dB Peak. At 8 kHz, the corresponding mean attenuation values were 13.1 dB and 14.1 dB. The report provides measurements across all seven test frequencies from 125 Hz through 8 kHz.
Testing Conditions
The testing used calibrated equipment and controlled acoustic procedures. Before attenuation testing, the Earasers devices underwent a dry-heat test in accordance with AS/NZS 1270, with the temperature increased to 50°C and maintained for at least 16 hours. The devices were visually inspected before and after testing, and the report states that neither Earasers device showed evidence of mechanical failure during testing.
During the attenuation measurements, subjects were tested individually using controlled sound signals at seven octave-band frequencies from 125 Hz through 8 kHz. Subjects fitted the earplugs using the information and instructions supplied by the manufacturer.
Understanding the Results
The NAL results are statistical measurements and should not be interpreted as a guarantee of the same attenuation for every individual user. The report notes that the SLC80 calculation incorporates the variability measured among test subjects by using the mean attenuation minus one standard deviation. NAL states that this calculation is intended to represent the stated level of attenuation for 80% of user/noise-spectrum combinations.
The frequency-by-frequency results are also useful because attenuation was not identical across the tested frequency range. The NAL report provides the mean attenuation, standard deviation and mean-minus-standard-deviation values at each of the seven test frequencies.
Earasers earplugs underwent independent attenuation testing by the National Acoustic Laboratories (NAL) in July 2017. The testing evaluated Earasers -17 dB Avg and Earasers -19 dB Peak using real-ear attenuation measurements conducted in accordance with AS/NZS 1270:2002 Acoustics – Hearing Protectors. The NAL report notes that the results are statistical and do not apply directly to every individual.